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 "4.89"
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"
439 .row &_openssl.txt_& "installing a current OpenSSL release"
442 The main specification and the specification of the filtering language are also
443 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
444 &<<SECTavail>>& below tells you how to get hold of these.
448 .section "FTP and web sites" "SECID2"
451 The primary site for Exim source distributions is currently the University of
452 Cambridge's FTP site, whose contents are described in &'Where to find the Exim
453 distribution'& below. In addition, there is a web site and an FTP site at
454 &%exim.org%&. These are now also hosted at the University of Cambridge. The
455 &%exim.org%& site was previously hosted for a number of years by Energis
456 Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge.
460 As well as Exim distribution tar files, the Exim web site contains a number of
461 differently formatted versions of the documentation. A recent addition to the
462 online information is the Exim wiki (&url(http://wiki.exim.org)),
463 which contains what used to be a separate FAQ, as well as various other
464 examples, tips, and know-how that have been contributed by Exim users.
467 An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use
468 this to report bugs, and also to add items to the wish list. Please search
469 first to check that you are not duplicating a previous entry.
473 .section "Mailing lists" "SECID3"
474 .cindex "mailing lists" "for Exim users"
475 The following Exim mailing lists exist:
478 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
479 .row &'exim-users@exim.org'& "General discussion list"
480 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
481 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
484 You can subscribe to these lists, change your existing subscriptions, and view
485 or search the archives via the mailing lists link on the Exim home page.
486 .cindex "Debian" "mailing list for"
487 If you are using a Debian distribution of Exim, you may wish to subscribe to
488 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
491 &url(http://lists.alioth.debian.org/mailman/listinfo/pkg-exim4-users)
493 Please ask Debian-specific questions on this list and not on the general Exim
496 .section "Exim training" "SECID4"
497 .cindex "training courses"
498 Training courses in Cambridge (UK) used to be run annually by the author of
499 Exim, before he retired. At the time of writing, there are no plans to run
500 further Exim courses in Cambridge. However, if that changes, relevant
501 information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/).
503 .section "Bug reports" "SECID5"
504 .cindex "bug reports"
505 .cindex "reporting bugs"
506 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
507 via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure
508 whether some behaviour is a bug or not, the best thing to do is to post a
509 message to the &'exim-dev'& mailing list and have it discussed.
513 .section "Where to find the Exim distribution" "SECTavail"
515 .cindex "distribution" "ftp site"
516 The master ftp site for the Exim distribution is
518 &*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim*&
522 &*ftp://ftp.exim.org/pub/exim*&
524 The file references that follow are relative to the &_exim_& directories at
525 these sites. There are now quite a number of independent mirror sites around
526 the world. Those that I know about are listed in the file called &_Mirrors_&.
528 Within the &_exim_& directory there are subdirectories called &_exim3_& (for
529 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
530 distributions), and &_Testing_& for testing versions. In the &_exim4_&
531 subdirectory, the current release can always be found in files called
534 &_exim-n.nn.tar.bz2_&
536 where &'n.nn'& is the highest such version number in the directory. The two
537 files contain identical data; the only difference is the type of compression.
538 The &_.bz2_& file is usually a lot smaller than the &_.gz_& file.
540 .cindex "distribution" "signing details"
541 .cindex "distribution" "public key"
542 .cindex "public key for signed distribution"
543 The distributions will be PGP signed by an individual key of the Release
544 Coordinator. This key will have a uid containing an email address in the
545 &'exim.org'& domain and will have signatures from other people, including
546 other Exim maintainers. We expect that the key will be in the "strong set" of
547 PGP keys. There should be a trust path to that key from Nigel Metheringham's
548 PGP key, a version of which can be found in the release directory in the file
549 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
550 such as &'pool.sks-keyservers.net'&.
552 At time of last update, releases were being made by Phil Pennock and signed with
553 key &'0x403043153903637F'&, although that key is expected to be replaced in 2013.
554 A trust path from Nigel's key to Phil's can be observed at
555 &url(https://www.security.spodhuis.org/exim-trustpath).
557 Releases have also been authorized to be performed by Todd Lyons who signs with
558 key &'0xC4F4F94804D29EBA'&. A direct trust path exists between previous RE Phil
559 Pennock and Todd Lyons through a common associate.
561 The signatures for the tar bundles are in:
563 &_exim-n.nn.tar.gz.asc_&
564 &_exim-n.nn.tar.bz2.asc_&
566 For each released version, the log of changes is made separately available in a
567 separate file in the directory &_ChangeLogs_& so that it is possible to
568 find out what has changed without having to download the entire distribution.
570 .cindex "documentation" "available formats"
571 The main distribution contains ASCII versions of this specification and other
572 documentation; other formats of the documents are available in separate files
573 inside the &_exim4_& directory of the FTP site:
575 &_exim-html-n.nn.tar.gz_&
576 &_exim-pdf-n.nn.tar.gz_&
577 &_exim-postscript-n.nn.tar.gz_&
578 &_exim-texinfo-n.nn.tar.gz_&
580 These tar files contain only the &_doc_& directory, not the complete
581 distribution, and are also available in &_.bz2_& as well as &_.gz_& forms.
584 .section "Limitations" "SECID6"
586 .cindex "limitations of Exim"
587 .cindex "bang paths" "not handled by Exim"
588 Exim is designed for use as an Internet MTA, and therefore handles addresses in
589 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
590 simple two-component bang paths can be converted by a straightforward rewriting
591 configuration. This restriction does not prevent Exim from being interfaced to
592 UUCP as a transport mechanism, provided that domain addresses are used.
594 .cindex "domainless addresses"
595 .cindex "address" "without domain"
596 Exim insists that every address it handles has a domain attached. For incoming
597 local messages, domainless addresses are automatically qualified with a
598 configured domain value. Configuration options specify from which remote
599 systems unqualified addresses are acceptable. These are then qualified on
602 .cindex "transport" "external"
603 .cindex "external transports"
604 The only external transport mechanisms that are currently implemented are SMTP
605 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
606 transport is available, and there are facilities for writing messages to files
607 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
608 to send messages to other transport mechanisms such as UUCP, provided they can
609 handle domain-style addresses. Batched SMTP input is also catered for.
611 Exim is not designed for storing mail for dial-in hosts. When the volumes of
612 such mail are large, it is better to get the messages &"delivered"& into files
613 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
616 Although Exim does have basic facilities for scanning incoming messages, these
617 are not comprehensive enough to do full virus or spam scanning. Such operations
618 are best carried out using additional specialized software packages. If you
619 compile Exim with the content-scanning extension, straightforward interfaces to
620 a number of common scanners are provided.
624 .section "Run time configuration" "SECID7"
625 Exim's run time configuration is held in a single text file that is divided
626 into a number of sections. The entries in this file consist of keywords and
627 values, in the style of Smail 3 configuration files. A default configuration
628 file which is suitable for simple online installations is provided in the
629 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
632 .section "Calling interface" "SECID8"
633 .cindex "Sendmail compatibility" "command line interface"
634 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
635 can be a straight replacement for &_/usr/lib/sendmail_& or
636 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
637 about Sendmail in order to run Exim. For actions other than sending messages,
638 Sendmail-compatible options also exist, but those that produce output (for
639 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
640 format. There are also some additional options that are compatible with Smail
641 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
642 documents all Exim's command line options. This information is automatically
643 made into the man page that forms part of the Exim distribution.
645 Control of messages on the queue can be done via certain privileged command
646 line options. There is also an optional monitor program called &'eximon'&,
647 which displays current information in an X window, and which contains a menu
648 interface to Exim's command line administration options.
652 .section "Terminology" "SECID9"
653 .cindex "terminology definitions"
654 .cindex "body of message" "definition of"
655 The &'body'& of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message, and is separated from the &'header'& (see
657 below) by a blank line.
659 .cindex "bounce message" "definition of"
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message or a &"non-delivery report"& (NDR). The term
662 &'bounce'& is commonly used for this action, and the error reports are often
663 called &'bounce messages'&. This is a convenient shorthand for &"delivery
664 failure error report"&. Such messages have an empty sender address in the
665 message's &'envelope'& (see below) to ensure that they cannot themselves give
666 rise to further bounce messages.
668 The term &'default'& appears frequently in this manual. It is used to qualify a
669 value which is used in the absence of any setting in the configuration. It may
670 also qualify an action which is taken unless a configuration setting specifies
673 The term &'defer'& is used when the delivery of a message to a specific
674 destination cannot immediately take place for some reason (a remote host may be
675 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
678 The word &'domain'& is sometimes used to mean all but the first component of a
679 host's name. It is &'not'& used in that sense here, where it normally refers to
680 the part of an email address following the @ sign.
682 .cindex "envelope, definition of"
683 .cindex "sender" "definition of"
684 A message in transit has an associated &'envelope'&, as well as a header and a
685 body. The envelope contains a sender address (to which bounce messages should
686 be delivered), and any number of recipient addresses. References to the
687 sender or the recipients of a message usually mean the addresses in the
688 envelope. An MTA uses these addresses for delivery, and for returning bounce
689 messages, not the addresses that appear in the header lines.
691 .cindex "message" "header, definition of"
692 .cindex "header section" "definition of"
693 The &'header'& of a message is the first part of a message's text, consisting
694 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
695 &'Subject:'&, etc. Long header lines can be split over several text lines by
696 indenting the continuations. The header is separated from the body by a blank
699 .cindex "local part" "definition of"
700 .cindex "domain" "definition of"
701 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
702 part of an email address that precedes the @ sign. The part that follows the
703 @ sign is called the &'domain'& or &'mail domain'&.
705 .cindex "local delivery" "definition of"
706 .cindex "remote delivery, definition of"
707 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
708 delivery to a file or a pipe on the local host from delivery by SMTP over
709 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
710 host it is running on are &'remote'&.
712 .cindex "return path" "definition of"
713 &'Return path'& is another name that is used for the sender address in a
716 .cindex "queue" "definition of"
717 The term &'queue'& is used to refer to the set of messages awaiting delivery,
718 because this term is in widespread use in the context of MTAs. However, in
719 Exim's case the reality is more like a pool than a queue, because there is
720 normally no ordering of waiting messages.
722 .cindex "queue runner" "definition of"
723 The term &'queue runner'& is used to describe a process that scans the queue
724 and attempts to deliver those messages whose retry times have come. This term
725 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
726 the waiting messages are normally processed in an unpredictable order.
728 .cindex "spool directory" "definition of"
729 The term &'spool directory'& is used for a directory in which Exim keeps the
730 messages on its queue &-- that is, those that it is in the process of
731 delivering. This should not be confused with the directory in which local
732 mailboxes are stored, which is called a &"spool directory"& by some people. In
733 the Exim documentation, &"spool"& is always used in the first sense.
740 . ////////////////////////////////////////////////////////////////////////////
741 . ////////////////////////////////////////////////////////////////////////////
743 .chapter "Incorporated code" "CHID2"
744 .cindex "incorporated code"
745 .cindex "regular expressions" "library"
748 A number of pieces of external code are included in the Exim distribution.
751 Regular expressions are supported in the main Exim program and in the
752 Exim monitor using the freely-distributable PCRE library, copyright
753 © University of Cambridge. The source to PCRE is no longer shipped with
754 Exim, so you will need to use the version of PCRE shipped with your system,
755 or obtain and install the full version of the library from
756 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
758 .cindex "cdb" "acknowledgment"
759 Support for the cdb (Constant DataBase) lookup method is provided by code
760 contributed by Nigel Metheringham of (at the time he contributed it) Planet
761 Online Ltd. The implementation is completely contained within the code of Exim.
762 It does not link against an external cdb library. The code contains the
763 following statements:
766 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
772 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
773 the spec and sample code for cdb can be obtained from
774 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
775 some code from Dan Bernstein's implementation (which has no license
776 restrictions applied to it).
779 .cindex "SPA authentication"
780 .cindex "Samba project"
781 .cindex "Microsoft Secure Password Authentication"
782 Client support for Microsoft's &'Secure Password Authentication'& is provided
783 by code contributed by Marc Prud'hommeaux. Server support was contributed by
784 Tom Kistner. This includes code taken from the Samba project, which is released
788 .cindex "&'pwcheck'& daemon"
789 .cindex "&'pwauthd'& daemon"
790 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
791 by code taken from the Cyrus-SASL library and adapted by Alexander S.
792 Sabourenkov. The permission notice appears below, in accordance with the
793 conditions expressed therein.
796 Copyright © 2001 Carnegie Mellon University. All rights reserved.
798 Redistribution and use in source and binary forms, with or without
799 modification, are permitted provided that the following conditions
803 Redistributions of source code must retain the above copyright
804 notice, this list of conditions and the following disclaimer.
806 Redistributions in binary form must reproduce the above copyright
807 notice, this list of conditions and the following disclaimer in
808 the documentation and/or other materials provided with the
811 The name &"Carnegie Mellon University"& must not be used to
812 endorse or promote products derived from this software without
813 prior written permission. For permission or any other legal
814 details, please contact
816 Office of Technology Transfer
817 Carnegie Mellon University
819 Pittsburgh, PA 15213-3890
820 (412) 268-4387, fax: (412) 268-7395
821 tech-transfer@andrew.cmu.edu
824 Redistributions of any form whatsoever must retain the following
827 &"This product includes software developed by Computing Services
828 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
830 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
831 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
832 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
833 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
834 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
835 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
836 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
841 .cindex "Exim monitor" "acknowledgment"
844 The Exim Monitor program, which is an X-Window application, includes
845 modified versions of the Athena StripChart and TextPop widgets.
846 This code is copyright by DEC and MIT, and their permission notice appears
847 below, in accordance with the conditions expressed therein.
850 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
851 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
855 Permission to use, copy, modify, and distribute this software and its
856 documentation for any purpose and without fee is hereby granted,
857 provided that the above copyright notice appear in all copies and that
858 both that copyright notice and this permission notice appear in
859 supporting documentation, and that the names of Digital or MIT not be
860 used in advertising or publicity pertaining to distribution of the
861 software without specific, written prior permission.
863 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
864 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
865 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
866 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
867 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
868 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
873 .cindex "opendmarc" "acknowledgment"
874 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
875 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
876 derived code are indicated in the respective source files. The full OpenDMARC
877 license is provided in the LICENSE.opendmarc file contained in the distributed
881 Many people have contributed code fragments, some large, some small, that were
882 not covered by any specific licence requirements. It is assumed that the
883 contributors are happy to see their code incorporated into Exim under the GPL.
890 . ////////////////////////////////////////////////////////////////////////////
891 . ////////////////////////////////////////////////////////////////////////////
893 .chapter "How Exim receives and delivers mail" "CHID11" &&&
894 "Receiving and delivering mail"
897 .section "Overall philosophy" "SECID10"
898 .cindex "design philosophy"
899 Exim is designed to work efficiently on systems that are permanently connected
900 to the Internet and are handling a general mix of mail. In such circumstances,
901 most messages can be delivered immediately. Consequently, Exim does not
902 maintain independent queues of messages for specific domains or hosts, though
903 it does try to send several messages in a single SMTP connection after a host
904 has been down, and it also maintains per-host retry information.
907 .section "Policy control" "SECID11"
908 .cindex "policy control" "overview"
909 Policy controls are now an important feature of MTAs that are connected to the
910 Internet. Perhaps their most important job is to stop MTAs being abused as
911 &"open relays"& by misguided individuals who send out vast amounts of
912 unsolicited junk, and want to disguise its source. Exim provides flexible
913 facilities for specifying policy controls on incoming mail:
916 .cindex "&ACL;" "introduction"
917 Exim 4 (unlike previous versions of Exim) implements policy controls on
918 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
919 series of statements that may either grant or deny access. ACLs can be used at
920 several places in the SMTP dialogue while receiving a message from a remote
921 host. However, the most common places are after each RCPT command, and at the
922 very end of the message. The sysadmin can specify conditions for accepting or
923 rejecting individual recipients or the entire message, respectively, at these
924 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
927 An ACL is also available for locally generated, non-SMTP messages. In this
928 case, the only available actions are to accept or deny the entire message.
930 When Exim is compiled with the content-scanning extension, facilities are
931 provided in the ACL mechanism for passing the message to external virus and/or
932 spam scanning software. The result of such a scan is passed back to the ACL,
933 which can then use it to decide what to do with the message.
935 When a message has been received, either from a remote host or from the local
936 host, but before the final acknowledgment has been sent, a locally supplied C
937 function called &[local_scan()]& can be run to inspect the message and decide
938 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
939 is accepted, the list of recipients can be modified by the function.
941 Using the &[local_scan()]& mechanism is another way of calling external scanner
942 software. The &%SA-Exim%& add-on package works this way. It does not require
943 Exim to be compiled with the content-scanning extension.
945 After a message has been accepted, a further checking mechanism is available in
946 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
947 runs at the start of every delivery process.
952 .section "User filters" "SECID12"
953 .cindex "filter" "introduction"
954 .cindex "Sieve filter"
955 In a conventional Exim configuration, users are able to run private filters by
956 setting up appropriate &_.forward_& files in their home directories. See
957 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
958 configuration needed to support this, and the separate document entitled
959 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
960 of filtering are available:
963 Sieve filters are written in the standard filtering language that is defined
966 Exim filters are written in a syntax that is unique to Exim, but which is more
967 powerful than Sieve, which it pre-dates.
970 User filters are run as part of the routing process, described below.
974 .section "Message identification" "SECTmessiden"
975 .cindex "message ids" "details of format"
976 .cindex "format" "of message id"
977 .cindex "id of message"
982 Every message handled by Exim is given a &'message id'& which is sixteen
983 characters long. It is divided into three parts, separated by hyphens, for
984 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
985 normally encoding numbers in base 62. However, in the Darwin operating
986 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
987 (avoiding the use of lower case letters) is used instead, because the message
988 id is used to construct file names, and the names of files in those systems are
989 not always case-sensitive.
991 .cindex "pid (process id)" "re-use of"
992 The detail of the contents of the message id have changed as Exim has evolved.
993 Earlier versions relied on the operating system not re-using a process id (pid)
994 within one second. On modern operating systems, this assumption can no longer
995 be made, so the algorithm had to be changed. To retain backward compatibility,
996 the format of the message id was retained, which is why the following rules are
1000 The first six characters of the message id are the time at which the message
1001 started to be received, to a granularity of one second. That is, this field
1002 contains the number of seconds since the start of the epoch (the normal Unix
1003 way of representing the date and time of day).
1005 After the first hyphen, the next six characters are the id of the process that
1006 received the message.
1008 There are two different possibilities for the final two characters:
1010 .oindex "&%localhost_number%&"
1011 If &%localhost_number%& is not set, this value is the fractional part of the
1012 time of reception, normally in units of 1/2000 of a second, but for systems
1013 that must use base 36 instead of base 62 (because of case-insensitive file
1014 systems), the units are 1/1000 of a second.
1016 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1017 the fractional part of the time, which in this case is in units of 1/200
1018 (1/100) of a second.
1022 After a message has been received, Exim waits for the clock to tick at the
1023 appropriate resolution before proceeding, so that if another message is
1024 received by the same process, or by another process with the same (re-used)
1025 pid, it is guaranteed that the time will be different. In most cases, the clock
1026 will already have ticked while the message was being received.
1029 .section "Receiving mail" "SECID13"
1030 .cindex "receiving mail"
1031 .cindex "message" "reception"
1032 The only way Exim can receive mail from another host is using SMTP over
1033 TCP/IP, in which case the sender and recipient addresses are transferred using
1034 SMTP commands. However, from a locally running process (such as a user's MUA),
1035 there are several possibilities:
1038 If the process runs Exim with the &%-bm%& option, the message is read
1039 non-interactively (usually via a pipe), with the recipients taken from the
1040 command line, or from the body of the message if &%-t%& is also used.
1042 If the process runs Exim with the &%-bS%& option, the message is also read
1043 non-interactively, but in this case the recipients are listed at the start of
1044 the message in a series of SMTP RCPT commands, terminated by a DATA
1045 command. This is so-called &"batch SMTP"& format,
1046 but it isn't really SMTP. The SMTP commands are just another way of passing
1047 envelope addresses in a non-interactive submission.
1049 If the process runs Exim with the &%-bs%& option, the message is read
1050 interactively, using the SMTP protocol. A two-way pipe is normally used for
1051 passing data between the local process and the Exim process.
1052 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1053 example, the ACLs for SMTP commands are used for this form of submission.
1055 A local process may also make a TCP/IP call to the host's loopback address
1056 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1057 does not treat the loopback address specially. It treats all such connections
1058 in the same way as connections from other hosts.
1062 .cindex "message sender, constructed by Exim"
1063 .cindex "sender" "constructed by Exim"
1064 In the three cases that do not involve TCP/IP, the sender address is
1065 constructed from the login name of the user that called Exim and a default
1066 qualification domain (which can be set by the &%qualify_domain%& configuration
1067 option). For local or batch SMTP, a sender address that is passed using the
1068 SMTP MAIL command is ignored. However, the system administrator may allow
1069 certain users (&"trusted users"&) to specify a different sender address
1070 unconditionally, or all users to specify certain forms of different sender
1071 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1072 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1073 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1074 users to change sender addresses.
1076 Messages received by either of the non-interactive mechanisms are subject to
1077 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1078 (either over TCP/IP, or interacting with a local process) can be checked by a
1079 number of ACLs that operate at different times during the SMTP session. Either
1080 individual recipients, or the entire message, can be rejected if local policy
1081 requirements are not met. The &[local_scan()]& function (see chapter
1082 &<<CHAPlocalscan>>&) is run for all incoming messages.
1084 Exim can be configured not to start a delivery process when a message is
1085 received; this can be unconditional, or depend on the number of incoming SMTP
1086 connections or the system load. In these situations, new messages wait on the
1087 queue until a queue runner process picks them up. However, in standard
1088 configurations under normal conditions, delivery is started as soon as a
1089 message is received.
1095 .section "Handling an incoming message" "SECID14"
1096 .cindex "spool directory" "files that hold a message"
1097 .cindex "file" "how a message is held"
1098 When Exim accepts a message, it writes two files in its spool directory. The
1099 first contains the envelope information, the current status of the message, and
1100 the header lines, and the second contains the body of the message. The names of
1101 the two spool files consist of the message id, followed by &`-H`& for the
1102 file containing the envelope and header, and &`-D`& for the data file.
1104 .cindex "spool directory" "&_input_& sub-directory"
1105 By default all these message files are held in a single directory called
1106 &_input_& inside the general Exim spool directory. Some operating systems do
1107 not perform very well if the number of files in a directory gets large; to
1108 improve performance in such cases, the &%split_spool_directory%& option can be
1109 used. This causes Exim to split up the input files into 62 sub-directories
1110 whose names are single letters or digits. When this is done, the queue is
1111 processed one sub-directory at a time instead of all at once, which can improve
1112 overall performance even when there are not enough files in each directory to
1113 affect file system performance.
1115 The envelope information consists of the address of the message's sender and
1116 the addresses of the recipients. This information is entirely separate from
1117 any addresses contained in the header lines. The status of the message includes
1118 a list of recipients who have already received the message. The format of the
1119 first spool file is described in chapter &<<CHAPspool>>&.
1121 .cindex "rewriting" "addresses"
1122 Address rewriting that is specified in the rewrite section of the configuration
1123 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1124 both in the header lines and the envelope, at the time the message is accepted.
1125 If during the course of delivery additional addresses are generated (for
1126 example, via aliasing), these new addresses are rewritten as soon as they are
1127 generated. At the time a message is actually delivered (transported) further
1128 rewriting can take place; because this is a transport option, it can be
1129 different for different forms of delivery. It is also possible to specify the
1130 addition or removal of certain header lines at the time the message is
1131 delivered (see chapters &<<CHAProutergeneric>>& and
1132 &<<CHAPtransportgeneric>>&).
1136 .section "Life of a message" "SECID15"
1137 .cindex "message" "life of"
1138 .cindex "message" "frozen"
1139 A message remains in the spool directory until it is completely delivered to
1140 its recipients or to an error address, or until it is deleted by an
1141 administrator or by the user who originally created it. In cases when delivery
1142 cannot proceed &-- for example, when a message can neither be delivered to its
1143 recipients nor returned to its sender, the message is marked &"frozen"& on the
1144 spool, and no more deliveries are attempted.
1146 .cindex "frozen messages" "thawing"
1147 .cindex "message" "thawing frozen"
1148 An administrator can &"thaw"& such messages when the problem has been
1149 corrected, and can also freeze individual messages by hand if necessary. In
1150 addition, an administrator can force a delivery error, causing a bounce message
1153 .oindex "&%timeout_frozen_after%&"
1154 .oindex "&%ignore_bounce_errors_after%&"
1155 There are options called &%ignore_bounce_errors_after%& and
1156 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1157 The first applies only to frozen bounces, the second to any frozen messages.
1159 .cindex "message" "log file for"
1160 .cindex "log" "file for each message"
1161 While Exim is working on a message, it writes information about each delivery
1162 attempt to its main log file. This includes successful, unsuccessful, and
1163 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1164 lines are also written to a separate &'message log'& file for each message.
1165 These logs are solely for the benefit of the administrator, and are normally
1166 deleted along with the spool files when processing of a message is complete.
1167 The use of individual message logs can be disabled by setting
1168 &%no_message_logs%&; this might give an improvement in performance on very busy
1171 .cindex "journal file"
1172 .cindex "file" "journal"
1173 All the information Exim itself needs to set up a delivery is kept in the first
1174 spool file, along with the header lines. When a successful delivery occurs, the
1175 address is immediately written at the end of a journal file, whose name is the
1176 message id followed by &`-J`&. At the end of a delivery run, if there are some
1177 addresses left to be tried again later, the first spool file (the &`-H`& file)
1178 is updated to indicate which these are, and the journal file is then deleted.
1179 Updating the spool file is done by writing a new file and renaming it, to
1180 minimize the possibility of data loss.
1182 Should the system or the program crash after a successful delivery but before
1183 the spool file has been updated, the journal is left lying around. The next
1184 time Exim attempts to deliver the message, it reads the journal file and
1185 updates the spool file before proceeding. This minimizes the chances of double
1186 deliveries caused by crashes.
1190 .section "Processing an address for delivery" "SECTprocaddress"
1191 .cindex "drivers" "definition of"
1192 .cindex "router" "definition of"
1193 .cindex "transport" "definition of"
1194 The main delivery processing elements of Exim are called &'routers'& and
1195 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1196 number of them is provided in the source distribution, and compile-time options
1197 specify which ones are included in the binary. Run time options specify which
1198 ones are actually used for delivering messages.
1200 .cindex "drivers" "instance definition"
1201 Each driver that is specified in the run time configuration is an &'instance'&
1202 of that particular driver type. Multiple instances are allowed; for example,
1203 you can set up several different &(smtp)& transports, each with different
1204 option values that might specify different ports or different timeouts. Each
1205 instance has its own identifying name. In what follows we will normally use the
1206 instance name when discussing one particular instance (that is, one specific
1207 configuration of the driver), and the generic driver name when discussing
1208 the driver's features in general.
1210 A &'router'& is a driver that operates on an address, either determining how
1211 its delivery should happen, by assigning it to a specific transport, or
1212 converting the address into one or more new addresses (for example, via an
1213 alias file). A router may also explicitly choose to fail an address, causing it
1216 A &'transport'& is a driver that transmits a copy of the message from Exim's
1217 spool to some destination. There are two kinds of transport: for a &'local'&
1218 transport, the destination is a file or a pipe on the local host, whereas for a
1219 &'remote'& transport the destination is some other host. A message is passed
1220 to a specific transport as a result of successful routing. If a message has
1221 several recipients, it may be passed to a number of different transports.
1223 .cindex "preconditions" "definition of"
1224 An address is processed by passing it to each configured router instance in
1225 turn, subject to certain preconditions, until a router accepts the address or
1226 specifies that it should be bounced. We will describe this process in more
1227 detail shortly. First, as a simple example, we consider how each recipient
1228 address in a message is processed in a small configuration of three routers.
1230 To make this a more concrete example, it is described in terms of some actual
1231 routers, but remember, this is only an example. You can configure Exim's
1232 routers in many different ways, and there may be any number of routers in a
1235 The first router that is specified in a configuration is often one that handles
1236 addresses in domains that are not recognized specially by the local host. These
1237 are typically addresses for arbitrary domains on the Internet. A precondition
1238 is set up which looks for the special domains known to the host (for example,
1239 its own domain name), and the router is run for addresses that do &'not'&
1240 match. Typically, this is a router that looks up domains in the DNS in order to
1241 find the hosts to which this address routes. If it succeeds, the address is
1242 assigned to a suitable SMTP transport; if it does not succeed, the router is
1243 configured to fail the address.
1245 The second router is reached only when the domain is recognized as one that
1246 &"belongs"& to the local host. This router does redirection &-- also known as
1247 aliasing and forwarding. When it generates one or more new addresses from the
1248 original, each of them is routed independently from the start. Otherwise, the
1249 router may cause an address to fail, or it may simply decline to handle the
1250 address, in which case the address is passed to the next router.
1252 The final router in many configurations is one that checks to see if the
1253 address belongs to a local mailbox. The precondition may involve a check to
1254 see if the local part is the name of a login account, or it may look up the
1255 local part in a file or a database. If its preconditions are not met, or if
1256 the router declines, we have reached the end of the routers. When this happens,
1257 the address is bounced.
1261 .section "Processing an address for verification" "SECID16"
1262 .cindex "router" "for verification"
1263 .cindex "verifying address" "overview"
1264 As well as being used to decide how to deliver to an address, Exim's routers
1265 are also used for &'address verification'&. Verification can be requested as
1266 one of the checks to be performed in an ACL for incoming messages, on both
1267 sender and recipient addresses, and it can be tested using the &%-bv%& and
1268 &%-bvs%& command line options.
1270 When an address is being verified, the routers are run in &"verify mode"&. This
1271 does not affect the way the routers work, but it is a state that can be
1272 detected. By this means, a router can be skipped or made to behave differently
1273 when verifying. A common example is a configuration in which the first router
1274 sends all messages to a message-scanning program, unless they have been
1275 previously scanned. Thus, the first router accepts all addresses without any
1276 checking, making it useless for verifying. Normally, the &%no_verify%& option
1277 would be set for such a router, causing it to be skipped in verify mode.
1282 .section "Running an individual router" "SECTrunindrou"
1283 .cindex "router" "running details"
1284 .cindex "preconditions" "checking"
1285 .cindex "router" "result of running"
1286 As explained in the example above, a number of preconditions are checked before
1287 running a router. If any are not met, the router is skipped, and the address is
1288 passed to the next router. When all the preconditions on a router &'are'& met,
1289 the router is run. What happens next depends on the outcome, which is one of
1293 &'accept'&: The router accepts the address, and either assigns it to a
1294 transport, or generates one or more &"child"& addresses. Processing the
1295 original address ceases,
1296 .oindex "&%unseen%&"
1297 unless the &%unseen%& option is set on the router. This option
1298 can be used to set up multiple deliveries with different routing (for example,
1299 for keeping archive copies of messages). When &%unseen%& is set, the address is
1300 passed to the next router. Normally, however, an &'accept'& return marks the
1303 Any child addresses generated by the router are processed independently,
1304 starting with the first router by default. It is possible to change this by
1305 setting the &%redirect_router%& option to specify which router to start at for
1306 child addresses. Unlike &%pass_router%& (see below) the router specified by
1307 &%redirect_router%& may be anywhere in the router configuration.
1309 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1310 requests that the address be passed to another router. By default the address
1311 is passed to the next router, but this can be changed by setting the
1312 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1313 must be below the current router (to avoid loops).
1315 &'decline'&: The router declines to accept the address because it does not
1316 recognize it at all. By default, the address is passed to the next router, but
1317 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1318 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1319 &'decline'& into &'fail'&.
1321 &'fail'&: The router determines that the address should fail, and queues it for
1322 the generation of a bounce message. There is no further processing of the
1323 original address unless &%unseen%& is set on the router.
1325 &'defer'&: The router cannot handle the address at the present time. (A
1326 database may be offline, or a DNS lookup may have timed out.) No further
1327 processing of the address happens in this delivery attempt. It is tried again
1328 next time the message is considered for delivery.
1330 &'error'&: There is some error in the router (for example, a syntax error in
1331 its configuration). The action is as for defer.
1334 If an address reaches the end of the routers without having been accepted by
1335 any of them, it is bounced as unrouteable. The default error message in this
1336 situation is &"unrouteable address"&, but you can set your own message by
1337 making use of the &%cannot_route_message%& option. This can be set for any
1338 router; the value from the last router that &"saw"& the address is used.
1340 Sometimes while routing you want to fail a delivery when some conditions are
1341 met but others are not, instead of passing the address on for further routing.
1342 You can do this by having a second router that explicitly fails the delivery
1343 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1344 facility for this purpose.
1347 .section "Duplicate addresses" "SECID17"
1348 .cindex "case of local parts"
1349 .cindex "address duplicate, discarding"
1350 .cindex "duplicate addresses"
1351 Once routing is complete, Exim scans the addresses that are assigned to local
1352 and remote transports, and discards any duplicates that it finds. During this
1353 check, local parts are treated as case-sensitive. This happens only when
1354 actually delivering a message; when testing routers with &%-bt%&, all the
1355 routed addresses are shown.
1359 .section "Router preconditions" "SECTrouprecon"
1360 .cindex "router" "preconditions, order of processing"
1361 .cindex "preconditions" "order of processing"
1362 The preconditions that are tested for each router are listed below, in the
1363 order in which they are tested. The individual configuration options are
1364 described in more detail in chapter &<<CHAProutergeneric>>&.
1367 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1368 the local parts handled by the router may or must have certain prefixes and/or
1369 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1370 skipped. These conditions are tested first. When an affix is present, it is
1371 removed from the local part before further processing, including the evaluation
1372 of any other conditions.
1374 Routers can be designated for use only when not verifying an address, that is,
1375 only when routing it for delivery (or testing its delivery routing). If the
1376 &%verify%& option is set false, the router is skipped when Exim is verifying an
1378 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1379 &%verify_recipient%&, which independently control the use of the router for
1380 sender and recipient verification. You can set these options directly if
1381 you want a router to be used for only one type of verification.
1382 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1384 If the &%address_test%& option is set false, the router is skipped when Exim is
1385 run with the &%-bt%& option to test an address routing. This can be helpful
1386 when the first router sends all new messages to a scanner of some sort; it
1387 makes it possible to use &%-bt%& to test subsequent delivery routing without
1388 having to simulate the effect of the scanner.
1390 Routers can be designated for use only when verifying an address, as
1391 opposed to routing it for delivery. The &%verify_only%& option controls this.
1392 Again, cutthrough delivery counts as a verification.
1394 Individual routers can be explicitly skipped when running the routers to
1395 check an address given in the SMTP EXPN command (see the &%expn%& option).
1397 If the &%domains%& option is set, the domain of the address must be in the set
1398 of domains that it defines.
1400 .vindex "&$local_part_prefix$&"
1401 .vindex "&$local_part$&"
1402 .vindex "&$local_part_suffix$&"
1403 If the &%local_parts%& option is set, the local part of the address must be in
1404 the set of local parts that it defines. If &%local_part_prefix%& or
1405 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1406 part before this check. If you want to do precondition tests on local parts
1407 that include affixes, you can do so by using a &%condition%& option (see below)
1408 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1409 &$local_part_suffix$& as necessary.
1411 .vindex "&$local_user_uid$&"
1412 .vindex "&$local_user_gid$&"
1414 If the &%check_local_user%& option is set, the local part must be the name of
1415 an account on the local host. If this check succeeds, the uid and gid of the
1416 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1417 user's home directory is placed in &$home$&; these values can be used in the
1418 remaining preconditions.
1420 If the &%router_home_directory%& option is set, it is expanded at this point,
1421 because it overrides the value of &$home$&. If this expansion were left till
1422 later, the value of &$home$& as set by &%check_local_user%& would be used in
1423 subsequent tests. Having two different values of &$home$& in the same router
1424 could lead to confusion.
1426 If the &%senders%& option is set, the envelope sender address must be in the
1427 set of addresses that it defines.
1429 If the &%require_files%& option is set, the existence or non-existence of
1430 specified files is tested.
1432 .cindex "customizing" "precondition"
1433 If the &%condition%& option is set, it is evaluated and tested. This option
1434 uses an expanded string to allow you to set up your own custom preconditions.
1435 Expanded strings are described in chapter &<<CHAPexpand>>&.
1439 Note that &%require_files%& comes near the end of the list, so you cannot use
1440 it to check for the existence of a file in which to lookup up a domain, local
1441 part, or sender. However, as these options are all expanded, you can use the
1442 &%exists%& expansion condition to make such tests within each condition. The
1443 &%require_files%& option is intended for checking files that the router may be
1444 going to use internally, or which are needed by a specific transport (for
1445 example, &_.procmailrc_&).
1449 .section "Delivery in detail" "SECID18"
1450 .cindex "delivery" "in detail"
1451 When a message is to be delivered, the sequence of events is as follows:
1454 If a system-wide filter file is specified, the message is passed to it. The
1455 filter may add recipients to the message, replace the recipients, discard the
1456 message, cause a new message to be generated, or cause the message delivery to
1457 fail. The format of the system filter file is the same as for Exim user filter
1458 files, described in the separate document entitled &'Exim's interfaces to mail
1460 .cindex "Sieve filter" "not available for system filter"
1461 (&*Note*&: Sieve cannot be used for system filter files.)
1463 Some additional features are available in system filters &-- see chapter
1464 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1465 filter only once per delivery attempt, however many recipients it has. However,
1466 if there are several delivery attempts because one or more addresses could not
1467 be immediately delivered, the system filter is run each time. The filter
1468 condition &%first_delivery%& can be used to detect the first run of the system
1471 Each recipient address is offered to each configured router in turn, subject to
1472 its preconditions, until one is able to handle it. If no router can handle the
1473 address, that is, if they all decline, the address is failed. Because routers
1474 can be targeted at particular domains, several locally handled domains can be
1475 processed entirely independently of each other.
1477 .cindex "routing" "loops in"
1478 .cindex "loop" "while routing"
1479 A router that accepts an address may assign it to a local or a remote
1480 transport. However, the transport is not run at this time. Instead, the address
1481 is placed on a list for the particular transport, which will be run later.
1482 Alternatively, the router may generate one or more new addresses (typically
1483 from alias, forward, or filter files). New addresses are fed back into this
1484 process from the top, but in order to avoid loops, a router ignores any address
1485 which has an identically-named ancestor that was processed by itself.
1487 When all the routing has been done, addresses that have been successfully
1488 handled are passed to their assigned transports. When local transports are
1489 doing real local deliveries, they handle only one address at a time, but if a
1490 local transport is being used as a pseudo-remote transport (for example, to
1491 collect batched SMTP messages for transmission by some other means) multiple
1492 addresses can be handled. Remote transports can always handle more than one
1493 address at a time, but can be configured not to do so, or to restrict multiple
1494 addresses to the same domain.
1496 Each local delivery to a file or a pipe runs in a separate process under a
1497 non-privileged uid, and these deliveries are run one at a time. Remote
1498 deliveries also run in separate processes, normally under a uid that is private
1499 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1500 run in parallel. The maximum number of simultaneous remote deliveries for any
1501 one message is set by the &%remote_max_parallel%& option.
1502 The order in which deliveries are done is not defined, except that all local
1503 deliveries happen before any remote deliveries.
1505 .cindex "queue runner"
1506 When it encounters a local delivery during a queue run, Exim checks its retry
1507 database to see if there has been a previous temporary delivery failure for the
1508 address before running the local transport. If there was a previous failure,
1509 Exim does not attempt a new delivery until the retry time for the address is
1510 reached. However, this happens only for delivery attempts that are part of a
1511 queue run. Local deliveries are always attempted when delivery immediately
1512 follows message reception, even if retry times are set for them. This makes for
1513 better behaviour if one particular message is causing problems (for example,
1514 causing quota overflow, or provoking an error in a filter file).
1516 .cindex "delivery" "retry in remote transports"
1517 Remote transports do their own retry handling, since an address may be
1518 deliverable to one of a number of hosts, each of which may have a different
1519 retry time. If there have been previous temporary failures and no host has
1520 reached its retry time, no delivery is attempted, whether in a queue run or
1521 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1523 If there were any permanent errors, a bounce message is returned to an
1524 appropriate address (the sender in the common case), with details of the error
1525 for each failing address. Exim can be configured to send copies of bounce
1526 messages to other addresses.
1528 .cindex "delivery" "deferral"
1529 If one or more addresses suffered a temporary failure, the message is left on
1530 the queue, to be tried again later. Delivery of these addresses is said to be
1533 When all the recipient addresses have either been delivered or bounced,
1534 handling of the message is complete. The spool files and message log are
1535 deleted, though the message log can optionally be preserved if required.
1541 .section "Retry mechanism" "SECID19"
1542 .cindex "delivery" "retry mechanism"
1543 .cindex "retry" "description of mechanism"
1544 .cindex "queue runner"
1545 Exim's mechanism for retrying messages that fail to get delivered at the first
1546 attempt is the queue runner process. You must either run an Exim daemon that
1547 uses the &%-q%& option with a time interval to start queue runners at regular
1548 intervals, or use some other means (such as &'cron'&) to start them. If you do
1549 not arrange for queue runners to be run, messages that fail temporarily at the
1550 first attempt will remain on your queue for ever. A queue runner process works
1551 its way through the queue, one message at a time, trying each delivery that has
1552 passed its retry time.
1553 You can run several queue runners at once.
1555 Exim uses a set of configured rules to determine when next to retry the failing
1556 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1557 should give up trying to deliver to the address, at which point it generates a
1558 bounce message. If no retry rules are set for a particular host, address, and
1559 error combination, no retries are attempted, and temporary errors are treated
1564 .section "Temporary delivery failure" "SECID20"
1565 .cindex "delivery" "temporary failure"
1566 There are many reasons why a message may not be immediately deliverable to a
1567 particular address. Failure to connect to a remote machine (because it, or the
1568 connection to it, is down) is one of the most common. Temporary failures may be
1569 detected during routing as well as during the transport stage of delivery.
1570 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1571 is on a file system where the user is over quota. Exim can be configured to
1572 impose its own quotas on local mailboxes; where system quotas are set they will
1575 If a host is unreachable for a period of time, a number of messages may be
1576 waiting for it by the time it recovers, and sending them in a single SMTP
1577 connection is clearly beneficial. Whenever a delivery to a remote host is
1579 .cindex "hints database" "deferred deliveries"
1580 Exim makes a note in its hints database, and whenever a successful
1581 SMTP delivery has happened, it looks to see if any other messages are waiting
1582 for the same host. If any are found, they are sent over the same SMTP
1583 connection, subject to a configuration limit as to the maximum number in any
1588 .section "Permanent delivery failure" "SECID21"
1589 .cindex "delivery" "permanent failure"
1590 .cindex "bounce message" "when generated"
1591 When a message cannot be delivered to some or all of its intended recipients, a
1592 bounce message is generated. Temporary delivery failures turn into permanent
1593 errors when their timeout expires. All the addresses that fail in a given
1594 delivery attempt are listed in a single message. If the original message has
1595 many recipients, it is possible for some addresses to fail in one delivery
1596 attempt and others to fail subsequently, giving rise to more than one bounce
1597 message. The wording of bounce messages can be customized by the administrator.
1598 See chapter &<<CHAPemsgcust>>& for details.
1600 .cindex "&'X-Failed-Recipients:'& header line"
1601 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1602 failed addresses, for the benefit of programs that try to analyse such messages
1605 .cindex "bounce message" "recipient of"
1606 A bounce message is normally sent to the sender of the original message, as
1607 obtained from the message's envelope. For incoming SMTP messages, this is the
1608 address given in the MAIL command. However, when an address is expanded via a
1609 forward or alias file, an alternative address can be specified for delivery
1610 failures of the generated addresses. For a mailing list expansion (see section
1611 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1616 .section "Failures to deliver bounce messages" "SECID22"
1617 .cindex "bounce message" "failure to deliver"
1618 If a bounce message (either locally generated or received from a remote host)
1619 itself suffers a permanent delivery failure, the message is left on the queue,
1620 but it is frozen, awaiting the attention of an administrator. There are options
1621 that can be used to make Exim discard such failed messages, or to keep them
1622 for only a short time (see &%timeout_frozen_after%& and
1623 &%ignore_bounce_errors_after%&).
1629 . ////////////////////////////////////////////////////////////////////////////
1630 . ////////////////////////////////////////////////////////////////////////////
1632 .chapter "Building and installing Exim" "CHID3"
1633 .scindex IIDbuex "building Exim"
1635 .section "Unpacking" "SECID23"
1636 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1637 creates a directory with the name of the current release (for example,
1638 &_exim-&version()_&) into which the following files are placed:
1641 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1642 .irow &_CHANGES_& "contains a reference to where changes are &&&
1644 .irow &_LICENCE_& "the GNU General Public Licence"
1645 .irow &_Makefile_& "top-level make file"
1646 .irow &_NOTICE_& "conditions for the use of Exim"
1647 .irow &_README_& "list of files, directories and simple build &&&
1651 Other files whose names begin with &_README_& may also be present. The
1652 following subdirectories are created:
1655 .irow &_Local_& "an empty directory for local configuration files"
1656 .irow &_OS_& "OS-specific files"
1657 .irow &_doc_& "documentation files"
1658 .irow &_exim_monitor_& "source files for the Exim monitor"
1659 .irow &_scripts_& "scripts used in the build process"
1660 .irow &_src_& "remaining source files"
1661 .irow &_util_& "independent utilities"
1664 The main utility programs are contained in the &_src_& directory, and are built
1665 with the Exim binary. The &_util_& directory contains a few optional scripts
1666 that may be useful to some sites.
1669 .section "Multiple machine architectures and operating systems" "SECID24"
1670 .cindex "building Exim" "multiple OS/architectures"
1671 The building process for Exim is arranged to make it easy to build binaries for
1672 a number of different architectures and operating systems from the same set of
1673 source files. Compilation does not take place in the &_src_& directory.
1674 Instead, a &'build directory'& is created for each architecture and operating
1676 .cindex "symbolic link" "to build directory"
1677 Symbolic links to the sources are installed in this directory, which is where
1678 the actual building takes place. In most cases, Exim can discover the machine
1679 architecture and operating system for itself, but the defaults can be
1680 overridden if necessary.
1683 .section "PCRE library" "SECTpcre"
1684 .cindex "PCRE library"
1685 Exim no longer has an embedded PCRE library as the vast majority of
1686 modern systems include PCRE as a system library, although you may need
1687 to install the PCRE or PCRE development package for your operating
1688 system. If your system has a normal PCRE installation the Exim build
1689 process will need no further configuration. If the library or the
1690 headers are in an unusual location you will need to either set the PCRE_LIBS
1691 and INCLUDE directives appropriately,
1692 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1693 If your operating system has no
1694 PCRE support then you will need to obtain and build the current PCRE
1695 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1696 More information on PCRE is available at &url(http://www.pcre.org/).
1698 .section "DBM libraries" "SECTdb"
1699 .cindex "DBM libraries" "discussion of"
1700 .cindex "hints database" "DBM files used for"
1701 Even if you do not use any DBM files in your configuration, Exim still needs a
1702 DBM library in order to operate, because it uses indexed files for its hints
1703 databases. Unfortunately, there are a number of DBM libraries in existence, and
1704 different operating systems often have different ones installed.
1706 .cindex "Solaris" "DBM library for"
1707 .cindex "IRIX, DBM library for"
1708 .cindex "BSD, DBM library for"
1709 .cindex "Linux, DBM library for"
1710 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1711 Linux distribution, the DBM configuration should happen automatically, and you
1712 may be able to ignore this section. Otherwise, you may have to learn more than
1713 you would like about DBM libraries from what follows.
1715 .cindex "&'ndbm'& DBM library"
1716 Licensed versions of Unix normally contain a library of DBM functions operating
1717 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1718 versions of Unix seem to vary in what they contain as standard. In particular,
1719 some early versions of Linux have no default DBM library, and different
1720 distributors have chosen to bundle different libraries with their packaged
1721 versions. However, the more recent releases seem to have standardized on the
1722 Berkeley DB library.
1724 Different DBM libraries have different conventions for naming the files they
1725 use. When a program opens a file called &_dbmfile_&, there are several
1729 A traditional &'ndbm'& implementation, such as that supplied as part of
1730 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1732 .cindex "&'gdbm'& DBM library"
1733 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1734 compatibility interface it makes two different hard links to it with names
1735 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1736 file name is used unmodified.
1738 .cindex "Berkeley DB library"
1739 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1740 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1741 programmer exactly the same as the traditional &'ndbm'& implementation.
1743 If the Berkeley package is used in its native mode, it operates on a single
1744 file called &_dbmfile_&; the programmer's interface is somewhat different to
1745 the traditional &'ndbm'& interface.
1747 To complicate things further, there are several very different versions of the
1748 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1749 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1750 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1751 versions of Berkeley DB can be obtained from
1752 &url(http://www.sleepycat.com/).
1754 .cindex "&'tdb'& DBM library"
1755 Yet another DBM library, called &'tdb'&, is available from
1756 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1757 operates on a single file.
1761 .cindex "DBM libraries" "configuration for building"
1762 Exim and its utilities can be compiled to use any of these interfaces. In order
1763 to use any version of the Berkeley DB package in native mode, you must set
1764 USE_DB in an appropriate configuration file (typically
1765 &_Local/Makefile_&). For example:
1769 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1770 error is diagnosed if you set more than one of these.
1772 At the lowest level, the build-time configuration sets none of these options,
1773 thereby assuming an interface of type (1). However, some operating system
1774 configuration files (for example, those for the BSD operating systems and
1775 Linux) assume type (4) by setting USE_DB as their default, and the
1776 configuration files for Cygwin set USE_GDBM. Anything you set in
1777 &_Local/Makefile_&, however, overrides these system defaults.
1779 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1780 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1781 in one of these lines:
1786 Settings like that will work if the DBM library is installed in the standard
1787 place. Sometimes it is not, and the library's header file may also not be in
1788 the default path. You may need to set INCLUDE to specify where the header
1789 file is, and to specify the path to the library more fully in DBMLIB, as in
1792 INCLUDE=-I/usr/local/include/db-4.1
1793 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1795 There is further detailed discussion about the various DBM libraries in the
1796 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1800 .section "Pre-building configuration" "SECID25"
1801 .cindex "building Exim" "pre-building configuration"
1802 .cindex "configuration for building Exim"
1803 .cindex "&_Local/Makefile_&"
1804 .cindex "&_src/EDITME_&"
1805 Before building Exim, a local configuration file that specifies options
1806 independent of any operating system has to be created with the name
1807 &_Local/Makefile_&. A template for this file is supplied as the file
1808 &_src/EDITME_&, and it contains full descriptions of all the option settings
1809 therein. These descriptions are therefore not repeated here. If you are
1810 building Exim for the first time, the simplest thing to do is to copy
1811 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1813 There are three settings that you must supply, because Exim will not build
1814 without them. They are the location of the run time configuration file
1815 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1816 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1817 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1818 a colon-separated list of file names; Exim uses the first of them that exists.
1820 There are a few other parameters that can be specified either at build time or
1821 at run time, to enable the same binary to be used on a number of different
1822 machines. However, if the locations of Exim's spool directory and log file
1823 directory (if not within the spool directory) are fixed, it is recommended that
1824 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1825 detected early in Exim's execution (such as a malformed configuration file) can
1828 .cindex "content scanning" "specifying at build time"
1829 Exim's interfaces for calling virus and spam scanning software directly from
1830 access control lists are not compiled by default. If you want to include these
1831 facilities, you need to set
1833 WITH_CONTENT_SCAN=yes
1835 in your &_Local/Makefile_&. For details of the facilities themselves, see
1836 chapter &<<CHAPexiscan>>&.
1839 .cindex "&_Local/eximon.conf_&"
1840 .cindex "&_exim_monitor/EDITME_&"
1841 If you are going to build the Exim monitor, a similar configuration process is
1842 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1843 your installation and saved under the name &_Local/eximon.conf_&. If you are
1844 happy with the default settings described in &_exim_monitor/EDITME_&,
1845 &_Local/eximon.conf_& can be empty, but it must exist.
1847 This is all the configuration that is needed in straightforward cases for known
1848 operating systems. However, the building process is set up so that it is easy
1849 to override options that are set by default or by operating-system-specific
1850 configuration files, for example to change the name of the C compiler, which
1851 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1856 .section "Support for iconv()" "SECID26"
1857 .cindex "&[iconv()]& support"
1859 The contents of header lines in messages may be encoded according to the rules
1860 described RFC 2047. This makes it possible to transmit characters that are not
1861 in the ASCII character set, and to label them as being in a particular
1862 character set. When Exim is inspecting header lines by means of the &%$h_%&
1863 mechanism, it decodes them, and translates them into a specified character set
1864 (default is set at build time). The translation is possible only if the operating system
1865 supports the &[iconv()]& function.
1867 However, some of the operating systems that supply &[iconv()]& do not support
1868 very many conversions. The GNU &%libiconv%& library (available from
1869 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1870 systems to remedy this deficiency, as well as on systems that do not supply
1871 &[iconv()]& at all. After installing &%libiconv%&, you should add
1875 to your &_Local/Makefile_& and rebuild Exim.
1879 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1880 .cindex "TLS" "including support for TLS"
1881 .cindex "encryption" "including support for"
1882 .cindex "SUPPORT_TLS"
1883 .cindex "OpenSSL" "building Exim with"
1884 .cindex "GnuTLS" "building Exim with"
1885 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1886 command as per RFC 2487. It can also support legacy clients that expect to
1887 start a TLS session immediately on connection to a non-standard port (see the
1888 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1891 If you want to build Exim with TLS support, you must first install either the
1892 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1895 If OpenSSL is installed, you should set
1898 TLS_LIBS=-lssl -lcrypto
1900 in &_Local/Makefile_&. You may also need to specify the locations of the
1901 OpenSSL library and include files. For example:
1904 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1905 TLS_INCLUDE=-I/usr/local/openssl/include/
1907 .cindex "pkg-config" "OpenSSL"
1908 If you have &'pkg-config'& available, then instead you can just use:
1911 USE_OPENSSL_PC=openssl
1913 .cindex "USE_GNUTLS"
1914 If GnuTLS is installed, you should set
1918 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1920 in &_Local/Makefile_&, and again you may need to specify the locations of the
1921 library and include files. For example:
1925 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1926 TLS_INCLUDE=-I/usr/gnu/include
1928 .cindex "pkg-config" "GnuTLS"
1929 If you have &'pkg-config'& available, then instead you can just use:
1933 USE_GNUTLS_PC=gnutls
1936 You do not need to set TLS_INCLUDE if the relevant directory is already
1937 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1938 given in chapter &<<CHAPTLS>>&.
1943 .section "Use of tcpwrappers" "SECID27"
1945 .cindex "tcpwrappers, building Exim to support"
1946 .cindex "USE_TCP_WRAPPERS"
1947 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1948 .cindex "tcp_wrappers_daemon_name"
1949 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1950 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1951 alternative to Exim's own checking facilities for installations that are
1952 already making use of &'tcpwrappers'& for other purposes. To do this, you
1953 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1954 &_tcpd.h_& to be available at compile time, and also ensure that the library
1955 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1956 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1959 USE_TCP_WRAPPERS=yes
1960 CFLAGS=-O -I/usr/local/include
1961 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1963 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1964 files is &"exim"&. For example, the line
1966 exim : LOCAL 192.168.1. .friendly.domain.example
1968 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1969 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1970 All other connections are denied. The daemon name used by &'tcpwrappers'&
1971 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1972 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1973 configure file. Consult the &'tcpwrappers'& documentation for
1977 .section "Including support for IPv6" "SECID28"
1978 .cindex "IPv6" "including support for"
1979 Exim contains code for use on systems that have IPv6 support. Setting
1980 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1981 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1982 where the IPv6 support is not fully integrated into the normal include and
1985 Two different types of DNS record for handling IPv6 addresses have been
1986 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1987 currently seen as the mainstream. Another record type called A6 was proposed
1988 as better than AAAA because it had more flexibility. However, it was felt to be
1989 over-complex, and its status was reduced to &"experimental"&.
1991 have a compile option for including A6 record support but this has now been
1996 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
1997 .cindex "lookup modules"
1998 .cindex "dynamic modules"
1999 .cindex ".so building"
2000 On some platforms, Exim supports not compiling all lookup types directly into
2001 the main binary, instead putting some into external modules which can be loaded
2003 This permits packagers to build Exim with support for lookups with extensive
2004 library dependencies without requiring all users to install all of those
2006 Most, but not all, lookup types can be built this way.
2008 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2009 installed; Exim will only load modules from that directory, as a security
2010 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2011 for your OS; see &_OS/Makefile-Linux_& for an example.
2012 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2013 see &_src/EDITME_& for details.
2015 Then, for each module to be loaded dynamically, define the relevant
2016 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2017 For example, this will build in lsearch but load sqlite and mysql support
2026 .section "The building process" "SECID29"
2027 .cindex "build directory"
2028 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2029 created, run &'make'& at the top level. It determines the architecture and
2030 operating system types, and creates a build directory if one does not exist.
2031 For example, on a Sun system running Solaris 8, the directory
2032 &_build-SunOS5-5.8-sparc_& is created.
2033 .cindex "symbolic link" "to source files"
2034 Symbolic links to relevant source files are installed in the build directory.
2036 If this is the first time &'make'& has been run, it calls a script that builds
2037 a make file inside the build directory, using the configuration files from the
2038 &_Local_& directory. The new make file is then passed to another instance of
2039 &'make'&. This does the real work, building a number of utility scripts, and
2040 then compiling and linking the binaries for the Exim monitor (if configured), a
2041 number of utility programs, and finally Exim itself. The command &`make
2042 makefile`& can be used to force a rebuild of the make file in the build
2043 directory, should this ever be necessary.
2045 If you have problems building Exim, check for any comments there may be in the
2046 &_README_& file concerning your operating system, and also take a look at the
2047 FAQ, where some common problems are covered.
2051 .section 'Output from &"make"&' "SECID283"
2052 The output produced by the &'make'& process for compile lines is often very
2053 unreadable, because these lines can be very long. For this reason, the normal
2054 output is suppressed by default, and instead output similar to that which
2055 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2056 each module that is being compiled or linked. However, it is still possible to
2057 get the full output, by calling &'make'& like this:
2061 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2062 command reflection in &'make'&. When you ask for the full output, it is
2063 given in addition to the short output.
2067 .section "Overriding build-time options for Exim" "SECToverride"
2068 .cindex "build-time options, overriding"
2069 The main make file that is created at the beginning of the building process
2070 consists of the concatenation of a number of files which set configuration
2071 values, followed by a fixed set of &'make'& instructions. If a value is set
2072 more than once, the last setting overrides any previous ones. This provides a
2073 convenient way of overriding defaults. The files that are concatenated are, in
2076 &_OS/Makefile-Default_&
2077 &_OS/Makefile-_&<&'ostype'&>
2079 &_Local/Makefile-_&<&'ostype'&>
2080 &_Local/Makefile-_&<&'archtype'&>
2081 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2082 &_OS/Makefile-Base_&
2084 .cindex "&_Local/Makefile_&"
2085 .cindex "building Exim" "operating system type"
2086 .cindex "building Exim" "architecture type"
2087 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2088 architecture type. &_Local/Makefile_& is required to exist, and the building
2089 process fails if it is absent. The other three &_Local_& files are optional,
2090 and are often not needed.
2092 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2093 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2094 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2095 values are used, thereby providing a means of forcing particular settings.
2096 Otherwise, the scripts try to get values from the &%uname%& command. If this
2097 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2098 of &'ad hoc'& transformations are then applied, to produce the standard names
2099 that Exim expects. You can run these scripts directly from the shell in order
2100 to find out what values are being used on your system.
2103 &_OS/Makefile-Default_& contains comments about the variables that are set
2104 therein. Some (but not all) are mentioned below. If there is something that
2105 needs changing, review the contents of this file and the contents of the make
2106 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2110 .cindex "building Exim" "overriding default settings"
2111 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2112 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2113 need to change the original files. Instead, you should make the changes by
2114 putting the new values in an appropriate &_Local_& file. For example,
2115 .cindex "Tru64-Unix build-time settings"
2116 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2117 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2118 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2119 called with the option &%-std1%&, to make it recognize some of the features of
2120 Standard C that Exim uses. (Most other compilers recognize Standard C by
2121 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2122 containing the lines
2127 If you are compiling for just one operating system, it may be easier to put
2128 these lines directly into &_Local/Makefile_&.
2130 Keeping all your local configuration settings separate from the distributed
2131 files makes it easy to transfer them to new versions of Exim simply by copying
2132 the contents of the &_Local_& directory.
2135 .cindex "NIS lookup type" "including support for"
2136 .cindex "NIS+ lookup type" "including support for"
2137 .cindex "LDAP" "including support for"
2138 .cindex "lookup" "inclusion in binary"
2139 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2140 lookup, but not all systems have these components installed, so the default is
2141 not to include the relevant code in the binary. All the different kinds of file
2142 and database lookup that Exim supports are implemented as separate code modules
2143 which are included only if the relevant compile-time options are set. In the
2144 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2150 and similar settings apply to the other lookup types. They are all listed in
2151 &_src/EDITME_&. In many cases the relevant include files and interface
2152 libraries need to be installed before compiling Exim.
2153 .cindex "cdb" "including support for"
2154 However, there are some optional lookup types (such as cdb) for which
2155 the code is entirely contained within Exim, and no external include
2156 files or libraries are required. When a lookup type is not included in the
2157 binary, attempts to configure Exim to use it cause run time configuration
2160 .cindex "pkg-config" "lookups"
2161 .cindex "pkg-config" "authenticators"
2162 Many systems now use a tool called &'pkg-config'& to encapsulate information
2163 about how to compile against a library; Exim has some initial support for
2164 being able to use pkg-config for lookups and authenticators. For any given
2165 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2166 variable with the &`_PC`& suffix in the name and assign as the value the
2167 name of the package to be queried. The results of querying via the
2168 &'pkg-config'& command will be added to the appropriate Makefile variables
2169 with &`+=`& directives, so your version of &'make'& will need to support that
2170 syntax. For instance:
2173 LOOKUP_SQLITE_PC=sqlite3
2175 AUTH_GSASL_PC=libgsasl
2176 AUTH_HEIMDAL_GSSAPI=yes
2177 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2180 .cindex "Perl" "including support for"
2181 Exim can be linked with an embedded Perl interpreter, allowing Perl
2182 subroutines to be called during string expansion. To enable this facility,
2186 must be defined in &_Local/Makefile_&. Details of this facility are given in
2187 chapter &<<CHAPperl>>&.
2189 .cindex "X11 libraries, location of"
2190 The location of the X11 libraries is something that varies a lot between
2191 operating systems, and there may be different versions of X11 to cope
2192 with. Exim itself makes no use of X11, but if you are compiling the Exim
2193 monitor, the X11 libraries must be available.
2194 The following three variables are set in &_OS/Makefile-Default_&:
2197 XINCLUDE=-I$(X11)/include
2198 XLFLAGS=-L$(X11)/lib
2200 These are overridden in some of the operating-system configuration files. For
2201 example, in &_OS/Makefile-SunOS5_& there is
2204 XINCLUDE=-I$(X11)/include
2205 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2207 If you need to override the default setting for your operating system, place a
2208 definition of all three of these variables into your
2209 &_Local/Makefile-<ostype>_& file.
2212 If you need to add any extra libraries to the link steps, these can be put in a
2213 variable called EXTRALIBS, which appears in all the link commands, but by
2214 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2215 command for linking the main Exim binary, and not for any associated utilities.
2217 .cindex "DBM libraries" "configuration for building"
2218 There is also DBMLIB, which appears in the link commands for binaries that
2219 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2220 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2221 binary, and which can be used, for example, to include additional X11
2224 .cindex "configuration file" "editing"
2225 The make file copes with rebuilding Exim correctly if any of the configuration
2226 files are edited. However, if an optional configuration file is deleted, it is
2227 necessary to touch the associated non-optional file (that is,
2228 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2231 .section "OS-specific header files" "SECID30"
2233 .cindex "building Exim" "OS-specific C header files"
2234 The &_OS_& directory contains a number of files with names of the form
2235 &_os.h-<ostype>_&. These are system-specific C header files that should not
2236 normally need to be changed. There is a list of macro settings that are
2237 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2238 are porting Exim to a new operating system.
2242 .section "Overriding build-time options for the monitor" "SECID31"
2243 .cindex "building Eximon"
2244 A similar process is used for overriding things when building the Exim monitor,
2245 where the files that are involved are
2247 &_OS/eximon.conf-Default_&
2248 &_OS/eximon.conf-_&<&'ostype'&>
2249 &_Local/eximon.conf_&
2250 &_Local/eximon.conf-_&<&'ostype'&>
2251 &_Local/eximon.conf-_&<&'archtype'&>
2252 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2254 .cindex "&_Local/eximon.conf_&"
2255 As with Exim itself, the final three files need not exist, and in this case the
2256 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2257 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2258 variables of the same name, preceded by EXIMON_. For example, setting
2259 EXIMON_LOG_DEPTH in the environment overrides the value of
2260 LOG_DEPTH at run time.
2264 .section "Installing Exim binaries and scripts" "SECID32"
2265 .cindex "installing Exim"
2266 .cindex "BIN_DIRECTORY"
2267 The command &`make install`& runs the &(exim_install)& script with no
2268 arguments. The script copies binaries and utility scripts into the directory
2269 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2270 .cindex "setuid" "installing Exim with"
2271 The install script copies files only if they are newer than the files they are
2272 going to replace. The Exim binary is required to be owned by root and have the
2273 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2274 install`& as root so that it can set up the Exim binary in this way. However, in
2275 some special situations (for example, if a host is doing no local deliveries)
2276 it may be possible to run Exim without making the binary setuid root (see
2277 chapter &<<CHAPsecurity>>& for details).
2279 .cindex "CONFIGURE_FILE"
2280 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2281 in &_Local/Makefile_&. If this names a single file, and the file does not
2282 exist, the default configuration file &_src/configure.default_& is copied there
2283 by the installation script. If a run time configuration file already exists, it
2284 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2285 alternative files, no default is installed.
2287 .cindex "system aliases file"
2288 .cindex "&_/etc/aliases_&"
2289 One change is made to the default configuration file when it is installed: the
2290 default configuration contains a router that references a system aliases file.
2291 The path to this file is set to the value specified by
2292 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2293 If the system aliases file does not exist, the installation script creates it,
2294 and outputs a comment to the user.
2296 The created file contains no aliases, but it does contain comments about the
2297 aliases a site should normally have. Mail aliases have traditionally been
2298 kept in &_/etc/aliases_&. However, some operating systems are now using
2299 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2300 Exim's configuration if necessary.
2302 The default configuration uses the local host's name as the only local domain,
2303 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2304 running as the local user. System aliases and &_.forward_& files in users' home
2305 directories are supported, but no NIS or NIS+ support is configured. Domains
2306 other than the name of the local host are routed using the DNS, with delivery
2309 It is possible to install Exim for special purposes (such as building a binary
2310 distribution) in a private part of the file system. You can do this by a
2313 make DESTDIR=/some/directory/ install
2315 This has the effect of pre-pending the specified directory to all the file
2316 paths, except the name of the system aliases file that appears in the default
2317 configuration. (If a default alias file is created, its name &'is'& modified.)
2318 For backwards compatibility, ROOT is used if DESTDIR is not set,
2319 but this usage is deprecated.
2321 .cindex "installing Exim" "what is not installed"
2322 Running &'make install'& does not copy the Exim 4 conversion script
2323 &'convert4r4'&. You will probably run this only once if you are
2324 upgrading from Exim 3. None of the documentation files in the &_doc_&
2325 directory are copied, except for the info files when you have set
2326 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2328 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2329 to their names. The Exim binary itself, however, is handled differently. It is
2330 installed under a name that includes the version number and the compile number,
2331 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2332 called &_exim_& to point to the binary. If you are updating a previous version
2333 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2334 from the directory (as seen by other processes).
2336 .cindex "installing Exim" "testing the script"
2337 If you want to see what the &'make install'& will do before running it for
2338 real, you can pass the &%-n%& option to the installation script by this
2341 make INSTALL_ARG=-n install
2343 The contents of the variable INSTALL_ARG are passed to the installation
2344 script. You do not need to be root to run this test. Alternatively, you can run
2345 the installation script directly, but this must be from within the build
2346 directory. For example, from the top-level Exim directory you could use this
2349 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2351 .cindex "installing Exim" "install script options"
2352 There are two other options that can be supplied to the installation script.
2355 &%-no_chown%& bypasses the call to change the owner of the installed binary
2356 to root, and the call to make it a setuid binary.
2358 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2362 INSTALL_ARG can be used to pass these options to the script. For example:
2364 make INSTALL_ARG=-no_symlink install
2366 The installation script can also be given arguments specifying which files are
2367 to be copied. For example, to install just the Exim binary, and nothing else,
2368 without creating the symbolic link, you could use:
2370 make INSTALL_ARG='-no_symlink exim' install
2375 .section "Installing info documentation" "SECTinsinfdoc"
2376 .cindex "installing Exim" "&'info'& documentation"
2377 Not all systems use the GNU &'info'& system for documentation, and for this
2378 reason, the Texinfo source of Exim's documentation is not included in the main
2379 distribution. Instead it is available separately from the ftp site (see section
2382 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2383 source of the documentation is found in the source tree, running &`make
2384 install`& automatically builds the info files and installs them.
2388 .section "Setting up the spool directory" "SECID33"
2389 .cindex "spool directory" "creating"
2390 When it starts up, Exim tries to create its spool directory if it does not
2391 exist. The Exim uid and gid are used for the owner and group of the spool
2392 directory. Sub-directories are automatically created in the spool directory as
2398 .section "Testing" "SECID34"
2399 .cindex "testing" "installation"
2400 Having installed Exim, you can check that the run time configuration file is
2401 syntactically valid by running the following command, which assumes that the
2402 Exim binary directory is within your PATH environment variable:
2406 If there are any errors in the configuration file, Exim outputs error messages.
2407 Otherwise it outputs the version number and build date,
2408 the DBM library that is being used, and information about which drivers and
2409 other optional code modules are included in the binary.
2410 Some simple routing tests can be done by using the address testing option. For
2413 &`exim -bt`& <&'local username'&>
2415 should verify that it recognizes a local mailbox, and
2417 &`exim -bt`& <&'remote address'&>
2419 a remote one. Then try getting it to deliver mail, both locally and remotely.
2420 This can be done by passing messages directly to Exim, without going through a
2421 user agent. For example:
2423 exim -v postmaster@your.domain.example
2424 From: user@your.domain.example
2425 To: postmaster@your.domain.example
2426 Subject: Testing Exim
2428 This is a test message.
2431 The &%-v%& option causes Exim to output some verification of what it is doing.
2432 In this case you should see copies of three log lines, one for the message's
2433 arrival, one for its delivery, and one containing &"Completed"&.
2435 .cindex "delivery" "problems with"
2436 If you encounter problems, look at Exim's log files (&'mainlog'& and
2437 &'paniclog'&) to see if there is any relevant information there. Another source
2438 of information is running Exim with debugging turned on, by specifying the
2439 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2440 with debugging turned on by a command of the form
2442 &`exim -d -M`& <&'exim-message-id'&>
2444 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2445 produces rather a lot of output, but you can cut this down to specific areas.
2446 For example, if you use &%-d-all+route%& only the debugging information
2447 relevant to routing is included. (See the &%-d%& option in chapter
2448 &<<CHAPcommandline>>& for more details.)
2450 .cindex '&"sticky"& bit'
2451 .cindex "lock files"
2452 One specific problem that has shown up on some sites is the inability to do
2453 local deliveries into a shared mailbox directory, because it does not have the
2454 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2455 writing to a mailbox file, and if it cannot create the lock file, the delivery
2456 is deferred. You can get round this either by setting the &"sticky bit"& on the
2457 directory, or by setting a specific group for local deliveries and allowing
2458 that group to create files in the directory (see the comments above the
2459 &(local_delivery)& transport in the default configuration file). Another
2460 approach is to configure Exim not to use lock files, but just to rely on
2461 &[fcntl()]& locking instead. However, you should do this only if all user
2462 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2463 see chapter &<<CHAPappendfile>>&.
2465 One thing that cannot be tested on a system that is already running an MTA is
2466 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2467 &%-oX%& option can be used to run an Exim daemon that listens on some other
2468 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2469 &'exim_checkaccess'& utility can be used to check out policy controls on
2472 Testing a new version on a system that is already running Exim can most easily
2473 be done by building a binary with a different CONFIGURE_FILE setting. From
2474 within the run time configuration, all other file and directory names
2475 that Exim uses can be altered, in order to keep it entirely clear of the
2479 .section "Replacing another MTA with Exim" "SECID35"
2480 .cindex "replacing another MTA"
2481 Building and installing Exim for the first time does not of itself put it in
2482 general use. The name by which the system's MTA is called by mail user agents
2483 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2484 operating system), and it is necessary to make this name point to the &'exim'&
2485 binary in order to get the user agents to pass messages to Exim. This is
2486 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2487 or &_/usr/lib/sendmail_&
2488 .cindex "symbolic link" "to &'exim'& binary"
2489 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2490 privilege and executable status from the old MTA. It is then necessary to stop
2491 and restart the mailer daemon, if one is running.
2493 .cindex "FreeBSD, MTA indirection"
2494 .cindex "&_/etc/mail/mailer.conf_&"
2495 Some operating systems have introduced alternative ways of switching MTAs. For
2496 example, if you are running FreeBSD, you need to edit the file
2497 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2498 described. A typical example of the contents of this file for running Exim is
2501 sendmail /usr/exim/bin/exim
2502 send-mail /usr/exim/bin/exim
2503 mailq /usr/exim/bin/exim -bp
2504 newaliases /usr/bin/true
2506 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2507 your Exim installation is &"live"&. Check it by sending a message from your
2508 favourite user agent.
2510 You should consider what to tell your users about the change of MTA. Exim may
2511 have different capabilities to what was previously running, and there are
2512 various operational differences such as the text of messages produced by
2513 command line options and in bounce messages. If you allow your users to make
2514 use of Exim's filtering capabilities, you should make the document entitled
2515 &'Exim's interface to mail filtering'& available to them.
2519 .section "Upgrading Exim" "SECID36"
2520 .cindex "upgrading Exim"
2521 If you are already running Exim on your host, building and installing a new
2522 version automatically makes it available to MUAs, or any other programs that
2523 call the MTA directly. However, if you are running an Exim daemon, you do need
2524 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2525 new binary. You do not need to stop processing mail in order to install a new
2526 version of Exim. The install script does not modify an existing runtime
2532 .section "Stopping the Exim daemon on Solaris" "SECID37"
2533 .cindex "Solaris" "stopping Exim on"
2534 The standard command for stopping the mailer daemon on Solaris is
2536 /etc/init.d/sendmail stop
2538 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2539 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2540 for the text &"sendmail"&; this is not present because the actual program name
2541 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2542 solution is to replace the line that finds the process id with something like
2544 pid=`cat /var/spool/exim/exim-daemon.pid`
2546 to obtain the daemon's pid directly from the file that Exim saves it in.
2548 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2549 still be received from local processes, and if automatic delivery is configured
2550 (the normal case), deliveries will still occur.
2555 . ////////////////////////////////////////////////////////////////////////////
2556 . ////////////////////////////////////////////////////////////////////////////
2558 .chapter "The Exim command line" "CHAPcommandline"
2559 .scindex IIDclo1 "command line" "options"
2560 .scindex IIDclo2 "options" "command line"
2561 Exim's command line takes the standard Unix form of a sequence of options,
2562 each starting with a hyphen character, followed by a number of arguments. The
2563 options are compatible with the main options of Sendmail, and there are also
2564 some additional options, some of which are compatible with Smail 3. Certain
2565 combinations of options do not make sense, and provoke an error if used.
2566 The form of the arguments depends on which options are set.
2569 .section "Setting options by program name" "SECID38"
2571 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2572 were present before any other options.
2573 The &%-bp%& option requests a listing of the contents of the mail queue on the
2575 This feature is for compatibility with some systems that contain a command of
2576 that name in one of the standard libraries, symbolically linked to
2577 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2580 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2581 were present before any other options, for compatibility with Smail. The
2582 &%-bS%& option is used for reading in a number of messages in batched SMTP
2586 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2587 &%-oee%& options were present before any other options, for compatibility with
2588 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2591 .cindex "queue runner"
2592 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2593 were present before any other options, for compatibility with Smail. The &%-q%&
2594 option causes a single queue runner process to be started.
2596 .cindex "&'newaliases'&"
2597 .cindex "alias file" "building"
2598 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2599 If Exim is called under the name &'newaliases'& it behaves as if the option
2600 &%-bi%& were present before any other options, for compatibility with Sendmail.
2601 This option is used for rebuilding Sendmail's alias file. Exim does not have
2602 the concept of a single alias file, but can be configured to run a given
2603 command if called with the &%-bi%& option.
2606 .section "Trusted and admin users" "SECTtrustedadmin"
2607 Some Exim options are available only to &'trusted users'& and others are
2608 available only to &'admin users'&. In the description below, the phrases &"Exim
2609 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2610 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2611 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2614 .cindex "trusted users" "definition of"
2615 .cindex "user" "trusted definition of"
2616 The trusted users are root, the Exim user, any user listed in the
2617 &%trusted_users%& configuration option, and any user whose current group or any
2618 supplementary group is one of those listed in the &%trusted_groups%&
2619 configuration option. Note that the Exim group is not automatically trusted.
2621 .cindex '&"From"& line'
2622 .cindex "envelope sender"
2623 Trusted users are always permitted to use the &%-f%& option or a leading
2624 &"From&~"& line to specify the envelope sender of a message that is passed to
2625 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2626 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2627 users to set envelope senders.
2629 .cindex "&'From:'& header line"
2630 .cindex "&'Sender:'& header line"
2631 .cindex "header lines" "From:"
2632 .cindex "header lines" "Sender:"
2633 For a trusted user, there is never any check on the contents of the &'From:'&
2634 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2635 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2637 Trusted users may also specify a host name, host address, interface address,
2638 protocol name, ident value, and authentication data when submitting a message
2639 locally. Thus, they are able to insert messages into Exim's queue locally that
2640 have the characteristics of messages received from a remote host. Untrusted
2641 users may in some circumstances use &%-f%&, but can never set the other values
2642 that are available to trusted users.
2644 .cindex "user" "admin definition of"
2645 .cindex "admin user" "definition of"
2646 The admin users are root, the Exim user, and any user that is a member of the
2647 Exim group or of any group listed in the &%admin_groups%& configuration option.
2648 The current group does not have to be one of these groups.
2650 Admin users are permitted to list the queue, and to carry out certain
2651 operations on messages, for example, to force delivery failures. It is also
2652 necessary to be an admin user in order to see the full information provided by
2653 the Exim monitor, and full debugging output.
2655 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2656 Exim to attempt delivery of messages on its queue is restricted to admin users.
2657 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2658 option false (that is, specifying &%no_prod_requires_admin%&).
2660 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2661 is restricted to admin users unless &%queue_list_requires_admin%& is set
2666 &*Warning*&: If you configure your system so that admin users are able to
2667 edit Exim's configuration file, you are giving those users an easy way of
2668 getting root. There is further discussion of this issue at the start of chapter
2674 .section "Command line options" "SECID39"
2675 Exim's command line options are described in alphabetical order below. If none
2676 of the options that specifies a specific action (such as starting the daemon or
2677 a queue runner, or testing an address, or receiving a message in a specific
2678 format, or listing the queue) are present, and there is at least one argument
2679 on the command line, &%-bm%& (accept a local message on the standard input,
2680 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2681 outputs a brief message about itself and exits.
2683 . ////////////////////////////////////////////////////////////////////////////
2684 . Insert a stylized XML comment here, to identify the start of the command line
2685 . options. This is for the benefit of the Perl script that automatically
2686 . creates a man page for the options.
2687 . ////////////////////////////////////////////////////////////////////////////
2690 <!-- === Start of command line options === -->
2697 .cindex "options" "command line; terminating"
2698 This is a pseudo-option whose only purpose is to terminate the options and
2699 therefore to cause subsequent command line items to be treated as arguments
2700 rather than options, even if they begin with hyphens.
2703 .oindex "&%--help%&"
2704 This option causes Exim to output a few sentences stating what it is.
2705 The same output is generated if the Exim binary is called with no options and
2708 .vitem &%--version%&
2709 .oindex "&%--version%&"
2710 This option is an alias for &%-bV%& and causes version information to be
2717 These options are used by Sendmail for selecting configuration files and are
2720 .vitem &%-B%&<&'type'&>
2722 .cindex "8-bit characters"
2723 .cindex "Sendmail compatibility" "8-bit characters"
2724 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2725 clean; it ignores this option.
2730 .cindex "SMTP" "listener"
2731 .cindex "queue runner"
2732 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2733 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2734 that the daemon should also initiate periodic queue runs.
2736 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2737 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2738 disconnect from the controlling terminal. When running this way, it can be
2739 stopped by pressing ctrl-C.
2741 By default, Exim listens for incoming connections to the standard SMTP port on
2742 all the host's running interfaces. However, it is possible to listen on other
2743 ports, on multiple ports, and only on specific interfaces. Chapter
2744 &<<CHAPinterfaces>>& contains a description of the options that control this.
2746 When a listening daemon
2747 .cindex "daemon" "process id (pid)"
2748 .cindex "pid (process id)" "of daemon"
2749 is started without the use of &%-oX%& (that is, without overriding the normal
2750 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2751 in Exim's spool directory. This location can be overridden by setting
2752 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2755 When &%-oX%& is used on the command line to start a listening daemon, the
2756 process id is not written to the normal pid file path. However, &%-oP%& can be
2757 used to specify a path on the command line if a pid file is required.
2761 .cindex "daemon" "restarting"
2762 can be used to cause the daemon to re-execute itself. This should be done
2763 whenever Exim's configuration file, or any file that is incorporated into it by
2764 means of the &%.include%& facility, is changed, and also whenever a new version
2765 of Exim is installed. It is not necessary to do this when other files that are
2766 referenced from the configuration (for example, alias files) are changed,
2767 because these are reread each time they are used.
2771 This option has the same effect as &%-bd%& except that it never disconnects
2772 from the controlling terminal, even when no debugging is specified.
2776 .cindex "testing" "string expansion"
2777 .cindex "expansion" "testing"
2778 Run Exim in expansion testing mode. Exim discards its root privilege, to
2779 prevent ordinary users from using this mode to read otherwise inaccessible
2780 files. If no arguments are given, Exim runs interactively, prompting for lines
2781 of data. Otherwise, it processes each argument in turn.
2783 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2784 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2785 used without command line arguments. If successful, it uses the &[readline()]&
2786 function, which provides extensive line-editing facilities, for reading the
2787 test data. A line history is supported.
2789 Long expansion expressions can be split over several lines by using backslash
2790 continuations. As in Exim's run time configuration, white space at the start of
2791 continuation lines is ignored. Each argument or data line is passed through the
2792 string expansion mechanism, and the result is output. Variable values from the
2793 configuration file (for example, &$qualify_domain$&) are available, but no
2794 message-specific values (such as &$message_exim_id$&) are set, because no message
2795 is being processed (but see &%-bem%& and &%-Mset%&).
2797 &*Note*&: If you use this mechanism to test lookups, and you change the data
2798 files or databases you are using, you must exit and restart Exim before trying
2799 the same lookup again. Otherwise, because each Exim process caches the results
2800 of lookups, you will just get the same result as before.
2802 .vitem &%-bem%&&~<&'filename'&>
2804 .cindex "testing" "string expansion"
2805 .cindex "expansion" "testing"
2806 This option operates like &%-be%& except that it must be followed by the name
2807 of a file. For example:
2809 exim -bem /tmp/testmessage
2811 The file is read as a message (as if receiving a locally-submitted non-SMTP
2812 message) before any of the test expansions are done. Thus, message-specific
2813 variables such as &$message_size$& and &$header_from:$& are available. However,
2814 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2815 recipients are read from the headers in the normal way, and are shown in the
2816 &$recipients$& variable. Note that recipients cannot be given on the command
2817 line, because further arguments are taken as strings to expand (just like
2820 .vitem &%-bF%&&~<&'filename'&>
2822 .cindex "system filter" "testing"
2823 .cindex "testing" "system filter"
2824 This option is the same as &%-bf%& except that it assumes that the filter being
2825 tested is a system filter. The additional commands that are available only in
2826 system filters are recognized.
2828 .vitem &%-bf%&&~<&'filename'&>
2830 .cindex "filter" "testing"
2831 .cindex "testing" "filter file"
2832 .cindex "forward file" "testing"
2833 .cindex "testing" "forward file"
2834 .cindex "Sieve filter" "testing"
2835 This option runs Exim in user filter testing mode; the file is the filter file
2836 to be tested, and a test message must be supplied on the standard input. If
2837 there are no message-dependent tests in the filter, an empty file can be
2840 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2841 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2842 filter and a user filter in the same run. For example:
2844 exim -bF /system/filter -bf /user/filter </test/message
2846 This is helpful when the system filter adds header lines or sets filter
2847 variables that are used by the user filter.
2849 If the test filter file does not begin with one of the special lines
2854 it is taken to be a normal &_.forward_& file, and is tested for validity under
2855 that interpretation. See sections &<<SECTitenonfilred>>& to
2856 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2859 The result of an Exim command that uses &%-bf%&, provided no errors are
2860 detected, is a list of the actions that Exim would try to take if presented
2861 with the message for real. More details of filter testing are given in the
2862 separate document entitled &'Exim's interfaces to mail filtering'&.
2864 When testing a filter file,
2865 .cindex "&""From""& line"
2866 .cindex "envelope sender"
2867 .oindex "&%-f%&" "for filter testing"
2868 the envelope sender can be set by the &%-f%& option,
2869 or by a &"From&~"& line at the start of the test message. Various parameters
2870 that would normally be taken from the envelope recipient address of the message
2871 can be set by means of additional command line options (see the next four
2874 .vitem &%-bfd%&&~<&'domain'&>
2876 .vindex "&$qualify_domain$&"
2877 This sets the domain of the recipient address when a filter file is being
2878 tested by means of the &%-bf%& option. The default is the value of
2881 .vitem &%-bfl%&&~<&'local&~part'&>
2883 This sets the local part of the recipient address when a filter file is being
2884 tested by means of the &%-bf%& option. The default is the username of the
2885 process that calls Exim. A local part should be specified with any prefix or
2886 suffix stripped, because that is how it appears to the filter when a message is
2887 actually being delivered.
2889 .vitem &%-bfp%&&~<&'prefix'&>
2891 This sets the prefix of the local part of the recipient address when a filter
2892 file is being tested by means of the &%-bf%& option. The default is an empty
2895 .vitem &%-bfs%&&~<&'suffix'&>
2897 This sets the suffix of the local part of the recipient address when a filter
2898 file is being tested by means of the &%-bf%& option. The default is an empty
2901 .vitem &%-bh%&&~<&'IP&~address'&>
2903 .cindex "testing" "incoming SMTP"
2904 .cindex "SMTP" "testing incoming"
2905 .cindex "testing" "relay control"
2906 .cindex "relaying" "testing configuration"
2907 .cindex "policy control" "testing"
2908 .cindex "debugging" "&%-bh%& option"
2909 This option runs a fake SMTP session as if from the given IP address, using the
2910 standard input and output. The IP address may include a port number at the end,
2911 after a full stop. For example:
2913 exim -bh 10.9.8.7.1234
2914 exim -bh fe80::a00:20ff:fe86:a061.5678
2916 When an IPv6 address is given, it is converted into canonical form. In the case
2917 of the second example above, the value of &$sender_host_address$& after
2918 conversion to the canonical form is
2919 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2921 Comments as to what is going on are written to the standard error file. These
2922 include lines beginning with &"LOG"& for anything that would have been logged.
2923 This facility is provided for testing configuration options for incoming
2924 messages, to make sure they implement the required policy. For example, you can
2925 test your relay controls using &%-bh%&.
2929 You can test features of the configuration that rely on ident (RFC 1413)
2930 information by using the &%-oMt%& option. However, Exim cannot actually perform
2931 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2934 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2935 are also skipped when testing using &%-bh%&. If you want these callouts to
2936 occur, use &%-bhc%& instead.
2938 Messages supplied during the testing session are discarded, and nothing is
2939 written to any of the real log files. There may be pauses when DNS (and other)
2940 lookups are taking place, and of course these may time out. The &%-oMi%& option
2941 can be used to specify a specific IP interface and port if this is important,
2942 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2943 session were authenticated.
2945 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2946 output just states whether a given recipient address from a given host is
2947 acceptable or not. See section &<<SECTcheckaccess>>&.
2949 Features such as authentication and encryption, where the client input is not
2950 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2951 specialized SMTP test program such as
2952 &url(http://jetmore.org/john/code/#swaks,swaks).
2954 .vitem &%-bhc%&&~<&'IP&~address'&>
2956 This option operates in the same way as &%-bh%&, except that address
2957 verification callouts are performed if required. This includes consulting and
2958 updating the callout cache database.
2962 .cindex "alias file" "building"
2963 .cindex "building alias file"
2964 .cindex "Sendmail compatibility" "&%-bi%& option"
2965 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2966 Exim does not have the concept of a single alias file, and so it cannot mimic
2967 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2968 tend to appear in various scripts such as NIS make files, so the option must be
2971 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2972 configuration option is run, under the uid and gid of the caller of Exim. If
2973 the &%-oA%& option is used, its value is passed to the command as an argument.
2974 The command set by &%bi_command%& may not contain arguments. The command can
2975 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2976 if this is required. If the &%bi_command%& option is not set, calling Exim with
2979 . // Keep :help first, then the rest in alphabetical order
2981 .oindex "&%-bI:help%&"
2982 .cindex "querying exim information"
2983 We shall provide various options starting &`-bI:`& for querying Exim for
2984 information. The output of many of these will be intended for machine
2985 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2986 synopsis of supported options beginning &`-bI:`&. Use of any of these
2987 options shall cause Exim to exit after producing the requested output.
2990 .oindex "&%-bI:dscp%&"
2991 .cindex "DSCP" "values"
2992 This option causes Exim to emit an alphabetically sorted list of all
2993 recognised DSCP names.
2995 .vitem &%-bI:sieve%&
2996 .oindex "&%-bI:sieve%&"
2997 .cindex "Sieve filter" "capabilities"
2998 This option causes Exim to emit an alphabetically sorted list of all supported
2999 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3000 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3001 &`SIEVE`& capability response line. As the precise list may depend upon
3002 compile-time build options, which this option will adapt to, this is the only
3003 way to guarantee a correct response.
3007 .cindex "local message reception"
3008 This option runs an Exim receiving process that accepts an incoming,
3009 locally-generated message on the standard input. The recipients are given as the
3010 command arguments (except when &%-t%& is also present &-- see below). Each
3011 argument can be a comma-separated list of RFC 2822 addresses. This is the
3012 default option for selecting the overall action of an Exim call; it is assumed
3013 if no other conflicting option is present.
3015 If any addresses in the message are unqualified (have no domain), they are
3016 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3017 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3018 suppressing this for special cases.
3020 Policy checks on the contents of local messages can be enforced by means of
3021 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3023 .cindex "return code" "for &%-bm%&"
3024 The return code is zero if the message is successfully accepted. Otherwise, the
3025 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3028 .cindex "message" "format"
3029 .cindex "format" "message"
3030 .cindex "&""From""& line"
3031 .cindex "UUCP" "&""From""& line"
3032 .cindex "Sendmail compatibility" "&""From""& line"
3033 of the message must be as defined in RFC 2822, except that, for
3034 compatibility with Sendmail and Smail, a line in one of the forms
3036 From sender Fri Jan 5 12:55 GMT 1997
3037 From sender Fri, 5 Jan 97 12:55:01
3039 (with the weekday optional, and possibly with additional text after the date)
3040 is permitted to appear at the start of the message. There appears to be no
3041 authoritative specification of the format of this line. Exim recognizes it by
3042 matching against the regular expression defined by the &%uucp_from_pattern%&
3043 option, which can be changed if necessary.
3045 .oindex "&%-f%&" "overriding &""From""& line"
3046 The specified sender is treated as if it were given as the argument to the
3047 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3048 preference to the address taken from the message. The caller of Exim must be a
3049 trusted user for the sender of a message to be set in this way.
3051 .vitem &%-bmalware%&&~<&'filename'&>
3052 .oindex "&%-bmalware%&"
3053 .cindex "testing", "malware"
3054 .cindex "malware scan test"
3055 This debugging option causes Exim to scan the given file or directory
3056 (depending on the used scanner interface),
3057 using the malware scanning framework. The option of &%av_scanner%& influences
3058 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3059 the expansion should have defaults which apply to this invocation. ACLs are
3060 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3061 will never be populated and &%-bmalware%& will fail.
3063 Exim will have changed working directory before resolving the filename, so
3064 using fully qualified pathnames is advisable. Exim will be running as the Exim
3065 user when it tries to open the file, rather than as the invoking user.
3066 This option requires admin privileges.
3068 The &%-bmalware%& option will not be extended to be more generally useful,
3069 there are better tools for file-scanning. This option exists to help
3070 administrators verify their Exim and AV scanner configuration.
3074 .cindex "address qualification, suppressing"
3075 By default, Exim automatically qualifies unqualified addresses (those
3076 without domains) that appear in messages that are submitted locally (that
3077 is, not over TCP/IP). This qualification applies both to addresses in
3078 envelopes, and addresses in header lines. Sender addresses are qualified using
3079 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3080 defaults to the value of &%qualify_domain%&).
3082 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3083 being used to re-submit messages that originally came from remote hosts after
3084 content scanning, you probably do not want to qualify unqualified addresses in
3085 header lines. (Such lines will be present only if you have not enabled a header
3086 syntax check in the appropriate ACL.)
3088 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3089 messages that originate on the local host. When this is used, unqualified
3090 addresses in the envelope provoke errors (causing message rejection) and
3091 unqualified addresses in header lines are left alone.
3096 .cindex "configuration options" "extracting"
3097 .cindex "options" "configuration &-- extracting"
3098 If this option is given with no arguments, it causes the values of all Exim's
3099 main configuration options to be written to the standard output. The values
3100 of one or more specific options can be requested by giving their names as
3101 arguments, for example:
3103 exim -bP qualify_domain hold_domains
3105 .cindex "hiding configuration option values"
3106 .cindex "configuration options" "hiding value of"
3107 .cindex "options" "hiding value of"
3108 However, any option setting that is preceded by the word &"hide"& in the
3109 configuration file is not shown in full, except to an admin user. For other
3110 users, the output is as in this example:
3112 mysql_servers = <value not displayable>
3114 If &%config%& is given as an argument, the config is
3115 output, as it was parsed, any include file resolved, any comment removed.
3117 If &%config_file%& is given as an argument, the name of the run time
3118 configuration file is output. (&%configure_file%& works too, for
3119 backward compatibility.)
3120 If a list of configuration files was supplied, the value that is output here
3121 is the name of the file that was actually used.
3123 .cindex "options" "hiding name of"
3124 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3125 name will not be output.
3127 .cindex "daemon" "process id (pid)"
3128 .cindex "pid (process id)" "of daemon"
3129 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3130 directories where log files and daemon pid files are written are output,
3131 respectively. If these values are unset, log files are written in a
3132 sub-directory of the spool directory called &%log%&, and the pid file is
3133 written directly into the spool directory.
3135 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3137 exim -bP +local_domains
3139 it searches for a matching named list of any type (domain, host, address, or
3140 local part) and outputs what it finds.
3142 .cindex "options" "router &-- extracting"
3143 .cindex "options" "transport &-- extracting"
3144 .cindex "options" "authenticator &-- extracting"
3145 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3146 followed by the name of an appropriate driver instance, the option settings for
3147 that driver are output. For example:
3149 exim -bP transport local_delivery
3151 The generic driver options are output first, followed by the driver's private
3152 options. A list of the names of drivers of a particular type can be obtained by
3153 using one of the words &%router_list%&, &%transport_list%&, or
3154 &%authenticator_list%&, and a complete list of all drivers with their option
3155 settings can be obtained by using &%routers%&, &%transports%&, or
3158 .cindex "environment"
3159 If &%environment%& is given as an argument, the set of environment
3160 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3163 .cindex "options" "macro &-- extracting"
3164 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3165 are available, similarly to the drivers. Because macros are sometimes used
3166 for storing passwords, this option is restricted.
3167 The output format is one item per line.
3171 .cindex "queue" "listing messages on"
3172 .cindex "listing" "messages on the queue"
3173 This option requests a listing of the contents of the mail queue on the
3174 standard output. If the &%-bp%& option is followed by a list of message ids,
3175 just those messages are listed. By default, this option can be used only by an
3176 admin user. However, the &%queue_list_requires_admin%& option can be set false
3177 to allow any user to see the queue.
3179 Each message on the queue is displayed as in the following example:
3181 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3182 red.king@looking-glass.fict.example
3185 .cindex "message" "size in queue listing"
3186 .cindex "size" "of message"
3187 The first line contains the length of time the message has been on the queue
3188 (in this case 25 minutes), the size of the message (2.9K), the unique local
3189 identifier for the message, and the message sender, as contained in the
3190 envelope. For bounce messages, the sender address is empty, and appears as
3191 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3192 the default sender address, the user's login name is shown in parentheses
3193 before the sender address.
3195 .cindex "frozen messages" "in queue listing"
3196 If the message is frozen (attempts to deliver it are suspended) then the text
3197 &"*** frozen ***"& is displayed at the end of this line.
3199 The recipients of the message (taken from the envelope, not the headers) are
3200 displayed on subsequent lines. Those addresses to which the message has already
3201 been delivered are marked with the letter D. If an original address gets
3202 expanded into several addresses via an alias or forward file, the original is
3203 displayed with a D only when deliveries for all of its child addresses are
3209 This option operates like &%-bp%&, but in addition it shows delivered addresses
3210 that were generated from the original top level address(es) in each message by
3211 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3217 .cindex "queue" "count of messages on"
3218 This option counts the number of messages on the queue, and writes the total
3219 to the standard output. It is restricted to admin users, unless
3220 &%queue_list_requires_admin%& is set false.
3225 This option operates like &%-bp%&, but the output is not sorted into
3226 chronological order of message arrival. This can speed it up when there are
3227 lots of messages on the queue, and is particularly useful if the output is
3228 going to be post-processed in a way that doesn't need the sorting.
3232 This option is a combination of &%-bpr%& and &%-bpa%&.
3236 This option is a combination of &%-bpr%& and &%-bpu%&.
3241 This option operates like &%-bp%& but shows only undelivered top-level
3242 addresses for each message displayed. Addresses generated by aliasing or
3243 forwarding are not shown, unless the message was deferred after processing by a
3244 router with the &%one_time%& option set.
3249 .cindex "testing" "retry configuration"
3250 .cindex "retry" "configuration testing"
3251 This option is for testing retry rules, and it must be followed by up to three
3252 arguments. It causes Exim to look for a retry rule that matches the values
3253 and to write it to the standard output. For example:
3255 exim -brt bach.comp.mus.example
3256 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3258 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3259 argument, which is required, can be a complete address in the form
3260 &'local_part@domain'&, or it can be just a domain name. If the second argument
3261 contains a dot, it is interpreted as an optional second domain name; if no
3262 retry rule is found for the first argument, the second is tried. This ties in
3263 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3264 rule is found that matches the host, one that matches the mail domain is
3265 sought. Finally, an argument that is the name of a specific delivery error, as
3266 used in setting up retry rules, can be given. For example:
3268 exim -brt haydn.comp.mus.example quota_3d
3269 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3274 .cindex "testing" "rewriting"
3275 .cindex "rewriting" "testing"
3276 This option is for testing address rewriting rules, and it must be followed by
3277 a single argument, consisting of either a local part without a domain, or a
3278 complete address with a fully qualified domain. Exim outputs how this address
3279 would be rewritten for each possible place it might appear. See chapter
3280 &<<CHAPrewrite>>& for further details.
3284 .cindex "SMTP" "batched incoming"
3285 .cindex "batched SMTP input"
3286 This option is used for batched SMTP input, which is an alternative interface
3287 for non-interactive local message submission. A number of messages can be
3288 submitted in a single run. However, despite its name, this is not really SMTP
3289 input. Exim reads each message's envelope from SMTP commands on the standard
3290 input, but generates no responses. If the caller is trusted, or
3291 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3292 believed; otherwise the sender is always the caller of Exim.
3294 The message itself is read from the standard input, in SMTP format (leading
3295 dots doubled), terminated by a line containing just a single dot. An error is
3296 provoked if the terminating dot is missing. A further message may then follow.
3298 As for other local message submissions, the contents of incoming batch SMTP
3299 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3300 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3301 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3303 Some other SMTP commands are recognized in the input. HELO and EHLO act
3304 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3305 QUIT quits, ignoring the rest of the standard input.
3307 .cindex "return code" "for &%-bS%&"
3308 If any error is encountered, reports are written to the standard output and
3309 error streams, and Exim gives up immediately. The return code is 0 if no error
3310 was detected; it is 1 if one or more messages were accepted before the error
3311 was detected; otherwise it is 2.
3313 More details of input using batched SMTP are given in section
3314 &<<SECTincomingbatchedSMTP>>&.
3318 .cindex "SMTP" "local input"
3319 .cindex "local SMTP input"
3320 This option causes Exim to accept one or more messages by reading SMTP commands
3321 on the standard input, and producing SMTP replies on the standard output. SMTP
3322 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3323 Some user agents use this interface as a way of passing locally-generated
3324 messages to the MTA.
3327 .cindex "sender" "source of"
3328 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3329 set, the senders of messages are taken from the SMTP MAIL commands.
3330 Otherwise the content of these commands is ignored and the sender is set up as
3331 the calling user. Unqualified addresses are automatically qualified using
3332 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3333 &%-bnq%& option is used.
3337 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3338 using a listening daemon. Exim can distinguish the two cases by checking
3339 whether the standard input is a TCP/IP socket. When Exim is called from
3340 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3341 above concerning senders and qualification do not apply. In this situation,
3342 Exim behaves in exactly the same way as it does when receiving a message via
3343 the listening daemon.
3347 .cindex "testing" "addresses"
3348 .cindex "address" "testing"
3349 This option runs Exim in address testing mode, in which each argument is taken
3350 as a recipient address to be tested for deliverability. The results are
3351 written to the standard output. If a test fails, and the caller is not an admin
3352 user, no details of the failure are output, because these might contain
3353 sensitive information such as usernames and passwords for database lookups.
3355 If no arguments are given, Exim runs in an interactive manner, prompting with a
3356 right angle bracket for addresses to be tested.
3358 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3359 &[readline()]& function, because it is running as &'root'& and there are
3362 Each address is handled as if it were the recipient address of a message
3363 (compare the &%-bv%& option). It is passed to the routers and the result is
3364 written to the standard output. However, any router that has
3365 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3366 genuine routing tests if your first router passes everything to a scanner
3369 .cindex "return code" "for &%-bt%&"
3370 The return code is 2 if any address failed outright; it is 1 if no address
3371 failed outright but at least one could not be resolved for some reason. Return
3372 code 0 is given only when all addresses succeed.
3374 .cindex "duplicate addresses"
3375 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3376 addresses after routing is complete, so that only one delivery takes place.
3377 This does not happen when testing with &%-bt%&; the full results of routing are
3380 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3381 routers in the configuration makes any tests on the sender address of a
3383 .oindex "&%-f%&" "for address testing"
3384 you can use the &%-f%& option to set an appropriate sender when running
3385 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3386 default qualifying domain. However, if you have set up (for example) routers
3387 whose behaviour depends on the contents of an incoming message, you cannot test
3388 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3393 .cindex "version number of Exim"
3394 This option causes Exim to write the current version number, compilation
3395 number, and compilation date of the &'exim'& binary to the standard output.
3396 It also lists the DBM library that is being used, the optional modules (such as
3397 specific lookup types), the drivers that are included in the binary, and the
3398 name of the run time configuration file that is in use.
3400 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3401 configuration file. However, this is a static check only. It cannot check
3402 values that are to be expanded. For example, although a misspelt ACL verb is
3403 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3404 alone to discover (for example) all the typos in the configuration; some
3405 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3406 dynamic testing facilities.
3410 .cindex "verifying address" "using &%-bv%&"
3411 .cindex "address" "verification"
3412 This option runs Exim in address verification mode, in which each argument is
3413 taken as a recipient address to be verified by the routers. (This does
3414 not involve any verification callouts). During normal operation, verification
3415 happens mostly as a consequence processing a &%verify%& condition in an ACL
3416 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3417 including callouts, see the &%-bh%& and &%-bhc%& options.
3419 If verification fails, and the caller is not an admin user, no details of the
3420 failure are output, because these might contain sensitive information such as
3421 usernames and passwords for database lookups.
3423 If no arguments are given, Exim runs in an interactive manner, prompting with a
3424 right angle bracket for addresses to be verified.
3426 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3427 &[readline()]& function, because it is running as &'exim'& and there are
3430 Verification differs from address testing (the &%-bt%& option) in that routers
3431 that have &%no_verify%& set are skipped, and if the address is accepted by a
3432 router that has &%fail_verify%& set, verification fails. The address is
3433 verified as a recipient if &%-bv%& is used; to test verification for a sender
3434 address, &%-bvs%& should be used.
3436 If the &%-v%& option is not set, the output consists of a single line for each
3437 address, stating whether it was verified or not, and giving a reason in the
3438 latter case. Without &%-v%&, generating more than one address by redirection
3439 causes verification to end successfully, without considering the generated
3440 addresses. However, if just one address is generated, processing continues,
3441 and the generated address must verify successfully for the overall verification
3444 When &%-v%& is set, more details are given of how the address has been handled,
3445 and in the case of address redirection, all the generated addresses are also
3446 considered. Verification may succeed for some and fail for others.
3449 .cindex "return code" "for &%-bv%&"
3450 return code is 2 if any address failed outright; it is 1 if no address
3451 failed outright but at least one could not be resolved for some reason. Return
3452 code 0 is given only when all addresses succeed.
3454 If any of the routers in the configuration makes any tests on the sender
3455 address of a message, you should use the &%-f%& option to set an appropriate
3456 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3457 calling user at the default qualifying domain.
3461 This option acts like &%-bv%&, but verifies the address as a sender rather
3462 than a recipient address. This affects any rewriting and qualification that
3469 .cindex "inetd" "wait mode"
3470 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3471 similarly to the &%-bd%& option. All port specifications on the command-line
3472 and in the configuration file are ignored. Queue-running may not be specified.
3474 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3475 listening for connections. This permits the system to start up and have
3476 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3477 each port only when the first connection is received.
3479 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3480 which the daemon will exit, which should cause inetd to listen once more.
3482 .vitem &%-C%&&~<&'filelist'&>
3484 .cindex "configuration file" "alternate"
3485 .cindex "CONFIGURE_FILE"
3486 .cindex "alternate configuration file"
3487 This option causes Exim to find the run time configuration file from the given
3488 list instead of from the list specified by the CONFIGURE_FILE
3489 compile-time setting. Usually, the list will consist of just a single file
3490 name, but it can be a colon-separated list of names. In this case, the first
3491 file that exists is used. Failure to open an existing file stops Exim from
3492 proceeding any further along the list, and an error is generated.
3494 When this option is used by a caller other than root, and the list is different
3495 from the compiled-in list, Exim gives up its root privilege immediately, and
3496 runs with the real and effective uid and gid set to those of the caller.
3497 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3498 file contains a list of full pathnames, one per line, for configuration files
3499 which are trusted. Root privilege is retained for any configuration file so
3500 listed, as long as the caller is the Exim user (or the user specified in the
3501 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3502 not writeable by inappropriate users or groups.
3504 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3505 configuration using &%-C%& right through message reception and delivery,
3506 even if the caller is root. The reception works, but by that time, Exim is
3507 running as the Exim user, so when it re-executes to regain privilege for the
3508 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3509 test reception and delivery using two separate commands (one to put a message
3510 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3512 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3513 prefix string with which any file named in a &%-C%& command line option
3514 must start. In addition, the file name must not contain the sequence &`/../`&.
3515 However, if the value of the &%-C%& option is identical to the value of
3516 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3517 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3518 unset, any file name can be used with &%-C%&.
3520 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3521 to a directory to which only root has access. This prevents someone who has
3522 broken into the Exim account from running a privileged Exim with an arbitrary
3525 The &%-C%& facility is useful for ensuring that configuration files are
3526 syntactically correct, but cannot be used for test deliveries, unless the
3527 caller is privileged, or unless it is an exotic configuration that does not
3528 require privilege. No check is made on the owner or group of the files
3529 specified by this option.
3532 .vitem &%-D%&<&'macro'&>=<&'value'&>
3534 .cindex "macro" "setting on command line"
3535 This option can be used to override macro definitions in the configuration file
3536 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3537 unprivileged caller, it causes Exim to give up its root privilege.
3538 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3539 completely disabled, and its use causes an immediate error exit.
3541 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3542 colon-separated list of macros which are considered safe and, if &%-D%& only
3543 supplies macros from this list, and the values are acceptable, then Exim will
3544 not give up root privilege if the caller is root, the Exim run-time user, or
3545 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3546 to be removed in the future. Acceptable values for the macros satisfy the
3547 regexp: &`^[A-Za-z0-9_/.-]*$`&
3549 The entire option (including equals sign if present) must all be within one
3550 command line item. &%-D%& can be used to set the value of a macro to the empty
3551 string, in which case the equals sign is optional. These two commands are
3557 To include spaces in a macro definition item, quotes must be used. If you use
3558 quotes, spaces are permitted around the macro name and the equals sign. For
3561 exim '-D ABC = something' ...
3563 &%-D%& may be repeated up to 10 times on a command line.
3564 Only macro names up to 22 letters long can be set.
3567 .vitem &%-d%&<&'debug&~options'&>
3569 .cindex "debugging" "list of selectors"
3570 .cindex "debugging" "&%-d%& option"
3571 This option causes debugging information to be written to the standard
3572 error stream. It is restricted to admin users because debugging output may show
3573 database queries that contain password information. Also, the details of users'
3574 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3575 writes an error message to the standard error stream and exits with a non-zero
3578 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3579 standard debugging data is output. This can be reduced, or increased to include
3580 some more rarely needed information, by directly following &%-d%& with a string
3581 made up of names preceded by plus or minus characters. These add or remove sets
3582 of debugging data, respectively. For example, &%-d+filter%& adds filter
3583 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3584 no spaces are allowed in the debug setting. The available debugging categories
3587 &`acl `& ACL interpretation
3588 &`auth `& authenticators
3589 &`deliver `& general delivery logic
3590 &`dns `& DNS lookups (see also resolver)
3591 &`dnsbl `& DNS black list (aka RBL) code
3592 &`exec `& arguments for &[execv()]& calls
3593 &`expand `& detailed debugging for string expansions
3594 &`filter `& filter handling
3595 &`hints_lookup `& hints data lookups
3596 &`host_lookup `& all types of name-to-IP address handling
3597 &`ident `& ident lookup
3598 &`interface `& lists of local interfaces
3599 &`lists `& matching things in lists
3600 &`load `& system load checks
3601 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3602 &<<CHAPlocalscan>>&)
3603 &`lookup `& general lookup code and all lookups
3604 &`memory `& memory handling
3605 &`pid `& add pid to debug output lines
3606 &`process_info `& setting info for the process log
3607 &`queue_run `& queue runs
3608 &`receive `& general message reception logic
3609 &`resolver `& turn on the DNS resolver's debugging output
3610 &`retry `& retry handling
3611 &`rewrite `& address rewriting
3612 &`route `& address routing
3613 &`timestamp `& add timestamp to debug output lines
3615 &`transport `& transports
3616 &`uid `& changes of uid/gid and looking up uid/gid
3617 &`verify `& address verification logic
3618 &`all `& almost all of the above (see below), and also &%-v%&
3620 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3621 for &`-all`&. The reason for this is that &`+all`& is something that people
3622 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3623 is included, an awful lot of output that is very rarely of interest is
3624 generated, so it now has to be explicitly requested. However, &`-all`& does
3625 turn everything off.
3627 .cindex "resolver, debugging output"
3628 .cindex "DNS resolver, debugging output"
3629 The &`resolver`& option produces output only if the DNS resolver was compiled
3630 with DEBUG enabled. This is not the case in some operating systems. Also,
3631 unfortunately, debugging output from the DNS resolver is written to stdout
3634 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3635 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3636 However, the &`pid`& selector is forced when debugging is turned on for a
3637 daemon, which then passes it on to any re-executed Exims. Exim also
3638 automatically adds the pid to debug lines when several remote deliveries are
3641 The &`timestamp`& selector causes the current time to be inserted at the start
3642 of all debug output lines. This can be useful when trying to track down delays
3645 If the &%debug_print%& option is set in any driver, it produces output whenever
3646 any debugging is selected, or if &%-v%& is used.
3648 .vitem &%-dd%&<&'debug&~options'&>
3650 This option behaves exactly like &%-d%& except when used on a command that
3651 starts a daemon process. In that case, debugging is turned off for the
3652 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3653 behaviour of the daemon without creating as much output as full debugging does.
3656 .oindex "&%-dropcr%&"
3657 This is an obsolete option that is now a no-op. It used to affect the way Exim
3658 handled CR and LF characters in incoming messages. What happens now is
3659 described in section &<<SECTlineendings>>&.
3663 .cindex "bounce message" "generating"
3664 This option specifies that an incoming message is a locally-generated delivery
3665 failure report. It is used internally by Exim when handling delivery failures
3666 and is not intended for external use. Its only effect is to stop Exim
3667 generating certain messages to the postmaster, as otherwise message cascades
3668 could occur in some situations. As part of the same option, a message id may
3669 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3670 new message contains the id, following &"R="&, as a cross-reference.
3673 .oindex "&%-e%&&'x'&"
3674 There are a number of Sendmail options starting with &%-oe%& which seem to be
3675 called by various programs without the leading &%o%& in the option. For
3676 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3677 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3679 .vitem &%-F%&&~<&'string'&>
3681 .cindex "sender" "name"
3682 .cindex "name" "of sender"
3683 This option sets the sender's full name for use when a locally-generated
3684 message is being accepted. In the absence of this option, the user's &'gecos'&
3685 entry from the password data is used. As users are generally permitted to alter
3686 their &'gecos'& entries, no security considerations are involved. White space
3687 between &%-F%& and the <&'string'&> is optional.
3689 .vitem &%-f%&&~<&'address'&>
3691 .cindex "sender" "address"
3692 .cindex "address" "sender"
3693 .cindex "trusted users"
3694 .cindex "envelope sender"
3695 .cindex "user" "trusted"
3696 This option sets the address of the envelope sender of a locally-generated
3697 message (also known as the return path). The option can normally be used only
3698 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3701 Processes running as root or the Exim user are always trusted. Other
3702 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3703 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3704 of a local message is set to the caller's login name at the default qualify
3707 There is one exception to the restriction on the use of &%-f%&: an empty sender
3708 can be specified by any user, trusted or not, to create a message that can
3709 never provoke a bounce. An empty sender can be specified either as an empty
3710 string, or as a pair of angle brackets with nothing between them, as in these
3711 examples of shell commands:
3713 exim -f '<>' user@domain
3714 exim -f "" user@domain
3716 In addition, the use of &%-f%& is not restricted when testing a filter file
3717 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3720 Allowing untrusted users to change the sender address does not of itself make
3721 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3722 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3723 though this can be overridden by setting &%no_local_from_check%&.
3726 .cindex "&""From""& line"
3727 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3728 given as two arguments or one combined argument). The sender of a
3729 locally-generated message can also be set (when permitted) by an initial
3730 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3731 if &%-f%& is also present, it overrides &"From&~"&.
3735 .cindex "submission fixups, suppressing (command-line)"
3736 This option is equivalent to an ACL applying:
3738 control = suppress_local_fixups
3740 for every message received. Note that Sendmail will complain about such
3741 bad formatting, where Exim silently just does not fix it up. This may change
3744 As this affects audit information, the caller must be a trusted user to use
3747 .vitem &%-h%&&~<&'number'&>
3749 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3750 This option is accepted for compatibility with Sendmail, but has no effect. (In
3751 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3756 .cindex "Solaris" "&'mail'& command"
3757 .cindex "dot" "in incoming non-SMTP message"
3758 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3759 line by itself should not terminate an incoming, non-SMTP message. I can find
3760 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3761 command in Solaris 2.4 uses it. See also &%-ti%&.
3763 .vitem &%-L%&&~<&'tag'&>
3765 .cindex "syslog" "process name; set with flag"
3766 This option is equivalent to setting &%syslog_processname%& in the config
3767 file and setting &%log_file_path%& to &`syslog`&.
3768 Its use is restricted to administrators. The configuration file has to be
3769 read and parsed, to determine access rights, before this is set and takes
3770 effect, so early configuration file errors will not honour this flag.
3772 The tag should not be longer than 32 characters.
3774 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3776 .cindex "forcing delivery"
3777 .cindex "delivery" "forcing attempt"
3778 .cindex "frozen messages" "forcing delivery"
3779 This option requests Exim to run a delivery attempt on each message in turn. If
3780 any of the messages are frozen, they are automatically thawed before the
3781 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3782 and &%hold_domains%& are ignored.
3785 .cindex "hints database" "overriding retry hints"
3786 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3787 the normal retry time has not yet been reached. This option requires the caller
3788 to be an admin user. However, there is an option called &%prod_requires_admin%&
3789 which can be set false to relax this restriction (and also the same requirement
3790 for the &%-q%&, &%-R%&, and &%-S%& options).
3792 The deliveries happen synchronously, that is, the original Exim process does
3793 not terminate until all the delivery attempts have finished. No output is
3794 produced unless there is a serious error. If you want to see what is happening,
3795 use the &%-v%& option as well, or inspect Exim's main log.
3797 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3799 .cindex "message" "adding recipients"
3800 .cindex "recipient" "adding"
3801 This option requests Exim to add the addresses to the list of recipients of the
3802 message (&"ar"& for &"add recipients"&). The first argument must be a message
3803 id, and the remaining ones must be email addresses. However, if the message is
3804 active (in the middle of a delivery attempt), it is not altered. This option
3805 can be used only by an admin user.
3807 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3808 &~<&'message&~id'&>"
3810 .cindex "SMTP" "passed connection"
3811 .cindex "SMTP" "multiple deliveries"
3812 .cindex "multiple SMTP deliveries"
3813 This option is not intended for use by external callers. It is used internally
3814 by Exim to invoke another instance of itself to deliver a waiting message using
3815 an existing SMTP connection, which is passed as the standard input. Details are
3816 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3817 must be root or the Exim user in order to use it.
3821 This option is not intended for use by external callers. It is used internally
3822 by Exim in conjunction with the &%-MC%& option. It signifies that the
3823 connection to the remote host has been authenticated.
3827 This option is not intended for use by external callers. It is used internally
3828 by Exim in conjunction with the &%-MC%& option. It signifies that the
3829 remote host supports the ESMTP &_DSN_& extension.
3833 This option is not intended for use by external callers. It is used internally
3834 by Exim in conjunction with the &%-MC%& option. It signifies that an
3835 alternate queue is used, named by the following argument.
3839 This option is not intended for use by external callers. It is used internally
3840 by Exim in conjunction with the &%-MC%& option. It signifies that an
3841 remote host supports the ESMTP &_CHUNKING_& extension.
3845 This option is not intended for use by external callers. It is used internally
3846 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3847 which Exim is connected supports pipelining.
3849 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3851 This option is not intended for use by external callers. It is used internally
3852 by Exim in conjunction with the &%-MC%& option when the original delivery was
3853 started by a queue runner. It passes on the process id of the queue runner,
3854 together with the file descriptor number of an open pipe. Closure of the pipe
3855 signals the final completion of the sequence of processes that are passing
3856 messages through the same SMTP connection.
3860 This option is not intended for use by external callers. It is used internally
3861 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3862 SMTP SIZE option should be used on messages delivered down the existing
3867 This option is not intended for use by external callers. It is used internally
3868 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3869 host to which Exim is connected supports TLS encryption.
3871 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3873 .cindex "hints database" "not overridden by &%-Mc%&"
3874 .cindex "delivery" "manually started &-- not forced"
3875 This option requests Exim to run a delivery attempt on each message in turn,
3876 but unlike the &%-M%& option, it does check for retry hints, and respects any
3877 that are found. This option is not very useful to external callers. It is
3878 provided mainly for internal use by Exim when it needs to re-invoke itself in
3879 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3880 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3881 respects retry times and other options such as &%hold_domains%& that are
3882 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3883 If you want to run a specific delivery as if in a queue run, you should use
3884 &%-q%& with a message id argument. A distinction between queue run deliveries
3885 and other deliveries is made in one or two places.
3887 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3889 .cindex "message" "changing sender"
3890 .cindex "sender" "changing"
3891 This option requests Exim to change the sender address in the message to the
3892 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3893 &"edit sender"&). There must be exactly two arguments. The first argument must
3894 be a message id, and the second one an email address. However, if the message
3895 is active (in the middle of a delivery attempt), its status is not altered.
3896 This option can be used only by an admin user.
3898 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3900 .cindex "freezing messages"
3901 .cindex "message" "manually freezing"
3902 This option requests Exim to mark each listed message as &"frozen"&. This
3903 prevents any delivery attempts taking place until the message is &"thawed"&,
3904 either manually or as a result of the &%auto_thaw%& configuration option.
3905 However, if any of the messages are active (in the middle of a delivery
3906 attempt), their status is not altered. This option can be used only by an admin
3909 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3911 .cindex "giving up on messages"
3912 .cindex "message" "abandoning delivery attempts"
3913 .cindex "delivery" "abandoning further attempts"
3914 This option requests Exim to give up trying to deliver the listed messages,
3915 including any that are frozen. However, if any of the messages are active,
3916 their status is not altered. For non-bounce messages, a delivery error message
3917 is sent to the sender, containing the text &"cancelled by administrator"&.
3918 Bounce messages are just discarded. This option can be used only by an admin
3921 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3923 .cindex "delivery" "cancelling all"
3924 This option requests Exim to mark all the recipient addresses in the messages
3925 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3926 message is active (in the middle of a delivery attempt), its status is not
3927 altered. This option can be used only by an admin user.
3929 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3931 .cindex "delivery" "cancelling by address"
3932 .cindex "recipient" "removing"
3933 .cindex "removing recipients"
3934 This option requests Exim to mark the given addresses as already delivered
3935 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3936 the remaining ones must be email addresses. These are matched to recipient
3937 addresses in the message in a case-sensitive manner. If the message is active
3938 (in the middle of a delivery attempt), its status is not altered. This option
3939 can be used only by an admin user.
3941 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3943 .cindex "removing messages"
3944 .cindex "abandoning mail"
3945 .cindex "message" "manually discarding"
3946 This option requests Exim to remove the given messages from the queue. No
3947 bounce messages are sent; each message is simply forgotten. However, if any of
3948 the messages are active, their status is not altered. This option can be used
3949 only by an admin user or by the user who originally caused the message to be
3950 placed on the queue.
3952 .vitem &%-Mset%&&~<&'message&~id'&>
3954 .cindex "testing" "string expansion"
3955 .cindex "expansion" "testing"
3956 This option is useful only in conjunction with &%-be%& (that is, when testing
3957 string expansions). Exim loads the given message from its spool before doing
3958 the test expansions, thus setting message-specific variables such as
3959 &$message_size$& and the header variables. The &$recipients$& variable is made
3960 available. This feature is provided to make it easier to test expansions that
3961 make use of these variables. However, this option can be used only by an admin
3962 user. See also &%-bem%&.
3964 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3966 .cindex "thawing messages"
3967 .cindex "unfreezing messages"
3968 .cindex "frozen messages" "thawing"
3969 .cindex "message" "thawing frozen"
3970 This option requests Exim to &"thaw"& any of the listed messages that are
3971 &"frozen"&, so that delivery attempts can resume. However, if any of the
3972 messages are active, their status is not altered. This option can be used only
3975 .vitem &%-Mvb%&&~<&'message&~id'&>
3977 .cindex "listing" "message body"
3978 .cindex "message" "listing body of"
3979 This option causes the contents of the message body (-D) spool file to be
3980 written to the standard output. This option can be used only by an admin user.
3982 .vitem &%-Mvc%&&~<&'message&~id'&>
3984 .cindex "message" "listing in RFC 2822 format"
3985 .cindex "listing" "message in RFC 2822 format"
3986 This option causes a copy of the complete message (header lines plus body) to
3987 be written to the standard output in RFC 2822 format. This option can be used
3988 only by an admin user.
3990 .vitem &%-Mvh%&&~<&'message&~id'&>
3992 .cindex "listing" "message headers"
3993 .cindex "header lines" "listing"
3994 .cindex "message" "listing header lines"
3995 This option causes the contents of the message headers (-H) spool file to be
3996 written to the standard output. This option can be used only by an admin user.
3998 .vitem &%-Mvl%&&~<&'message&~id'&>
4000 .cindex "listing" "message log"
4001 .cindex "message" "listing message log"
4002 This option causes the contents of the message log spool file to be written to
4003 the standard output. This option can be used only by an admin user.
4007 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4008 treats it that way too.
4012 .cindex "debugging" "&%-N%& option"
4013 .cindex "debugging" "suppressing delivery"
4014 This is a debugging option that inhibits delivery of a message at the transport
4015 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4016 it just doesn't actually transport the message, but instead behaves as if it
4017 had successfully done so. However, it does not make any updates to the retry
4018 database, and the log entries for deliveries are flagged with &"*>"& rather
4021 Because &%-N%& discards any message to which it applies, only root or the Exim
4022 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4023 words, an ordinary user can use it only when supplying an incoming message to
4024 which it will apply. Although transportation never fails when &%-N%& is set, an
4025 address may be deferred because of a configuration problem on a transport, or a
4026 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4027 the message, and applies to any subsequent delivery attempts that may happen
4032 This option is interpreted by Sendmail to mean &"no aliasing"&.
4033 For normal modes of operation, it is ignored by Exim.
4034 When combined with &%-bP%& it makes the output more terse (suppresses
4035 option names, environment values and config pretty printing).
4037 .vitem &%-O%&&~<&'data'&>
4039 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4042 .vitem &%-oA%&&~<&'file&~name'&>
4044 .cindex "Sendmail compatibility" "&%-oA%& option"
4045 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4046 alternative alias file name. Exim handles &%-bi%& differently; see the
4049 .vitem &%-oB%&&~<&'n'&>
4051 .cindex "SMTP" "passed connection"
4052 .cindex "SMTP" "multiple deliveries"
4053 .cindex "multiple SMTP deliveries"
4054 This is a debugging option which limits the maximum number of messages that can
4055 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4056 transport. If <&'n'&> is omitted, the limit is set to 1.
4060 .cindex "background delivery"
4061 .cindex "delivery" "in the background"
4062 This option applies to all modes in which Exim accepts incoming messages,
4063 including the listening daemon. It requests &"background"& delivery of such
4064 messages, which means that the accepting process automatically starts a
4065 delivery process for each message received, but does not wait for the delivery
4066 processes to finish.
4068 When all the messages have been received, the reception process exits,
4069 leaving the delivery processes to finish in their own time. The standard output
4070 and error streams are closed at the start of each delivery process.
4071 This is the default action if none of the &%-od%& options are present.
4073 If one of the queueing options in the configuration file
4074 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4075 overrides it if &%queue_only_override%& is set true, which is the default
4076 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4080 .cindex "foreground delivery"
4081 .cindex "delivery" "in the foreground"
4082 This option requests &"foreground"& (synchronous) delivery when Exim has
4083 accepted a locally-generated message. (For the daemon it is exactly the same as
4084 &%-odb%&.) A delivery process is automatically started to deliver the message,
4085 and Exim waits for it to complete before proceeding.
4087 The original Exim reception process does not finish until the delivery
4088 process for the final message has ended. The standard error stream is left open
4091 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4092 false and one of the queueing options in the configuration file is in effect.
4094 If there is a temporary delivery error during foreground delivery, the
4095 message is left on the queue for later delivery, and the original reception
4096 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4097 restricted configuration that never queues messages.
4102 This option is synonymous with &%-odf%&. It is provided for compatibility with
4107 .cindex "non-immediate delivery"
4108 .cindex "delivery" "suppressing immediate"
4109 .cindex "queueing incoming messages"
4110 This option applies to all modes in which Exim accepts incoming messages,
4111 including the listening daemon. It specifies that the accepting process should
4112 not automatically start a delivery process for each message received. Messages
4113 are placed on the queue, and remain there until a subsequent queue runner
4114 process encounters them. There are several configuration options (such as
4115 &%queue_only%&) that can be used to queue incoming messages under certain
4116 conditions. This option overrides all of them and also &%-odqs%&. It always
4121 .cindex "SMTP" "delaying delivery"
4122 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4123 However, like &%-odb%& and &%-odi%&, this option has no effect if
4124 &%queue_only_override%& is false and one of the queueing options in the
4125 configuration file is in effect.
4127 When &%-odqs%& does operate, a delivery process is started for each incoming
4128 message, in the background by default, but in the foreground if &%-odi%& is
4129 also present. The recipient addresses are routed, and local deliveries are done
4130 in the normal way. However, if any SMTP deliveries are required, they are not
4131 done at this time, so the message remains on the queue until a subsequent queue
4132 runner process encounters it. Because routing was done, Exim knows which
4133 messages are waiting for which hosts, and so a number of messages for the same
4134 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4135 configuration option has the same effect for specific domains. See also the
4140 .cindex "error" "reporting"
4141 If an error is detected while a non-SMTP message is being received (for
4142 example, a malformed address), the error is reported to the sender in a mail
4145 .cindex "return code" "for &%-oee%&"
4147 this error message is successfully sent, the Exim receiving process
4148 exits with a return code of zero. If not, the return code is 2 if the problem
4149 is that the original message has no recipients, or 1 for any other error.
4150 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4154 .cindex "error" "reporting"
4155 .cindex "return code" "for &%-oem%&"
4156 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4157 return code, whether or not the error message was successfully sent.
4158 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4162 .cindex "error" "reporting"
4163 If an error is detected while a non-SMTP message is being received, the
4164 error is reported by writing a message to the standard error file (stderr).
4165 .cindex "return code" "for &%-oep%&"
4166 The return code is 1 for all errors.
4170 .cindex "error" "reporting"
4171 This option is supported for compatibility with Sendmail, but has the same
4176 .cindex "error" "reporting"
4177 This option is supported for compatibility with Sendmail, but has the same
4182 .cindex "dot" "in incoming non-SMTP message"
4183 This option, which has the same effect as &%-i%&, specifies that a dot on a
4184 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4185 single dot does terminate, though Exim does no special processing for other
4186 lines that start with a dot. This option is set by default if Exim is called as
4187 &'rmail'&. See also &%-ti%&.
4190 .oindex "&%-oitrue%&"
4191 This option is treated as synonymous with &%-oi%&.
4193 .vitem &%-oMa%&&~<&'host&~address'&>
4195 .cindex "sender" "host address, specifying for local message"
4196 A number of options starting with &%-oM%& can be used to set values associated
4197 with remote hosts on locally-submitted messages (that is, messages not received
4198 over TCP/IP). These options can be used by any caller in conjunction with the
4199 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4200 other circumstances, they are ignored unless the caller is trusted.
4202 The &%-oMa%& option sets the sender host address. This may include a port
4203 number at the end, after a full stop (period). For example:
4205 exim -bs -oMa 10.9.8.7.1234
4207 An alternative syntax is to enclose the IP address in square brackets,
4208 followed by a colon and the port number:
4210 exim -bs -oMa [10.9.8.7]:1234
4212 The IP address is placed in the &$sender_host_address$& variable, and the
4213 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4214 are present on the command line, the sender host IP address is taken from
4215 whichever one is last.
4217 .vitem &%-oMaa%&&~<&'name'&>
4219 .cindex "authentication" "name, specifying for local message"
4220 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4221 option sets the value of &$sender_host_authenticated$& (the authenticator
4222 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4223 This option can be used with &%-bh%& and &%-bs%& to set up an
4224 authenticated SMTP session without actually using the SMTP AUTH command.
4226 .vitem &%-oMai%&&~<&'string'&>
4228 .cindex "authentication" "id, specifying for local message"
4229 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4230 option sets the value of &$authenticated_id$& (the id that was authenticated).
4231 This overrides the default value (the caller's login id, except with &%-bh%&,
4232 where there is no default) for messages from local sources. See chapter
4233 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4235 .vitem &%-oMas%&&~<&'address'&>
4237 .cindex "authentication" "sender, specifying for local message"
4238 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4239 option sets the authenticated sender value in &$authenticated_sender$&. It
4240 overrides the sender address that is created from the caller's login id for
4241 messages from local sources, except when &%-bh%& is used, when there is no
4242 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4243 specified on a MAIL command overrides this value. See chapter
4244 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4246 .vitem &%-oMi%&&~<&'interface&~address'&>
4248 .cindex "interface" "address, specifying for local message"
4249 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4250 option sets the IP interface address value. A port number may be included,
4251 using the same syntax as for &%-oMa%&. The interface address is placed in
4252 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4254 .vitem &%-oMm%&&~<&'message&~reference'&>
4256 .cindex "message reference" "message reference, specifying for local message"
4257 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4258 option sets the message reference, e.g. message-id, and is logged during
4259 delivery. This is useful when some kind of audit trail is required to tie
4260 messages together. The format of the message reference is checked and will
4261 abort if the format is invalid. The option will only be accepted if exim is
4262 running in trusted mode, not as any regular user.
4264 The best example of a message reference is when Exim sends a bounce message.
4265 The message reference is the message-id of the original message for which Exim
4266 is sending the bounce.
4268 .vitem &%-oMr%&&~<&'protocol&~name'&>
4270 .cindex "protocol, specifying for local message"
4271 .vindex "&$received_protocol$&"
4272 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4273 option sets the received protocol value that is stored in
4274 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4275 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4276 SMTP protocol names (see the description of &$received_protocol$& in section
4277 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4278 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4281 .vitem &%-oMs%&&~<&'host&~name'&>
4283 .cindex "sender" "host name, specifying for local message"
4284 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4285 option sets the sender host name in &$sender_host_name$&. When this option is
4286 present, Exim does not attempt to look up a host name from an IP address; it
4287 uses the name it is given.
4289 .vitem &%-oMt%&&~<&'ident&~string'&>
4291 .cindex "sender" "ident string, specifying for local message"
4292 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4293 option sets the sender ident value in &$sender_ident$&. The default setting for
4294 local callers is the login id of the calling process, except when &%-bh%& is
4295 used, when there is no default.
4299 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4300 In Sendmail, this option means &"me too"&, indicating that the sender of a
4301 message should receive a copy of the message if the sender appears in an alias
4302 expansion. Exim always does this, so the option does nothing.
4306 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4307 This option is ignored. In Sendmail it specifies &"old style headers"&,
4308 whatever that means.
4310 .vitem &%-oP%&&~<&'path'&>
4312 .cindex "pid (process id)" "of daemon"
4313 .cindex "daemon" "process id (pid)"
4314 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4315 value. The option specifies the file to which the process id of the daemon is
4316 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4317 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4318 because in those cases, the normal pid file is not used.
4320 .vitem &%-or%&&~<&'time'&>
4322 .cindex "timeout" "for non-SMTP input"
4323 This option sets a timeout value for incoming non-SMTP messages. If it is not
4324 set, Exim will wait forever for the standard input. The value can also be set
4325 by the &%receive_timeout%& option. The format used for specifying times is
4326 described in section &<<SECTtimeformat>>&.
4328 .vitem &%-os%&&~<&'time'&>
4330 .cindex "timeout" "for SMTP input"
4331 .cindex "SMTP" "input timeout"
4332 This option sets a timeout value for incoming SMTP messages. The timeout
4333 applies to each SMTP command and block of data. The value can also be set by
4334 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4335 for specifying times is described in section &<<SECTtimeformat>>&.
4339 This option has exactly the same effect as &%-v%&.
4341 .vitem &%-oX%&&~<&'number&~or&~string'&>
4343 .cindex "TCP/IP" "setting listening ports"
4344 .cindex "TCP/IP" "setting listening interfaces"
4345 .cindex "port" "receiving TCP/IP"
4346 This option is relevant only when the &%-bd%& (start listening daemon) option
4347 is also given. It controls which ports and interfaces the daemon uses. Details
4348 of the syntax, and how it interacts with configuration file options, are given
4349 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4350 file is written unless &%-oP%& is also present to specify a pid file name.
4354 .cindex "Perl" "starting the interpreter"
4355 This option applies when an embedded Perl interpreter is linked with Exim (see
4356 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4357 option, forcing the starting of the interpreter to be delayed until it is
4362 .cindex "Perl" "starting the interpreter"
4363 This option applies when an embedded Perl interpreter is linked with Exim (see
4364 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4365 option, forcing the starting of the interpreter to occur as soon as Exim is
4368 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4370 For compatibility with Sendmail, this option is equivalent to
4372 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4374 It sets the incoming protocol and host name (for trusted callers). The
4375 host name and its colon can be omitted when only the protocol is to be set.
4376 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4377 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4378 or &`s`& using this option (but that does not seem a real limitation).
4382 .cindex "queue runner" "starting manually"
4383 This option is normally restricted to admin users. However, there is a
4384 configuration option called &%prod_requires_admin%& which can be set false to
4385 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4386 and &%-S%& options).
4388 .cindex "queue runner" "description of operation"
4389 If other commandline options do not specify an action,
4390 the &%-q%& option starts one queue runner process. This scans the queue of
4391 waiting messages, and runs a delivery process for each one in turn. It waits
4392 for each delivery process to finish before starting the next one. A delivery
4393 process may not actually do any deliveries if the retry times for the addresses
4394 have not been reached. Use &%-qf%& (see below) if you want to override this.
4397 .cindex "SMTP" "passed connection"
4398 .cindex "SMTP" "multiple deliveries"
4399 .cindex "multiple SMTP deliveries"
4400 the delivery process spawns other processes to deliver other messages down
4401 passed SMTP connections, the queue runner waits for these to finish before
4404 When all the queued messages have been considered, the original queue runner
4405 process terminates. In other words, a single pass is made over the waiting
4406 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4407 this to be repeated periodically.
4409 Exim processes the waiting messages in an unpredictable order. It isn't very
4410 random, but it is likely to be different each time, which is all that matters.
4411 If one particular message screws up a remote MTA, other messages to the same
4412 MTA have a chance of getting through if they get tried first.
4414 It is possible to cause the messages to be processed in lexical message id
4415 order, which is essentially the order in which they arrived, by setting the
4416 &%queue_run_in_order%& option, but this is not recommended for normal use.
4418 .vitem &%-q%&<&'qflags'&>
4419 The &%-q%& option may be followed by one or more flag letters that change its
4420 behaviour. They are all optional, but if more than one is present, they must
4421 appear in the correct order. Each flag is described in a separate item below.
4425 .cindex "queue" "double scanning"
4426 .cindex "queue" "routing"
4427 .cindex "routing" "whole queue before delivery"
4428 An option starting with &%-qq%& requests a two-stage queue run. In the first
4429 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4430 every domain. Addresses are routed, local deliveries happen, but no remote
4433 .cindex "hints database" "remembering routing"
4434 The hints database that remembers which messages are waiting for specific hosts
4435 is updated, as if delivery to those hosts had been deferred. After this is
4436 complete, a second, normal queue scan happens, with routing and delivery taking
4437 place as normal. Messages that are routed to the same host should mostly be
4438 delivered down a single SMTP
4439 .cindex "SMTP" "passed connection"
4440 .cindex "SMTP" "multiple deliveries"
4441 .cindex "multiple SMTP deliveries"
4442 connection because of the hints that were set up during the first queue scan.
4443 This option may be useful for hosts that are connected to the Internet
4446 .vitem &%-q[q]i...%&
4448 .cindex "queue" "initial delivery"
4449 If the &'i'& flag is present, the queue runner runs delivery processes only for
4450 those messages that haven't previously been tried. (&'i'& stands for &"initial
4451 delivery"&.) This can be helpful if you are putting messages on the queue using
4452 &%-odq%& and want a queue runner just to process the new messages.
4454 .vitem &%-q[q][i]f...%&
4456 .cindex "queue" "forcing delivery"
4457 .cindex "delivery" "forcing in queue run"
4458 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4459 message, whereas without &'f'& only those non-frozen addresses that have passed
4460 their retry times are tried.
4462 .vitem &%-q[q][i]ff...%&
4464 .cindex "frozen messages" "forcing delivery"
4465 If &'ff'& is present, a delivery attempt is forced for every message, whether
4468 .vitem &%-q[q][i][f[f]]l%&
4470 .cindex "queue" "local deliveries only"
4471 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4472 be done. If a message requires any remote deliveries, it remains on the queue
4475 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4478 .cindex "named queues"
4479 .cindex "queue" "delivering specific messages"
4480 If the &'G'& flag and a name is present, the queue runner operates on the
4481 queue with the given name rather than the default queue.
4482 The name should not contain a &'/'& character.
4483 For a periodic queue run (see below)
4484 append to the name a slash and a time value.
4486 If other commandline options specify an action, a &'-qG<name>'& option
4487 will specify a queue to operate on.
4490 exim -bp -qGquarantine
4492 exim -qGoffpeak -Rf @special.domain.example
4495 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4496 When scanning the queue, Exim can be made to skip over messages whose ids are
4497 lexically less than a given value by following the &%-q%& option with a
4498 starting message id. For example:
4500 exim -q 0t5C6f-0000c8-00
4502 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4503 second message id is given, messages whose ids are lexically greater than it
4504 are also skipped. If the same id is given twice, for example,
4506 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4508 just one delivery process is started, for that message. This differs from
4509 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4510 that it counts as a delivery from a queue run. Note that the selection
4511 mechanism does not affect the order in which the messages are scanned. There
4512 are also other ways of selecting specific sets of messages for delivery in a
4513 queue run &-- see &%-R%& and &%-S%&.
4515 .vitem &%-q%&<&'qflags'&><&'time'&>
4516 .cindex "queue runner" "starting periodically"
4517 .cindex "periodic queue running"
4518 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4519 starting a queue runner process at intervals specified by the given time value
4520 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4521 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4522 single daemon process handles both functions. A common way of starting up a
4523 combined daemon at system boot time is to use a command such as
4525 /usr/exim/bin/exim -bd -q30m
4527 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4528 process every 30 minutes.
4530 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4531 pid file is written unless one is explicitly requested by the &%-oP%& option.
4533 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4535 This option is synonymous with &%-R%&. It is provided for Sendmail
4538 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4540 This option is synonymous with &%-S%&.
4542 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4544 .cindex "queue runner" "for specific recipients"
4545 .cindex "delivery" "to given domain"
4546 .cindex "domain" "delivery to"
4547 The <&'rsflags'&> may be empty, in which case the white space before the string
4548 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4549 which are the possible values for <&'rsflags'&>. White space is required if
4550 <&'rsflags'&> is not empty.
4552 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4553 perform a single queue run, except that, when scanning the messages on the
4554 queue, Exim processes only those that have at least one undelivered recipient
4555 address containing the given string, which is checked in a case-independent
4556 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4557 regular expression; otherwise it is a literal string.
4559 If you want to do periodic queue runs for messages with specific recipients,
4560 you can combine &%-R%& with &%-q%& and a time value. For example:
4562 exim -q25m -R @special.domain.example
4564 This example does a queue run for messages with recipients in the given domain
4565 every 25 minutes. Any additional flags that are specified with &%-q%& are
4566 applied to each queue run.
4568 Once a message is selected for delivery by this mechanism, all its addresses
4569 are processed. For the first selected message, Exim overrides any retry
4570 information and forces a delivery attempt for each undelivered address. This
4571 means that if delivery of any address in the first message is successful, any
4572 existing retry information is deleted, and so delivery attempts for that
4573 address in subsequently selected messages (which are processed without forcing)
4574 will run. However, if delivery of any address does not succeed, the retry
4575 information is updated, and in subsequently selected messages, the failing
4576 address will be skipped.
4578 .cindex "frozen messages" "forcing delivery"
4579 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4580 all selected messages, not just the first; frozen messages are included when
4583 The &%-R%& option makes it straightforward to initiate delivery of all messages
4584 to a given domain after a host has been down for some time. When the SMTP
4585 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4586 effect is to run Exim with the &%-R%& option, but it can be configured to run
4587 an arbitrary command instead.
4591 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4593 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4595 .cindex "delivery" "from given sender"
4596 .cindex "queue runner" "for specific senders"
4597 This option acts like &%-R%& except that it checks the string against each
4598 message's sender instead of against the recipients. If &%-R%& is also set, both
4599 conditions must be met for a message to be selected. If either of the options
4600 has &'f'& or &'ff'& in its flags, the associated action is taken.
4602 .vitem &%-Tqt%&&~<&'times'&>
4604 This is an option that is exclusively for use by the Exim testing suite. It is not
4605 recognized when Exim is run normally. It allows for the setting up of explicit
4606 &"queue times"& so that various warning/retry features can be tested.
4610 .cindex "recipient" "extracting from header lines"
4611 .cindex "&'Bcc:'& header line"
4612 .cindex "&'Cc:'& header line"
4613 .cindex "&'To:'& header line"
4614 When Exim is receiving a locally-generated, non-SMTP message on its standard
4615 input, the &%-t%& option causes the recipients of the message to be obtained
4616 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4617 from the command arguments. The addresses are extracted before any rewriting
4618 takes place and the &'Bcc:'& header line, if present, is then removed.
4620 .cindex "Sendmail compatibility" "&%-t%& option"
4621 If the command has any arguments, they specify addresses to which the message
4622 is &'not'& to be delivered. That is, the argument addresses are removed from
4623 the recipients list obtained from the headers. This is compatible with Smail 3
4624 and in accordance with the documented behaviour of several versions of
4625 Sendmail, as described in man pages on a number of operating systems (e.g.
4626 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4627 argument addresses to those obtained from the headers, and the O'Reilly
4628 Sendmail book documents it that way. Exim can be made to add argument addresses
4629 instead of subtracting them by setting the option
4630 &%extract_addresses_remove_arguments%& false.
4632 .cindex "&%Resent-%& header lines" "with &%-t%&"
4633 If there are any &%Resent-%& header lines in the message, Exim extracts
4634 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4635 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4636 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4637 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4639 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4640 message is resent several times). The RFC also specifies that they should be
4641 added at the front of the message, and separated by &'Received:'& lines. It is
4642 not at all clear how &%-t%& should operate in the present of multiple sets,
4643 nor indeed exactly what constitutes a &"set"&.
4644 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4645 are often added at the end of the header, and if a message is resent more than
4646 once, it is common for the original set of &%Resent-%& headers to be renamed as
4647 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4651 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4652 compatibility with Sendmail.
4654 .vitem &%-tls-on-connect%&
4655 .oindex "&%-tls-on-connect%&"
4656 .cindex "TLS" "use without STARTTLS"
4657 .cindex "TLS" "automatic start"
4658 This option is available when Exim is compiled with TLS support. It forces all
4659 incoming SMTP connections to behave as if the incoming port is listed in the
4660 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4661 &<<CHAPTLS>>& for further details.
4666 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4667 Sendmail uses this option for &"initial message submission"&, and its
4668 documentation states that in future releases, it may complain about
4669 syntactically invalid messages rather than fixing them when this flag is not
4670 set. Exim ignores this option.
4674 This option causes Exim to write information to the standard error stream,
4675 describing what it is doing. In particular, it shows the log lines for
4676 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4677 dialogue is shown. Some of the log lines shown may not actually be written to
4678 the log if the setting of &%log_selector%& discards them. Any relevant
4679 selectors are shown with each log line. If none are shown, the logging is
4684 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4685 National Language Support extended characters in the body of the mail item"&).
4686 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4689 .vitem &%-X%&&~<&'logfile'&>
4691 This option is interpreted by Sendmail to cause debug information to be sent
4692 to the named file. It is ignored by Exim.
4694 .vitem &%-z%&&~<&'log-line'&>
4696 This option writes its argument to Exim's logfile.
4697 Use is restricted to administrators; the intent is for operational notes.
4698 Quotes should be used to maintain a multi-word item as a single argument,
4706 . ////////////////////////////////////////////////////////////////////////////
4707 . Insert a stylized DocBook comment here, to identify the end of the command
4708 . line options. This is for the benefit of the Perl script that automatically
4709 . creates a man page for the options.
4710 . ////////////////////////////////////////////////////////////////////////////
4713 <!-- === End of command line options === -->
4720 . ////////////////////////////////////////////////////////////////////////////
4721 . ////////////////////////////////////////////////////////////////////////////
4724 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4725 "The runtime configuration file"
4727 .cindex "run time configuration"
4728 .cindex "configuration file" "general description"
4729 .cindex "CONFIGURE_FILE"
4730 .cindex "configuration file" "errors in"
4731 .cindex "error" "in configuration file"
4732 .cindex "return code" "for bad configuration"
4733 Exim uses a single run time configuration file that is read whenever an Exim
4734 binary is executed. Note that in normal operation, this happens frequently,
4735 because Exim is designed to operate in a distributed manner, without central
4738 If a syntax error is detected while reading the configuration file, Exim
4739 writes a message on the standard error, and exits with a non-zero return code.
4740 The message is also written to the panic log. &*Note*&: Only simple syntax
4741 errors can be detected at this time. The values of any expanded options are
4742 not checked until the expansion happens, even when the expansion does not
4743 actually alter the string.
4745 The name of the configuration file is compiled into the binary for security
4746 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4747 most configurations, this specifies a single file. However, it is permitted to
4748 give a colon-separated list of file names, in which case Exim uses the first
4749 existing file in the list.
4752 .cindex "EXIM_GROUP"
4753 .cindex "CONFIGURE_OWNER"
4754 .cindex "CONFIGURE_GROUP"
4755 .cindex "configuration file" "ownership"
4756 .cindex "ownership" "configuration file"
4757 The run time configuration file must be owned by root or by the user that is
4758 specified at compile time by the CONFIGURE_OWNER option (if set). The
4759 configuration file must not be world-writeable, or group-writeable unless its
4760 group is the root group or the one specified at compile time by the
4761 CONFIGURE_GROUP option.
4763 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4764 to root, anybody who is able to edit the run time configuration file has an
4765 easy way to run commands as root. If you specify a user or group in the
4766 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4767 who are members of that group will trivially be able to obtain root privileges.
4769 Up to Exim version 4.72, the run time configuration file was also permitted to
4770 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4771 since it offered a simple privilege escalation for any attacker who managed to
4772 compromise the Exim user account.
4774 A default configuration file, which will work correctly in simple situations,
4775 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4776 defines just one file name, the installation process copies the default
4777 configuration to a new file of that name if it did not previously exist. If
4778 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4779 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4784 .section "Using a different configuration file" "SECID40"
4785 .cindex "configuration file" "alternate"
4786 A one-off alternate configuration can be specified by the &%-C%& command line
4787 option, which may specify a single file or a list of files. However, when
4788 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4789 unless the argument for &%-C%& is identical to the built-in value from
4790 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4791 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4792 is useful mainly for checking the syntax of configuration files before
4793 installing them. No owner or group checks are done on a configuration file
4794 specified by &%-C%&, if root privilege has been dropped.
4796 Even the Exim user is not trusted to specify an arbitrary configuration file
4797 with the &%-C%& option to be used with root privileges, unless that file is
4798 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4799 testing a configuration using &%-C%& right through message reception and
4800 delivery, even if the caller is root. The reception works, but by that time,
4801 Exim is running as the Exim user, so when it re-execs to regain privilege for
4802 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4803 can test reception and delivery using two separate commands (one to put a
4804 message on the queue, using &%-odq%&, and another to do the delivery, using
4807 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4808 prefix string with which any file named in a &%-C%& command line option must
4809 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4810 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4811 name can be used with &%-C%&.
4813 One-off changes to a configuration can be specified by the &%-D%& command line
4814 option, which defines and overrides values for macros used inside the
4815 configuration file. However, like &%-C%&, the use of this option by a
4816 non-privileged user causes Exim to discard its root privilege.
4817 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4818 completely disabled, and its use causes an immediate error exit.
4820 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4821 to declare certain macro names trusted, such that root privilege will not
4822 necessarily be discarded.
4823 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4824 considered safe and, if &%-D%& only supplies macros from this list, and the
4825 values are acceptable, then Exim will not give up root privilege if the caller
4826 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4827 transition mechanism and is expected to be removed in the future. Acceptable
4828 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4830 Some sites may wish to use the same Exim binary on different machines that
4831 share a file system, but to use different configuration files on each machine.
4832 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4833 looks for a file whose name is the configuration file name followed by a dot
4834 and the machine's node name, as obtained from the &[uname()]& function. If this
4835 file does not exist, the standard name is tried. This processing occurs for
4836 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4838 In some esoteric situations different versions of Exim may be run under
4839 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4840 help with this. See the comments in &_src/EDITME_& for details.
4844 .section "Configuration file format" "SECTconffilfor"
4845 .cindex "configuration file" "format of"
4846 .cindex "format" "configuration file"
4847 Exim's configuration file is divided into a number of different parts. General
4848 option settings must always appear at the start of the file. The other parts
4849 are all optional, and may appear in any order. Each part other than the first
4850 is introduced by the word &"begin"& followed by at least one literal
4851 space, and the name of the part. The optional parts are:
4854 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4857 .cindex "AUTH" "configuration"
4858 &'authenticators'&: Configuration settings for the authenticator drivers. These
4859 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4861 &'routers'&: Configuration settings for the router drivers. Routers process
4862 addresses and determine how the message is to be delivered (see chapters
4863 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4865 &'transports'&: Configuration settings for the transport drivers. Transports
4866 define mechanisms for copying messages to destinations (see chapters
4867 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4869 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4870 If there is no retry section, or if it is empty (that is, no retry rules are
4871 defined), Exim will not retry deliveries. In this situation, temporary errors
4872 are treated the same as permanent errors. Retry rules are discussed in chapter
4875 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4876 when new addresses are generated during delivery. Rewriting is discussed in
4877 chapter &<<CHAPrewrite>>&.
4879 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4880 want to use this feature, you must set
4882 LOCAL_SCAN_HAS_OPTIONS=yes
4884 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4885 facility are given in chapter &<<CHAPlocalscan>>&.
4888 .cindex "configuration file" "leading white space in"
4889 .cindex "configuration file" "trailing white space in"
4890 .cindex "white space" "in configuration file"
4891 Leading and trailing white space in configuration lines is always ignored.
4893 Blank lines in the file, and lines starting with a # character (ignoring
4894 leading white space) are treated as comments and are ignored. &*Note*&: A
4895 # character other than at the beginning of a line is not treated specially,
4896 and does not introduce a comment.
4898 Any non-comment line can be continued by ending it with a backslash. Note that
4899 the general rule for white space means that trailing white space after the
4900 backslash and leading white space at the start of continuation
4901 lines is ignored. Comment lines beginning with # (but not empty lines) may
4902 appear in the middle of a sequence of continuation lines.
4904 A convenient way to create a configuration file is to start from the
4905 default, which is supplied in &_src/configure.default_&, and add, delete, or
4906 change settings as required.
4908 The ACLs, retry rules, and rewriting rules have their own syntax which is
4909 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4910 respectively. The other parts of the configuration file have some syntactic
4911 items in common, and these are described below, from section &<<SECTcos>>&
4912 onwards. Before that, the inclusion, macro, and conditional facilities are
4917 .section "File inclusions in the configuration file" "SECID41"
4918 .cindex "inclusions in configuration file"
4919 .cindex "configuration file" "including other files"
4920 .cindex "&`.include`& in configuration file"
4921 .cindex "&`.include_if_exists`& in configuration file"
4922 You can include other files inside Exim's run time configuration file by
4925 &`.include`& <&'file name'&>
4926 &`.include_if_exists`& <&'file name'&>
4928 on a line by itself. Double quotes round the file name are optional. If you use
4929 the first form, a configuration error occurs if the file does not exist; the
4930 second form does nothing for non-existent files.
4931 The first form allows a relative name. It is resolved relative to
4932 the directory of the including file. For the second form an absolute file
4935 Includes may be nested to any depth, but remember that Exim reads its
4936 configuration file often, so it is a good idea to keep them to a minimum.
4937 If you change the contents of an included file, you must HUP the daemon,
4938 because an included file is read only when the configuration itself is read.
4940 The processing of inclusions happens early, at a physical line level, so, like
4941 comment lines, an inclusion can be used in the middle of an option setting,
4944 hosts_lookup = a.b.c \
4947 Include processing happens after macro processing (see below). Its effect is to
4948 process the lines of the included file as if they occurred inline where the
4953 .section "Macros in the configuration file" "SECTmacrodefs"
4954 .cindex "macro" "description of"
4955 .cindex "configuration file" "macros"
4956 If a line in the main part of the configuration (that is, before the first
4957 &"begin"& line) begins with an upper case letter, it is taken as a macro
4958 definition, and must be of the form
4960 <&'name'&> = <&'rest of line'&>
4962 The name must consist of letters, digits, and underscores, and need not all be
4963 in upper case, though that is recommended. The rest of the line, including any
4964 continuations, is the replacement text, and has leading and trailing white
4965 space removed. Quotes are not removed. The replacement text can never end with
4966 a backslash character, but this doesn't seem to be a serious limitation.
4968 Macros may also be defined between router, transport, authenticator, or ACL
4969 definitions. They may not, however, be defined within an individual driver or
4970 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4972 .section "Macro substitution" "SECID42"
4973 Once a macro is defined, all subsequent lines in the file (and any included
4974 files) are scanned for the macro name; if there are several macros, the line is
4975 scanned for each in turn, in the order in which the macros are defined. The
4976 replacement text is not re-scanned for the current macro, though it is scanned
4977 for subsequently defined macros. For this reason, a macro name may not contain
4978 the name of a previously defined macro as a substring. You could, for example,
4981 &`ABCD_XYZ = `&<&'something'&>
4982 &`ABCD = `&<&'something else'&>
4984 but putting the definitions in the opposite order would provoke a configuration
4985 error. Macro expansion is applied to individual physical lines from the file,
4986 before checking for line continuation or file inclusion (see above). If a line
4987 consists solely of a macro name, and the expansion of the macro is empty, the
4988 line is ignored. A macro at the start of a line may turn the line into a
4989 comment line or a &`.include`& line.
4992 .section "Redefining macros" "SECID43"
4993 Once defined, the value of a macro can be redefined later in the configuration
4994 (or in an included file). Redefinition is specified by using &'=='& instead of
4999 MAC == updated value
5001 Redefinition does not alter the order in which the macros are applied to the
5002 subsequent lines of the configuration file. It is still the same order in which
5003 the macros were originally defined. All that changes is the macro's value.
5004 Redefinition makes it possible to accumulate values. For example:
5008 MAC == MAC and something added
5010 This can be helpful in situations where the configuration file is built
5011 from a number of other files.
5013 .section "Overriding macro values" "SECID44"
5014 The values set for macros in the configuration file can be overridden by the
5015 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5016 used, unless called by root or the Exim user. A definition on the command line
5017 using the &%-D%& option causes all definitions and redefinitions within the
5022 .section "Example of macro usage" "SECID45"
5023 As an example of macro usage, consider a configuration where aliases are looked
5024 up in a MySQL database. It helps to keep the file less cluttered if long
5025 strings such as SQL statements are defined separately as macros, for example:
5027 ALIAS_QUERY = select mailbox from user where \
5028 login='${quote_mysql:$local_part}';
5030 This can then be used in a &(redirect)& router setting like this:
5032 data = ${lookup mysql{ALIAS_QUERY}}
5034 In earlier versions of Exim macros were sometimes used for domain, host, or
5035 address lists. In Exim 4 these are handled better by named lists &-- see
5036 section &<<SECTnamedlists>>&.
5039 .section "Builtin macros" "SECTbuiltinmacros"
5040 Exim defines some macros depending on facilities available, which may
5041 differ due to build-time definitions and from one release to another.
5042 All of these macros start with an underscore.
5043 They can be used to conditionally include parts of a configuration
5046 The following classes of macros are defined:
5048 &` _HAVE_* `& build-time defines
5049 &` _DRIVER_ROUTER_* `& router drivers
5050 &` _DRIVER_TRANSPORT_* `& transport drivers
5051 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5052 &` _OPT_MAIN_* `& main config options
5053 &` _OPT_ROUTERS_* `& generic router options
5054 &` _OPT_TRANSPORTS_* `& generic transport options
5055 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5056 &` _OPT_ROUTER_*_* `& private router options
5057 &` _OPT_TRANSPORT_*_* `& private transport options
5058 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5061 Use an &"exim -bP macros"& command to get the list of macros.
5064 .section "Conditional skips in the configuration file" "SECID46"
5065 .cindex "configuration file" "conditional skips"
5066 .cindex "&`.ifdef`&"
5067 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5068 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5069 portions of the configuration file. The processing happens whenever the file is
5070 read (that is, when an Exim binary starts to run).
5072 The implementation is very simple. Instances of the first four directives must
5073 be followed by text that includes the names of one or macros. The condition
5074 that is tested is whether or not any macro substitution has taken place in the
5078 message_size_limit = 50M
5080 message_size_limit = 100M
5083 sets a message size limit of 50M if the macro &`AAA`& is defined
5084 (or &`A`& or &`AA`&), and 100M
5085 otherwise. If there is more than one macro named on the line, the condition
5086 is true if any of them are defined. That is, it is an &"or"& condition. To
5087 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5089 Although you can use a macro expansion to generate one of these directives,
5090 it is not very useful, because the condition &"there was a macro substitution
5091 in this line"& will always be true.
5093 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5094 to clarify complicated nestings.
5098 .section "Common option syntax" "SECTcos"
5099 .cindex "common option syntax"
5100 .cindex "syntax of common options"
5101 .cindex "configuration file" "common option syntax"
5102 For the main set of options, driver options, and &[local_scan()]& options,
5103 each setting is on a line by itself, and starts with a name consisting of
5104 lower-case letters and underscores. Many options require a data value, and in
5105 these cases the name must be followed by an equals sign (with optional white
5106 space) and then the value. For example:
5108 qualify_domain = mydomain.example.com
5110 .cindex "hiding configuration option values"
5111 .cindex "configuration options" "hiding value of"
5112 .cindex "options" "hiding value of"
5113 Some option settings may contain sensitive data, for example, passwords for
5114 accessing databases. To stop non-admin users from using the &%-bP%& command
5115 line option to read these values, you can precede the option settings with the
5116 word &"hide"&. For example:
5118 hide mysql_servers = localhost/users/admin/secret-password
5120 For non-admin users, such options are displayed like this:
5122 mysql_servers = <value not displayable>
5124 If &"hide"& is used on a driver option, it hides the value of that option on
5125 all instances of the same driver.
5127 The following sections describe the syntax used for the different data types
5128 that are found in option settings.
5131 .section "Boolean options" "SECID47"
5132 .cindex "format" "boolean"
5133 .cindex "boolean configuration values"
5134 .oindex "&%no_%&&'xxx'&"
5135 .oindex "&%not_%&&'xxx'&"
5136 Options whose type is given as boolean are on/off switches. There are two
5137 different ways of specifying such options: with and without a data value. If
5138 the option name is specified on its own without data, the switch is turned on;
5139 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5140 boolean options may be followed by an equals sign and one of the words
5141 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5142 the following two settings have exactly the same effect:
5147 The following two lines also have the same (opposite) effect:
5152 You can use whichever syntax you prefer.
5157 .section "Integer values" "SECID48"
5158 .cindex "integer configuration values"
5159 .cindex "format" "integer"
5160 If an option's type is given as &"integer"&, the value can be given in decimal,
5161 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5162 number is assumed. Otherwise, it is treated as an octal number unless it starts
5163 with the characters &"0x"&, in which case the remainder is interpreted as a
5166 If an integer value is followed by the letter K, it is multiplied by 1024; if
5167 it is followed by the letter M, it is multiplied by 1024x1024;
5168 if by the letter G, 1024x1024x1024.
5170 of integer option settings are output, values which are an exact multiple of
5171 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5172 and M. The printing style is independent of the actual input format that was
5176 .section "Octal integer values" "SECID49"
5177 .cindex "integer format"
5178 .cindex "format" "octal integer"
5179 If an option's type is given as &"octal integer"&, its value is always
5180 interpreted as an octal number, whether or not it starts with the digit zero.
5181 Such options are always output in octal.
5184 .section "Fixed point numbers" "SECID50"
5185 .cindex "fixed point configuration values"
5186 .cindex "format" "fixed point"
5187 If an option's type is given as &"fixed-point"&, its value must be a decimal
5188 integer, optionally followed by a decimal point and up to three further digits.
5192 .section "Time intervals" "SECTtimeformat"
5193 .cindex "time interval" "specifying in configuration"
5194 .cindex "format" "time interval"
5195 A time interval is specified as a sequence of numbers, each followed by one of
5196 the following letters, with no intervening white space:
5206 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5207 intervals are output in the same format. Exim does not restrict the values; it
5208 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5212 .section "String values" "SECTstrings"
5213 .cindex "string" "format of configuration values"
5214 .cindex "format" "string"
5215 If an option's type is specified as &"string"&, the value can be specified with
5216 or without double-quotes. If it does not start with a double-quote, the value
5217 consists of the remainder of the line plus any continuation lines, starting at
5218 the first character after any leading white space, with trailing white space
5219 removed, and with no interpretation of the characters in the string. Because
5220 Exim removes comment lines (those beginning with #) at an early stage, they can
5221 appear in the middle of a multi-line string. The following two settings are
5222 therefore equivalent:
5224 trusted_users = uucp:mail
5225 trusted_users = uucp:\
5226 # This comment line is ignored
5229 .cindex "string" "quoted"
5230 .cindex "escape characters in quoted strings"
5231 If a string does start with a double-quote, it must end with a closing
5232 double-quote, and any backslash characters other than those used for line
5233 continuation are interpreted as escape characters, as follows:
5236 .irow &`\\`& "single backslash"
5237 .irow &`\n`& "newline"
5238 .irow &`\r`& "carriage return"
5240 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5241 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5245 If a backslash is followed by some other character, including a double-quote
5246 character, that character replaces the pair.
5248 Quoting is necessary only if you want to make use of the backslash escapes to
5249 insert special characters, or if you need to specify a value with leading or
5250 trailing spaces. These cases are rare, so quoting is almost never needed in
5251 current versions of Exim. In versions of Exim before 3.14, quoting was required
5252 in order to continue lines, so you may come across older configuration files
5253 and examples that apparently quote unnecessarily.
5256 .section "Expanded strings" "SECID51"
5257 .cindex "expansion" "definition of"
5258 Some strings in the configuration file are subjected to &'string expansion'&,
5259 by which means various parts of the string may be changed according to the
5260 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5261 is as just described; in particular, the handling of backslashes in quoted
5262 strings is done as part of the input process, before expansion takes place.
5263 However, backslash is also an escape character for the expander, so any
5264 backslashes that are required for that reason must be doubled if they are
5265 within a quoted configuration string.
5268 .section "User and group names" "SECID52"
5269 .cindex "user name" "format of"
5270 .cindex "format" "user name"
5271 .cindex "groups" "name format"
5272 .cindex "format" "group name"
5273 User and group names are specified as strings, using the syntax described
5274 above, but the strings are interpreted specially. A user or group name must
5275 either consist entirely of digits, or be a name that can be looked up using the
5276 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5279 .section "List construction" "SECTlistconstruct"
5280 .cindex "list" "syntax of in configuration"
5281 .cindex "format" "list item in configuration"
5282 .cindex "string" "list, definition of"
5283 The data for some configuration options is a list of items, with colon as the
5284 default separator. Many of these options are shown with type &"string list"& in
5285 the descriptions later in this document. Others are listed as &"domain list"&,
5286 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5287 are all the same; however, those other than &"string list"& are subject to
5288 particular kinds of interpretation, as described in chapter
5289 &<<CHAPdomhosaddlists>>&.
5291 In all these cases, the entire list is treated as a single string as far as the
5292 input syntax is concerned. The &%trusted_users%& setting in section
5293 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5294 in a list, it must be entered as two colons. Leading and trailing white space
5295 on each item in a list is ignored. This makes it possible to include items that
5296 start with a colon, and in particular, certain forms of IPv6 address. For
5299 local_interfaces = 127.0.0.1 : ::::1
5301 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5303 &*Note*&: Although leading and trailing white space is ignored in individual
5304 list items, it is not ignored when parsing the list. The space after the first
5305 colon in the example above is necessary. If it were not there, the list would
5306 be interpreted as the two items 127.0.0.1:: and 1.
5308 .section "Changing list separators" "SECTlistsepchange"
5309 .cindex "list separator" "changing"
5310 .cindex "IPv6" "addresses in lists"
5311 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5312 introduced to allow the separator character to be changed. If a list begins
5313 with a left angle bracket, followed by any punctuation character, that
5314 character is used instead of colon as the list separator. For example, the list
5315 above can be rewritten to use a semicolon separator like this:
5317 local_interfaces = <; 127.0.0.1 ; ::1
5319 This facility applies to all lists, with the exception of the list in
5320 &%log_file_path%&. It is recommended that the use of non-colon separators be
5321 confined to circumstances where they really are needed.
5323 .cindex "list separator" "newline as"
5324 .cindex "newline" "as list separator"
5325 It is also possible to use newline and other control characters (those with
5326 code values less than 32, plus DEL) as separators in lists. Such separators
5327 must be provided literally at the time the list is processed. For options that
5328 are string-expanded, you can write the separator using a normal escape
5329 sequence. This will be processed by the expander before the string is
5330 interpreted as a list. For example, if a newline-separated list of domains is
5331 generated by a lookup, you can process it directly by a line such as this:
5333 domains = <\n ${lookup mysql{.....}}
5335 This avoids having to change the list separator in such data. You are unlikely
5336 to want to use a control character as a separator in an option that is not
5337 expanded, because the value is literal text. However, it can be done by giving
5338 the value in quotes. For example:
5340 local_interfaces = "<\n 127.0.0.1 \n ::1"
5342 Unlike printing character separators, which can be included in list items by
5343 doubling, it is not possible to include a control character as data when it is
5344 set as the separator. Two such characters in succession are interpreted as
5345 enclosing an empty list item.
5349 .section "Empty items in lists" "SECTempitelis"
5350 .cindex "list" "empty item in"
5351 An empty item at the end of a list is always ignored. In other words, trailing
5352 separator characters are ignored. Thus, the list in
5354 senders = user@domain :
5356 contains only a single item. If you want to include an empty string as one item
5357 in a list, it must not be the last item. For example, this list contains three
5358 items, the second of which is empty:
5360 senders = user1@domain : : user2@domain
5362 &*Note*&: There must be white space between the two colons, as otherwise they
5363 are interpreted as representing a single colon data character (and the list
5364 would then contain just one item). If you want to specify a list that contains
5365 just one, empty item, you can do it as in this example:
5369 In this case, the first item is empty, and the second is discarded because it
5370 is at the end of the list.
5375 .section "Format of driver configurations" "SECTfordricon"
5376 .cindex "drivers" "configuration format"
5377 There are separate parts in the configuration for defining routers, transports,
5378 and authenticators. In each part, you are defining a number of driver
5379 instances, each with its own set of options. Each driver instance is defined by
5380 a sequence of lines like this:
5382 <&'instance name'&>:
5387 In the following example, the instance name is &(localuser)&, and it is
5388 followed by three options settings:
5393 transport = local_delivery
5395 For each driver instance, you specify which Exim code module it uses &-- by the
5396 setting of the &%driver%& option &-- and (optionally) some configuration
5397 settings. For example, in the case of transports, if you want a transport to
5398 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5399 a local file you would use the &(appendfile)& driver. Each of the drivers is
5400 described in detail in its own separate chapter later in this manual.
5402 You can have several routers, transports, or authenticators that are based on
5403 the same underlying driver (each must have a different instance name).
5405 The order in which routers are defined is important, because addresses are
5406 passed to individual routers one by one, in order. The order in which
5407 transports are defined does not matter at all. The order in which
5408 authenticators are defined is used only when Exim, as a client, is searching
5409 them to find one that matches an authentication mechanism offered by the
5412 .cindex "generic options"
5413 .cindex "options" "generic &-- definition of"
5414 Within a driver instance definition, there are two kinds of option: &'generic'&
5415 and &'private'&. The generic options are those that apply to all drivers of the
5416 same type (that is, all routers, all transports or all authenticators). The
5417 &%driver%& option is a generic option that must appear in every definition.
5418 .cindex "private options"
5419 The private options are special for each driver, and none need appear, because
5420 they all have default values.
5422 The options may appear in any order, except that the &%driver%& option must
5423 precede any private options, since these depend on the particular driver. For
5424 this reason, it is recommended that &%driver%& always be the first option.
5426 Driver instance names, which are used for reference in log entries and
5427 elsewhere, can be any sequence of letters, digits, and underscores (starting
5428 with a letter) and must be unique among drivers of the same type. A router and
5429 a transport (for example) can each have the same name, but no two router
5430 instances can have the same name. The name of a driver instance should not be
5431 confused with the name of the underlying driver module. For example, the
5432 configuration lines:
5437 create an instance of the &(smtp)& transport driver whose name is
5438 &(remote_smtp)&. The same driver code can be used more than once, with
5439 different instance names and different option settings each time. A second
5440 instance of the &(smtp)& transport, with different options, might be defined
5446 command_timeout = 10s
5448 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5449 these transport instances from routers, and these names would appear in log
5452 Comment lines may be present in the middle of driver specifications. The full
5453 list of option settings for any particular driver instance, including all the
5454 defaulted values, can be extracted by making use of the &%-bP%& command line
5462 . ////////////////////////////////////////////////////////////////////////////
5463 . ////////////////////////////////////////////////////////////////////////////
5465 .chapter "The default configuration file" "CHAPdefconfil"
5466 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5467 .cindex "default" "configuration file &""walk through""&"
5468 The default configuration file supplied with Exim as &_src/configure.default_&
5469 is sufficient for a host with simple mail requirements. As an introduction to
5470 the way Exim is configured, this chapter &"walks through"& the default
5471 configuration, giving brief explanations of the settings. Detailed descriptions
5472 of the options are given in subsequent chapters. The default configuration file
5473 itself contains extensive comments about ways you might want to modify the
5474 initial settings. However, note that there are many options that are not
5475 mentioned at all in the default configuration.
5479 .section "Main configuration settings" "SECTdefconfmain"
5480 The main (global) configuration option settings must always come first in the
5481 file. The first thing you'll see in the file, after some initial comments, is
5484 # primary_hostname =
5486 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5487 to know the official, fully qualified name of your host, and this is where you
5488 can specify it. However, in most cases you do not need to set this option. When
5489 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5491 The first three non-comment configuration lines are as follows:
5493 domainlist local_domains = @
5494 domainlist relay_to_domains =
5495 hostlist relay_from_hosts = 127.0.0.1
5497 These are not, in fact, option settings. They are definitions of two named
5498 domain lists and one named host list. Exim allows you to give names to lists of
5499 domains, hosts, and email addresses, in order to make it easier to manage the
5500 configuration file (see section &<<SECTnamedlists>>&).
5502 The first line defines a domain list called &'local_domains'&; this is used
5503 later in the configuration to identify domains that are to be delivered
5506 .cindex "@ in a domain list"
5507 There is just one item in this list, the string &"@"&. This is a special form
5508 of entry which means &"the name of the local host"&. Thus, if the local host is
5509 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5510 be delivered locally. Because the local host's name is referenced indirectly,
5511 the same configuration file can be used on different hosts.
5513 The second line defines a domain list called &'relay_to_domains'&, but the
5514 list itself is empty. Later in the configuration we will come to the part that
5515 controls mail relaying through the local host; it allows relaying to any
5516 domains in this list. By default, therefore, no relaying on the basis of a mail
5517 domain is permitted.
5519 The third line defines a host list called &'relay_from_hosts'&. This list is
5520 used later in the configuration to permit relaying from any host or IP address
5521 that matches the list. The default contains just the IP address of the IPv4
5522 loopback interface, which means that processes on the local host are able to
5523 submit mail for relaying by sending it over TCP/IP to that interface. No other
5524 hosts are permitted to submit messages for relaying.
5526 Just to be sure there's no misunderstanding: at this point in the configuration
5527 we aren't actually setting up any controls. We are just defining some domains
5528 and hosts that will be used in the controls that are specified later.
5530 The next two configuration lines are genuine option settings:
5532 acl_smtp_rcpt = acl_check_rcpt
5533 acl_smtp_data = acl_check_data
5535 These options specify &'Access Control Lists'& (ACLs) that are to be used
5536 during an incoming SMTP session for every recipient of a message (every RCPT
5537 command), and after the contents of the message have been received,
5538 respectively. The names of the lists are &'acl_check_rcpt'& and
5539 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5540 section of the configuration. The RCPT ACL controls which recipients are
5541 accepted for an incoming message &-- if a configuration does not provide an ACL
5542 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5543 contents of a message to be checked.
5545 Two commented-out option settings are next:
5547 # av_scanner = clamd:/tmp/clamd
5548 # spamd_address = 127.0.0.1 783
5550 These are example settings that can be used when Exim is compiled with the
5551 content-scanning extension. The first specifies the interface to the virus
5552 scanner, and the second specifies the interface to SpamAssassin. Further
5553 details are given in chapter &<<CHAPexiscan>>&.
5555 Three more commented-out option settings follow:
5557 # tls_advertise_hosts = *
5558 # tls_certificate = /etc/ssl/exim.crt
5559 # tls_privatekey = /etc/ssl/exim.pem
5561 These are example settings that can be used when Exim is compiled with
5562 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5563 first one specifies the list of clients that are allowed to use TLS when
5564 connecting to this server; in this case the wildcard means all clients. The
5565 other options specify where Exim should find its TLS certificate and private
5566 key, which together prove the server's identity to any clients that connect.
5567 More details are given in chapter &<<CHAPTLS>>&.
5569 Another two commented-out option settings follow:
5571 # daemon_smtp_ports = 25 : 465 : 587
5572 # tls_on_connect_ports = 465
5574 .cindex "port" "465 and 587"
5575 .cindex "port" "for message submission"
5576 .cindex "message" "submission, ports for"
5577 .cindex "ssmtp protocol"
5578 .cindex "smtps protocol"
5579 .cindex "SMTP" "ssmtp protocol"
5580 .cindex "SMTP" "smtps protocol"
5581 These options provide better support for roaming users who wish to use this
5582 server for message submission. They are not much use unless you have turned on
5583 TLS (as described in the previous paragraph) and authentication (about which
5584 more in section &<<SECTdefconfauth>>&). The usual SMTP port 25 is often blocked
5585 on end-user networks, so RFC 4409 specifies that message submission should use
5586 port 587 instead. However some software (notably Microsoft Outlook) cannot be
5587 configured to use port 587 correctly, so these settings also enable the
5588 non-standard &"smtps"& (aka &"ssmtp"&) port 465 (see section
5589 &<<SECTsupobssmt>>&).
5591 Two more commented-out options settings follow:
5594 # qualify_recipient =
5596 The first of these specifies a domain that Exim uses when it constructs a
5597 complete email address from a local login name. This is often needed when Exim
5598 receives a message from a local process. If you do not set &%qualify_domain%&,
5599 the value of &%primary_hostname%& is used. If you set both of these options,
5600 you can have different qualification domains for sender and recipient
5601 addresses. If you set only the first one, its value is used in both cases.
5603 .cindex "domain literal" "recognizing format"
5604 The following line must be uncommented if you want Exim to recognize
5605 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5606 (an IP address within square brackets) instead of a named domain.
5608 # allow_domain_literals
5610 The RFCs still require this form, but many people think that in the modern
5611 Internet it makes little sense to permit mail to be sent to specific hosts by
5612 quoting their IP addresses. This ancient format has been used by people who
5613 try to abuse hosts by using them for unwanted relaying. However, some
5614 people believe there are circumstances (for example, messages addressed to
5615 &'postmaster'&) where domain literals are still useful.
5617 The next configuration line is a kind of trigger guard:
5621 It specifies that no delivery must ever be run as the root user. The normal
5622 convention is to set up &'root'& as an alias for the system administrator. This
5623 setting is a guard against slips in the configuration.
5624 The list of users specified by &%never_users%& is not, however, the complete
5625 list; the build-time configuration in &_Local/Makefile_& has an option called
5626 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5627 contents of &%never_users%& are added to this list. By default
5628 FIXED_NEVER_USERS also specifies root.
5630 When a remote host connects to Exim in order to send mail, the only information
5631 Exim has about the host's identity is its IP address. The next configuration
5636 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5637 in order to get a host name. This improves the quality of the logging
5638 information, but if you feel it is too expensive, you can remove it entirely,
5639 or restrict the lookup to hosts on &"nearby"& networks.
5640 Note that it is not always possible to find a host name from an IP address,
5641 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5644 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5645 1413 (hence their names):
5648 rfc1413_query_timeout = 0s
5650 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5651 Few hosts offer RFC1413 service these days; calls have to be
5652 terminated by a timeout and this needlessly delays the startup
5653 of an incoming SMTP connection.
5654 If you have hosts for which you trust RFC1413 and need this
5655 information, you can change this.
5657 This line enables an efficiency SMTP option. It is negotiated by clients
5658 and not expected to cause problems but can be disabled if needed.
5663 When Exim receives messages over SMTP connections, it expects all addresses to
5664 be fully qualified with a domain, as required by the SMTP definition. However,
5665 if you are running a server to which simple clients submit messages, you may
5666 find that they send unqualified addresses. The two commented-out options:
5668 # sender_unqualified_hosts =
5669 # recipient_unqualified_hosts =
5671 show how you can specify hosts that are permitted to send unqualified sender
5672 and recipient addresses, respectively.
5674 The &%log_selector%& option is used to increase the detail of logging
5677 log_selector = +smtp_protocol_error +smtp_syntax_error \
5678 +tls_certificate_verified
5681 The &%percent_hack_domains%& option is also commented out:
5683 # percent_hack_domains =
5685 It provides a list of domains for which the &"percent hack"& is to operate.
5686 This is an almost obsolete form of explicit email routing. If you do not know
5687 anything about it, you can safely ignore this topic.
5689 The next two settings in the main part of the default configuration are
5690 concerned with messages that have been &"frozen"& on Exim's queue. When a
5691 message is frozen, Exim no longer continues to try to deliver it. Freezing
5692 occurs when a bounce message encounters a permanent failure because the sender
5693 address of the original message that caused the bounce is invalid, so the
5694 bounce cannot be delivered. This is probably the most common case, but there
5695 are also other conditions that cause freezing, and frozen messages are not
5696 always bounce messages.
5698 ignore_bounce_errors_after = 2d
5699 timeout_frozen_after = 7d
5701 The first of these options specifies that failing bounce messages are to be
5702 discarded after 2 days on the queue. The second specifies that any frozen
5703 message (whether a bounce message or not) is to be timed out (and discarded)
5704 after a week. In this configuration, the first setting ensures that no failing
5705 bounce message ever lasts a week.
5707 Exim queues it's messages in a spool directory. If you expect to have
5708 large queues, you may consider using this option. It splits the spool
5709 directory into subdirectories to avoid file system degradation from
5710 many files in a single directory, resulting in better performance.
5711 Manual manipulation of queued messages becomes more complex (though fortunately
5714 # split_spool_directory = true
5717 In an ideal world everybody follows the standards. For non-ASCII
5718 messages RFC 2047 is a standard, allowing a maximum line length of 76
5719 characters. Exim adheres that standard and won't process messages which
5720 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5721 In particular, the Exim maintainers have had multiple reports of
5722 problems from Russian administrators of issues until they disable this
5723 check, because of some popular, yet buggy, mail composition software.
5725 # check_rfc2047_length = false
5728 If you need to be strictly RFC compliant you may wish to disable the
5729 8BITMIME advertisement. Use this, if you exchange mails with systems
5730 that are not 8-bit clean.
5732 # accept_8bitmime = false
5735 Libraries you use may depend on specific environment settings. This
5736 imposes a security risk (e.g. PATH). There are two lists:
5737 &%keep_environment%& for the variables to import as they are, and
5738 &%add_environment%& for variables we want to set to a fixed value.
5739 Note that TZ is handled separately, by the $%timezone%$ runtime
5740 option and by the TIMEZONE_DEFAULT buildtime option.
5742 # keep_environment = ^LDAP
5743 # add_environment = PATH=/usr/bin::/bin
5747 .section "ACL configuration" "SECID54"
5748 .cindex "default" "ACLs"
5749 .cindex "&ACL;" "default configuration"
5750 In the default configuration, the ACL section follows the main configuration.
5751 It starts with the line
5755 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5756 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5757 and &%acl_smtp_data%& above.
5759 .cindex "RCPT" "ACL for"
5760 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5761 RCPT command specifies one of the message's recipients. The ACL statements
5762 are considered in order, until the recipient address is either accepted or
5763 rejected. The RCPT command is then accepted or rejected, according to the
5764 result of the ACL processing.
5768 This line, consisting of a name terminated by a colon, marks the start of the
5773 This ACL statement accepts the recipient if the sending host matches the list.
5774 But what does that strange list mean? It doesn't actually contain any host
5775 names or IP addresses. The presence of the colon puts an empty item in the
5776 list; Exim matches this only if the incoming message did not come from a remote
5777 host, because in that case, the remote hostname is empty. The colon is
5778 important. Without it, the list itself is empty, and can never match anything.
5780 What this statement is doing is to accept unconditionally all recipients in
5781 messages that are submitted by SMTP from local processes using the standard
5782 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5785 deny message = Restricted characters in address
5786 domains = +local_domains
5787 local_parts = ^[.] : ^.*[@%!/|]
5789 deny message = Restricted characters in address
5790 domains = !+local_domains
5791 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5793 These statements are concerned with local parts that contain any of the
5794 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5795 Although these characters are entirely legal in local parts (in the case of
5796 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5797 in Internet mail addresses.
5799 The first three have in the past been associated with explicitly routed
5800 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5801 option). Addresses containing these characters are regularly tried by spammers
5802 in an attempt to bypass relaying restrictions, and also by open relay testing
5803 programs. Unless you really need them it is safest to reject these characters
5804 at this early stage. This configuration is heavy-handed in rejecting these
5805 characters for all messages it accepts from remote hosts. This is a deliberate
5806 policy of being as safe as possible.
5808 The first rule above is stricter, and is applied to messages that are addressed
5809 to one of the local domains handled by this host. This is implemented by the
5810 first condition, which restricts it to domains that are listed in the
5811 &'local_domains'& domain list. The &"+"& character is used to indicate a
5812 reference to a named list. In this configuration, there is just one domain in
5813 &'local_domains'&, but in general there may be many.
5815 The second condition on the first statement uses two regular expressions to
5816 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5817 or &"|"&. If you have local accounts that include these characters, you will
5818 have to modify this rule.
5820 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5821 allows them because they have been encountered in practice. (Consider the
5822 common convention of local parts constructed as
5823 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5824 the author of Exim, who has no second initial.) However, a local part starting
5825 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5826 file name (for example, for a mailing list). This is also true for local parts
5827 that contain slashes. A pipe symbol can also be troublesome if the local part
5828 is incorporated unthinkingly into a shell command line.
5830 The second rule above applies to all other domains, and is less strict. This
5831 allows your own users to send outgoing messages to sites that use slashes
5832 and vertical bars in their local parts. It blocks local parts that begin
5833 with a dot, slash, or vertical bar, but allows these characters within the
5834 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5835 and &"!"& is blocked, as before. The motivation here is to prevent your users
5836 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5838 accept local_parts = postmaster
5839 domains = +local_domains
5841 This statement, which has two conditions, accepts an incoming address if the
5842 local part is &'postmaster'& and the domain is one of those listed in the
5843 &'local_domains'& domain list. The &"+"& character is used to indicate a
5844 reference to a named list. In this configuration, there is just one domain in
5845 &'local_domains'&, but in general there may be many.
5847 The presence of this statement means that mail to postmaster is never blocked
5848 by any of the subsequent tests. This can be helpful while sorting out problems
5849 in cases where the subsequent tests are incorrectly denying access.
5851 require verify = sender
5853 This statement requires the sender address to be verified before any subsequent
5854 ACL statement can be used. If verification fails, the incoming recipient
5855 address is refused. Verification consists of trying to route the address, to
5856 see if a bounce message could be delivered to it. In the case of remote
5857 addresses, basic verification checks only the domain, but &'callouts'& can be
5858 used for more verification if required. Section &<<SECTaddressverification>>&
5859 discusses the details of address verification.
5861 accept hosts = +relay_from_hosts
5862 control = submission
5864 This statement accepts the address if the message is coming from one of the
5865 hosts that are defined as being allowed to relay through this host. Recipient
5866 verification is omitted here, because in many cases the clients are dumb MUAs
5867 that do not cope well with SMTP error responses. For the same reason, the
5868 second line specifies &"submission mode"& for messages that are accepted. This
5869 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5870 messages that are deficient in some way, for example, because they lack a
5871 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5872 probably add recipient verification here, and disable submission mode.
5874 accept authenticated = *
5875 control = submission
5877 This statement accepts the address if the client host has authenticated itself.
5878 Submission mode is again specified, on the grounds that such messages are most
5879 likely to come from MUAs. The default configuration does not define any
5880 authenticators, though it does include some nearly complete commented-out
5881 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5882 fact authenticate until you complete the authenticator definitions.
5884 require message = relay not permitted
5885 domains = +local_domains : +relay_to_domains
5887 This statement rejects the address if its domain is neither a local domain nor
5888 one of the domains for which this host is a relay.
5890 require verify = recipient
5892 This statement requires the recipient address to be verified; if verification
5893 fails, the address is rejected.
5895 # deny message = rejected because $sender_host_address \
5896 # is in a black list at $dnslist_domain\n\
5898 # dnslists = black.list.example
5900 # warn dnslists = black.list.example
5901 # add_header = X-Warning: $sender_host_address is in \
5902 # a black list at $dnslist_domain
5903 # log_message = found in $dnslist_domain
5905 These commented-out lines are examples of how you could configure Exim to check
5906 sending hosts against a DNS black list. The first statement rejects messages
5907 from blacklisted hosts, whereas the second just inserts a warning header
5910 # require verify = csa
5912 This commented-out line is an example of how you could turn on client SMTP
5913 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5918 The final statement in the first ACL unconditionally accepts any recipient
5919 address that has successfully passed all the previous tests.
5923 This line marks the start of the second ACL, and names it. Most of the contents
5924 of this ACL are commented out:
5927 # message = This message contains a virus \
5930 These lines are examples of how to arrange for messages to be scanned for
5931 viruses when Exim has been compiled with the content-scanning extension, and a
5932 suitable virus scanner is installed. If the message is found to contain a
5933 virus, it is rejected with the given custom error message.
5935 # warn spam = nobody
5936 # message = X-Spam_score: $spam_score\n\
5937 # X-Spam_score_int: $spam_score_int\n\
5938 # X-Spam_bar: $spam_bar\n\
5939 # X-Spam_report: $spam_report
5941 These lines are an example of how to arrange for messages to be scanned by
5942 SpamAssassin when Exim has been compiled with the content-scanning extension,
5943 and SpamAssassin has been installed. The SpamAssassin check is run with
5944 &`nobody`& as its user parameter, and the results are added to the message as a
5945 series of extra header line. In this case, the message is not rejected,
5946 whatever the spam score.
5950 This final line in the DATA ACL accepts the message unconditionally.
5953 .section "Router configuration" "SECID55"
5954 .cindex "default" "routers"
5955 .cindex "routers" "default"
5956 The router configuration comes next in the default configuration, introduced
5961 Routers are the modules in Exim that make decisions about where to send
5962 messages. An address is passed to each router in turn, until it is either
5963 accepted, or failed. This means that the order in which you define the routers
5964 matters. Each router is fully described in its own chapter later in this
5965 manual. Here we give only brief overviews.
5968 # driver = ipliteral
5969 # domains = !+local_domains
5970 # transport = remote_smtp
5972 .cindex "domain literal" "default router"
5973 This router is commented out because the majority of sites do not want to
5974 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
5975 you uncomment this router, you also need to uncomment the setting of
5976 &%allow_domain_literals%& in the main part of the configuration.
5980 domains = ! +local_domains
5981 transport = remote_smtp
5982 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
5985 The first uncommented router handles addresses that do not involve any local
5986 domains. This is specified by the line
5988 domains = ! +local_domains
5990 The &%domains%& option lists the domains to which this router applies, but the
5991 exclamation mark is a negation sign, so the router is used only for domains
5992 that are not in the domain list called &'local_domains'& (which was defined at
5993 the start of the configuration). The plus sign before &'local_domains'&
5994 indicates that it is referring to a named list. Addresses in other domains are
5995 passed on to the following routers.
5997 The name of the router driver is &(dnslookup)&,
5998 and is specified by the &%driver%& option. Do not be confused by the fact that
5999 the name of this router instance is the same as the name of the driver. The
6000 instance name is arbitrary, but the name set in the &%driver%& option must be
6001 one of the driver modules that is in the Exim binary.
6003 The &(dnslookup)& router routes addresses by looking up their domains in the
6004 DNS in order to obtain a list of hosts to which the address is routed. If the
6005 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6006 specified by the &%transport%& option. If the router does not find the domain
6007 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6008 the address fails and is bounced.
6010 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6011 be entirely ignored. This option is present because a number of cases have been
6012 encountered where MX records in the DNS point to host names
6013 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6014 Completely ignoring these IP addresses causes Exim to fail to route the
6015 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6016 continue to try to deliver the message periodically until the address timed
6023 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6025 file_transport = address_file
6026 pipe_transport = address_pipe
6028 Control reaches this and subsequent routers only for addresses in the local
6029 domains. This router checks to see whether the local part is defined as an
6030 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6031 data that it looks up from that file. If no data is found for the local part,
6032 the value of the &%data%& option is empty, causing the address to be passed to
6035 &_/etc/aliases_& is a conventional name for the system aliases file that is
6036 often used. That is why it is referenced by from the default configuration
6037 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6038 &_Local/Makefile_& before building Exim.
6043 # local_part_suffix = +* : -*
6044 # local_part_suffix_optional
6045 file = $home/.forward
6050 file_transport = address_file
6051 pipe_transport = address_pipe
6052 reply_transport = address_reply
6054 This is the most complicated router in the default configuration. It is another
6055 redirection router, but this time it is looking for forwarding data set up by
6056 individual users. The &%check_local_user%& setting specifies a check that the
6057 local part of the address is the login name of a local user. If it is not, the
6058 router is skipped. The two commented options that follow &%check_local_user%&,
6061 # local_part_suffix = +* : -*
6062 # local_part_suffix_optional
6064 .vindex "&$local_part_suffix$&"
6065 show how you can specify the recognition of local part suffixes. If the first
6066 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6067 by any sequence of characters, is removed from the local part and placed in the
6068 variable &$local_part_suffix$&. The second suffix option specifies that the
6069 presence of a suffix in the local part is optional. When a suffix is present,
6070 the check for a local login uses the local part with the suffix removed.
6072 When a local user account is found, the file called &_.forward_& in the user's
6073 home directory is consulted. If it does not exist, or is empty, the router
6074 declines. Otherwise, the contents of &_.forward_& are interpreted as
6075 redirection data (see chapter &<<CHAPredirect>>& for more details).
6077 .cindex "Sieve filter" "enabling in default router"
6078 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6079 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6080 is commented out by default), the contents of the file are interpreted as a set
6081 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6082 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6083 separate document entitled &'Exim's interfaces to mail filtering'&.
6085 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6086 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6087 There are two reasons for doing this:
6090 Whether or not a local user has a &_.forward_& file is not really relevant when
6091 checking an address for validity; it makes sense not to waste resources doing
6094 More importantly, when Exim is verifying addresses or handling an EXPN
6095 command during an SMTP session, it is running as the Exim user, not as root.
6096 The group is the Exim group, and no additional groups are set up.
6097 It may therefore not be possible for Exim to read users' &_.forward_& files at
6101 The setting of &%check_ancestor%& prevents the router from generating a new
6102 address that is the same as any previous address that was redirected. (This
6103 works round a problem concerning a bad interaction between aliasing and
6104 forwarding &-- see section &<<SECTredlocmai>>&).
6106 The final three option settings specify the transports that are to be used when
6107 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6108 auto-reply, respectively. For example, if a &_.forward_& file contains
6110 a.nother@elsewhere.example, /home/spqr/archive
6112 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6118 # local_part_suffix = +* : -*
6119 # local_part_suffix_optional
6120 transport = local_delivery
6122 The final router sets up delivery into local mailboxes, provided that the local
6123 part is the name of a local login, by accepting the address and assigning it to
6124 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6125 routers, so the address is bounced. The commented suffix settings fulfil the
6126 same purpose as they do for the &(userforward)& router.
6129 .section "Transport configuration" "SECID56"
6130 .cindex "default" "transports"
6131 .cindex "transports" "default"
6132 Transports define mechanisms for actually delivering messages. They operate
6133 only when referenced from routers, so the order in which they are defined does
6134 not matter. The transports section of the configuration starts with
6138 One remote transport and four local transports are defined.
6144 This transport is used for delivering messages over SMTP connections.
6145 The list of remote hosts comes from the router.
6146 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6147 It is negotiated between client and server
6148 and not expected to cause problems but can be disabled if needed.
6149 All other options are defaulted.
6153 file = /var/mail/$local_part
6160 This &(appendfile)& transport is used for local delivery to user mailboxes in
6161 traditional BSD mailbox format. By default it runs under the uid and gid of the
6162 local user, which requires the sticky bit to be set on the &_/var/mail_&
6163 directory. Some systems use the alternative approach of running mail deliveries
6164 under a particular group instead of using the sticky bit. The commented options
6165 show how this can be done.
6167 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6168 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6169 similarly-named options above.
6175 This transport is used for handling deliveries to pipes that are generated by
6176 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6177 option specifies that any output on stdout or stderr generated by the pipe is to
6178 be returned to the sender.
6186 This transport is used for handling deliveries to files that are generated by
6187 redirection. The name of the file is not specified in this instance of
6188 &(appendfile)&, because it comes from the &(redirect)& router.
6193 This transport is used for handling automatic replies generated by users'
6198 .section "Default retry rule" "SECID57"
6199 .cindex "retry" "default rule"
6200 .cindex "default" "retry rule"
6201 The retry section of the configuration file contains rules which affect the way
6202 Exim retries deliveries that cannot be completed at the first attempt. It is
6203 introduced by the line
6207 In the default configuration, there is just one rule, which applies to all
6210 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6212 This causes any temporarily failing address to be retried every 15 minutes for
6213 2 hours, then at intervals starting at one hour and increasing by a factor of
6214 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6215 is not delivered after 4 days of temporary failure, it is bounced. The time is
6216 measured from first failure, not from the time the message was received.
6218 If the retry section is removed from the configuration, or is empty (that is,
6219 if no retry rules are defined), Exim will not retry deliveries. This turns
6220 temporary errors into permanent errors.
6223 .section "Rewriting configuration" "SECID58"
6224 The rewriting section of the configuration, introduced by
6228 contains rules for rewriting addresses in messages as they arrive. There are no
6229 rewriting rules in the default configuration file.
6233 .section "Authenticators configuration" "SECTdefconfauth"
6234 .cindex "AUTH" "configuration"
6235 The authenticators section of the configuration, introduced by
6237 begin authenticators
6239 defines mechanisms for the use of the SMTP AUTH command. The default
6240 configuration file contains two commented-out example authenticators
6241 which support plaintext username/password authentication using the
6242 standard PLAIN mechanism and the traditional but non-standard LOGIN
6243 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6244 to support most MUA software.
6246 The example PLAIN authenticator looks like this:
6249 # driver = plaintext
6250 # server_set_id = $auth2
6251 # server_prompts = :
6252 # server_condition = Authentication is not yet configured
6253 # server_advertise_condition = ${if def:tls_in_cipher }
6255 And the example LOGIN authenticator looks like this:
6258 # driver = plaintext
6259 # server_set_id = $auth1
6260 # server_prompts = <| Username: | Password:
6261 # server_condition = Authentication is not yet configured
6262 # server_advertise_condition = ${if def:tls_in_cipher }
6265 The &%server_set_id%& option makes Exim remember the authenticated username
6266 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6267 &%server_prompts%& option configures the &(plaintext)& authenticator so
6268 that it implements the details of the specific authentication mechanism,
6269 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6270 when Exim offers authentication to clients; in the examples, this is only
6271 when TLS or SSL has been started, so to enable the authenticators you also
6272 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6274 The &%server_condition%& setting defines how to verify that the username and
6275 password are correct. In the examples it just produces an error message.
6276 To make the authenticators work, you can use a string expansion
6277 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6279 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6280 usercode and password are in different positions.
6281 Chapter &<<CHAPplaintext>>& covers both.
6283 .ecindex IIDconfiwal
6287 . ////////////////////////////////////////////////////////////////////////////
6288 . ////////////////////////////////////////////////////////////////////////////
6290 .chapter "Regular expressions" "CHAPregexp"
6292 .cindex "regular expressions" "library"
6294 Exim supports the use of regular expressions in many of its options. It
6295 uses the PCRE regular expression library; this provides regular expression
6296 matching that is compatible with Perl 5. The syntax and semantics of
6297 regular expressions is discussed in
6298 online Perl manpages, in
6299 many Perl reference books, and also in
6300 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6301 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6303 The documentation for the syntax and semantics of the regular expressions that
6304 are supported by PCRE is included in the PCRE distribution, and no further
6305 description is included here. The PCRE functions are called from Exim using
6306 the default option settings (that is, with no PCRE options set), except that
6307 the PCRE_CASELESS option is set when the matching is required to be
6310 In most cases, when a regular expression is required in an Exim configuration,
6311 it has to start with a circumflex, in order to distinguish it from plain text
6312 or an &"ends with"& wildcard. In this example of a configuration setting, the
6313 second item in the colon-separated list is a regular expression.
6315 domains = a.b.c : ^\\d{3} : *.y.z : ...
6317 The doubling of the backslash is required because of string expansion that
6318 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6319 of this issue, and a way of avoiding the need for doubling backslashes. The
6320 regular expression that is eventually used in this example contains just one
6321 backslash. The circumflex is included in the regular expression, and has the
6322 normal effect of &"anchoring"& it to the start of the string that is being
6325 There are, however, two cases where a circumflex is not required for the
6326 recognition of a regular expression: these are the &%match%& condition in a
6327 string expansion, and the &%matches%& condition in an Exim filter file. In
6328 these cases, the relevant string is always treated as a regular expression; if
6329 it does not start with a circumflex, the expression is not anchored, and can
6330 match anywhere in the subject string.
6332 In all cases, if you want a regular expression to match at the end of a string,
6333 you must code the $ metacharacter to indicate this. For example:
6335 domains = ^\\d{3}\\.example
6337 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6340 domains = ^\\d{3}\\.example\$
6342 if you want &'example'& to be the top-level domain. The backslash before the
6343 $ is needed because string expansion also interprets dollar characters.
6347 . ////////////////////////////////////////////////////////////////////////////
6348 . ////////////////////////////////////////////////////////////////////////////
6350 .chapter "File and database lookups" "CHAPfdlookup"
6351 .scindex IIDfidalo1 "file" "lookups"
6352 .scindex IIDfidalo2 "database" "lookups"
6353 .cindex "lookup" "description of"
6354 Exim can be configured to look up data in files or databases as it processes
6355 messages. Two different kinds of syntax are used:
6358 A string that is to be expanded may contain explicit lookup requests. These
6359 cause parts of the string to be replaced by data that is obtained from the
6360 lookup. Lookups of this type are conditional expansion items. Different results
6361 can be defined for the cases of lookup success and failure. See chapter
6362 &<<CHAPexpand>>&, where string expansions are described in detail.
6363 The key for the lookup is specified as part of the string expansion.
6365 Lists of domains, hosts, and email addresses can contain lookup requests as a
6366 way of avoiding excessively long linear lists. In this case, the data that is
6367 returned by the lookup is often (but not always) discarded; whether the lookup
6368 succeeds or fails is what really counts. These kinds of list are described in
6369 chapter &<<CHAPdomhosaddlists>>&.
6370 The key for the lookup is given by the context in which the list is expanded.
6373 String expansions, lists, and lookups interact with each other in such a way
6374 that there is no order in which to describe any one of them that does not
6375 involve references to the others. Each of these three chapters makes more sense
6376 if you have read the other two first. If you are reading this for the first
6377 time, be aware that some of it will make a lot more sense after you have read
6378 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6380 .section "Examples of different lookup syntax" "SECID60"
6381 It is easy to confuse the two different kinds of lookup, especially as the
6382 lists that may contain the second kind are always expanded before being
6383 processed as lists. Therefore, they may also contain lookups of the first kind.
6384 Be careful to distinguish between the following two examples:
6386 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6387 domains = lsearch;/some/file
6389 The first uses a string expansion, the result of which must be a domain list.
6390 No strings have been specified for a successful or a failing lookup; the
6391 defaults in this case are the looked-up data and an empty string, respectively.
6392 The expansion takes place before the string is processed as a list, and the
6393 file that is searched could contain lines like this:
6395 192.168.3.4: domain1:domain2:...
6396 192.168.1.9: domain3:domain4:...
6398 When the lookup succeeds, the result of the expansion is a list of domains (and
6399 possibly other types of item that are allowed in domain lists).
6401 In the second example, the lookup is a single item in a domain list. It causes
6402 Exim to use a lookup to see if the domain that is being processed can be found
6403 in the file. The file could contains lines like this:
6408 Any data that follows the keys is not relevant when checking that the domain
6409 matches the list item.
6411 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6412 Consider a file containing lines like this:
6414 192.168.5.6: lsearch;/another/file
6416 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6417 first &%domains%& setting above generates the second setting, which therefore
6418 causes a second lookup to occur.
6420 The rest of this chapter describes the different lookup types that are
6421 available. Any of them can be used in any part of the configuration where a
6422 lookup is permitted.
6425 .section "Lookup types" "SECID61"
6426 .cindex "lookup" "types of"
6427 .cindex "single-key lookup" "definition of"
6428 Two different types of data lookup are implemented:
6431 The &'single-key'& type requires the specification of a file in which to look,
6432 and a single key to search for. The key must be a non-empty string for the
6433 lookup to succeed. The lookup type determines how the file is searched.
6435 .cindex "query-style lookup" "definition of"
6436 The &'query-style'& type accepts a generalized database query. No particular
6437 key value is assumed by Exim for query-style lookups. You can use whichever
6438 Exim variables you need to construct the database query.
6441 The code for each lookup type is in a separate source file that is included in
6442 the binary of Exim only if the corresponding compile-time option is set. The
6443 default settings in &_src/EDITME_& are:
6448 which means that only linear searching and DBM lookups are included by default.
6449 For some types of lookup (e.g. SQL databases), you need to install appropriate
6450 libraries and header files before building Exim.
6455 .section "Single-key lookup types" "SECTsinglekeylookups"
6456 .cindex "lookup" "single-key types"
6457 .cindex "single-key lookup" "list of types"
6458 The following single-key lookup types are implemented:
6461 .cindex "cdb" "description of"
6462 .cindex "lookup" "cdb"
6463 .cindex "binary zero" "in lookup key"
6464 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6465 string without a terminating binary zero. The cdb format is designed for
6466 indexed files that are read frequently and never updated, except by total
6467 re-creation. As such, it is particularly suitable for large files containing
6468 aliases or other indexed data referenced by an MTA. Information about cdb can
6469 be found in several places:
6471 &url(http://www.pobox.com/~djb/cdb.html)
6472 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6473 &url(http://packages.debian.org/stable/utils/freecdb.html)
6475 A cdb distribution is not needed in order to build Exim with cdb support,
6476 because the code for reading cdb files is included directly in Exim itself.
6477 However, no means of building or testing cdb files is provided with Exim, so
6478 you need to obtain a cdb distribution in order to do this.
6480 .cindex "DBM" "lookup type"
6481 .cindex "lookup" "dbm"
6482 .cindex "binary zero" "in lookup key"
6483 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6484 DBM file by looking up the record with the given key. A terminating binary
6485 zero is included in the key that is passed to the DBM library. See section
6486 &<<SECTdb>>& for a discussion of DBM libraries.
6488 .cindex "Berkeley DB library" "file format"
6489 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6490 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6491 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6492 the DB_UNKNOWN option. This enables it to handle any of the types of database
6493 that the library supports, and can be useful for accessing DBM files created by
6494 other applications. (For earlier DB versions, DB_HASH is always used.)
6496 .cindex "lookup" "dbmjz"
6497 .cindex "lookup" "dbm &-- embedded NULs"
6499 .cindex "dbmjz lookup type"
6500 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6501 interpreted as an Exim list; the elements of the list are joined together with
6502 ASCII NUL characters to form the lookup key. An example usage would be to
6503 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6504 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6505 &(cram_md5)& authenticator.
6507 .cindex "lookup" "dbmnz"
6508 .cindex "lookup" "dbm &-- terminating zero"
6509 .cindex "binary zero" "in lookup key"
6511 .cindex "&_/etc/userdbshadow.dat_&"
6512 .cindex "dbmnz lookup type"
6513 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6514 is not included in the key that is passed to the DBM library. You may need this
6515 if you want to look up data in files that are created by or shared with some
6516 other application that does not use terminating zeros. For example, you need to
6517 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6518 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6519 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6520 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6522 .cindex "lookup" "dsearch"
6523 .cindex "dsearch lookup type"
6524 &(dsearch)&: The given file must be a directory; this is searched for an entry
6525 whose name is the key by calling the &[lstat()]& function. The key may not
6526 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6527 the lookup is the name of the entry, which may be a file, directory,
6528 symbolic link, or any other kind of directory entry. An example of how this
6529 lookup can be used to support virtual domains is given in section
6530 &<<SECTvirtualdomains>>&.
6532 .cindex "lookup" "iplsearch"
6533 .cindex "iplsearch lookup type"
6534 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6535 terminated by a colon or white space or the end of the line. The keys in the
6536 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6537 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6538 being interpreted as a key terminator. For example:
6540 1.2.3.4: data for 1.2.3.4
6541 192.168.0.0/16: data for 192.168.0.0/16
6542 "abcd::cdab": data for abcd::cdab
6543 "abcd:abcd::/32" data for abcd:abcd::/32
6545 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6546 file is searched linearly, using the CIDR masks where present, until a matching
6547 key is found. The first key that matches is used; there is no attempt to find a
6548 &"best"& match. Apart from the way the keys are matched, the processing for
6549 &(iplsearch)& is the same as for &(lsearch)&.
6551 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6552 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6553 lookup types support only literal keys.
6555 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6556 the implicit key is the host's IP address rather than its name (see section
6557 &<<SECThoslispatsikey>>&).
6559 .cindex "linear search"
6560 .cindex "lookup" "lsearch"
6561 .cindex "lsearch lookup type"
6562 .cindex "case sensitivity" "in lsearch lookup"
6563 &(lsearch)&: The given file is a text file that is searched linearly for a
6564 line beginning with the search key, terminated by a colon or white space or the
6565 end of the line. The search is case-insensitive; that is, upper and lower case
6566 letters are treated as the same. The first occurrence of the key that is found
6567 in the file is used.
6569 White space between the key and the colon is permitted. The remainder of the
6570 line, with leading and trailing white space removed, is the data. This can be
6571 continued onto subsequent lines by starting them with any amount of white
6572 space, but only a single space character is included in the data at such a
6573 junction. If the data begins with a colon, the key must be terminated by a
6578 Empty lines and lines beginning with # are ignored, even if they occur in the
6579 middle of an item. This is the traditional textual format of alias files. Note
6580 that the keys in an &(lsearch)& file are literal strings. There is no
6581 wildcarding of any kind.
6583 .cindex "lookup" "lsearch &-- colons in keys"
6584 .cindex "white space" "in lsearch key"
6585 In most &(lsearch)& files, keys are not required to contain colons or #
6586 characters, or white space. However, if you need this feature, it is available.
6587 If a key begins with a doublequote character, it is terminated only by a
6588 matching quote (or end of line), and the normal escaping rules apply to its
6589 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6590 quoted keys (exactly as for unquoted keys). There is no special handling of
6591 quotes for the data part of an &(lsearch)& line.
6594 .cindex "NIS lookup type"
6595 .cindex "lookup" "NIS"
6596 .cindex "binary zero" "in lookup key"
6597 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6598 the given key, without a terminating binary zero. There is a variant called
6599 &(nis0)& which does include the terminating binary zero in the key. This is
6600 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6601 aliases; the full map names must be used.
6604 .cindex "wildlsearch lookup type"
6605 .cindex "lookup" "wildlsearch"
6606 .cindex "nwildlsearch lookup type"
6607 .cindex "lookup" "nwildlsearch"
6608 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6609 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6610 the file may be wildcarded. The difference between these two lookup types is
6611 that for &(wildlsearch)&, each key in the file is string-expanded before being
6612 used, whereas for &(nwildlsearch)&, no expansion takes place.
6614 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6615 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6616 file that are regular expressions can be made case-sensitive by the use of
6617 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6619 . ==== As this is a nested list, any displays it contains must be indented
6620 . ==== as otherwise they are too far to the left.
6623 The string may begin with an asterisk to mean &"ends with"&. For example:
6625 *.a.b.c data for anything.a.b.c
6626 *fish data for anythingfish
6629 The string may begin with a circumflex to indicate a regular expression. For
6630 example, for &(wildlsearch)&:
6632 ^\N\d+\.a\.b\N data for <digits>.a.b
6634 Note the use of &`\N`& to disable expansion of the contents of the regular
6635 expression. If you are using &(nwildlsearch)&, where the keys are not
6636 string-expanded, the equivalent entry is:
6638 ^\d+\.a\.b data for <digits>.a.b
6640 The case-insensitive flag is set at the start of compiling the regular
6641 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6642 For example, to make the entire pattern case-sensitive:
6644 ^(?-i)\d+\.a\.b data for <digits>.a.b
6647 If the regular expression contains white space or colon characters, you must
6648 either quote it (see &(lsearch)& above), or represent these characters in other
6649 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6650 colon. This may be easier than quoting, because if you quote, you have to
6651 escape all the backslashes inside the quotes.
6653 &*Note*&: It is not possible to capture substrings in a regular expression
6654 match for later use, because the results of all lookups are cached. If a lookup
6655 is repeated, the result is taken from the cache, and no actual pattern matching
6656 takes place. The values of all the numeric variables are unset after a
6657 &((n)wildlsearch)& match.
6660 Although I cannot see it being of much use, the general matching function that
6661 is used to implement &((n)wildlsearch)& means that the string may begin with a
6662 lookup name terminated by a semicolon, and followed by lookup data. For
6665 cdb;/some/file data for keys that match the file
6667 The data that is obtained from the nested lookup is discarded.
6670 Keys that do not match any of these patterns are interpreted literally. The
6671 continuation rules for the data are the same as for &(lsearch)&, and keys may
6672 be followed by optional colons.
6674 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6675 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6676 lookup types support only literal keys.
6680 .section "Query-style lookup types" "SECTquerystylelookups"
6681 .cindex "lookup" "query-style types"
6682 .cindex "query-style lookup" "list of types"
6683 The supported query-style lookup types are listed below. Further details about
6684 many of them are given in later sections.
6687 .cindex "DNS" "as a lookup type"
6688 .cindex "lookup" "DNS"
6689 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6690 are given in the supplied query. The resulting data is the contents of the
6691 records. See section &<<SECTdnsdb>>&.
6693 .cindex "InterBase lookup type"
6694 .cindex "lookup" "InterBase"
6695 &(ibase)&: This does a lookup in an InterBase database.
6697 .cindex "LDAP" "lookup type"
6698 .cindex "lookup" "LDAP"
6699 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6700 returns attributes from a single entry. There is a variant called &(ldapm)&
6701 that permits values from multiple entries to be returned. A third variant
6702 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6703 any attribute values. See section &<<SECTldap>>&.
6705 .cindex "MySQL" "lookup type"
6706 .cindex "lookup" "MySQL"
6707 &(mysql)&: The format of the query is an SQL statement that is passed to a
6708 MySQL database. See section &<<SECTsql>>&.
6710 .cindex "NIS+ lookup type"
6711 .cindex "lookup" "NIS+"
6712 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6713 the field to be returned. See section &<<SECTnisplus>>&.
6715 .cindex "Oracle" "lookup type"
6716 .cindex "lookup" "Oracle"
6717 &(oracle)&: The format of the query is an SQL statement that is passed to an
6718 Oracle database. See section &<<SECTsql>>&.
6720 .cindex "lookup" "passwd"
6721 .cindex "passwd lookup type"
6722 .cindex "&_/etc/passwd_&"
6723 &(passwd)& is a query-style lookup with queries that are just user names. The
6724 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6725 success, the result string is the same as you would get from an &(lsearch)&
6726 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6727 password value. For example:
6729 *:42:42:King Rat:/home/kr:/bin/bash
6732 .cindex "PostgreSQL lookup type"
6733 .cindex "lookup" "PostgreSQL"
6734 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6735 PostgreSQL database. See section &<<SECTsql>>&.
6738 .cindex "Redis lookup type"
6739 .cindex lookup Redis
6740 &(redis)&: The format of the query is either a simple get or simple set,
6741 passed to a Redis database. See section &<<SECTsql>>&.
6744 .cindex "sqlite lookup type"
6745 .cindex "lookup" "sqlite"
6746 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6747 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6750 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6751 not likely to be useful in normal operation.
6753 .cindex "whoson lookup type"
6754 .cindex "lookup" "whoson"
6755 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6756 allows a server to check whether a particular (dynamically allocated) IP
6757 address is currently allocated to a known (trusted) user and, optionally, to
6758 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6759 at one time for &"POP before SMTP"& authentication, but that approach has been
6760 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6761 &"POP before SMTP"& checking using ACL statements such as
6763 require condition = \
6764 ${lookup whoson {$sender_host_address}{yes}{no}}
6766 The query consists of a single IP address. The value returned is the name of
6767 the authenticated user, which is stored in the variable &$value$&. However, in
6768 this example, the data in &$value$& is not used; the result of the lookup is
6769 one of the fixed strings &"yes"& or &"no"&.
6774 .section "Temporary errors in lookups" "SECID63"
6775 .cindex "lookup" "temporary error in"
6776 Lookup functions can return temporary error codes if the lookup cannot be
6777 completed. For example, an SQL or LDAP database might be unavailable. For this
6778 reason, it is not advisable to use a lookup that might do this for critical
6779 options such as a list of local domains.
6781 When a lookup cannot be completed in a router or transport, delivery
6782 of the message (to the relevant address) is deferred, as for any other
6783 temporary error. In other circumstances Exim may assume the lookup has failed,
6784 or may give up altogether.
6788 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6789 .cindex "wildcard lookups"
6790 .cindex "lookup" "default values"
6791 .cindex "lookup" "wildcard"
6792 .cindex "lookup" "* added to type"
6793 .cindex "default" "in single-key lookups"
6794 In this context, a &"default value"& is a value specified by the administrator
6795 that is to be used if a lookup fails.
6797 &*Note:*& This section applies only to single-key lookups. For query-style
6798 lookups, the facilities of the query language must be used. An attempt to
6799 specify a default for a query-style lookup provokes an error.
6801 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6802 and the initial lookup fails, the key &"*"& is looked up in the file to
6803 provide a default value. See also the section on partial matching below.
6805 .cindex "*@ with single-key lookup"
6806 .cindex "lookup" "*@ added to type"
6807 .cindex "alias file" "per-domain default"
6808 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6809 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6810 character, a second lookup is done with everything before the last @ replaced
6811 by *. This makes it possible to provide per-domain defaults in alias files
6812 that include the domains in the keys. If the second lookup fails (or doesn't
6813 take place because there is no @ in the key), &"*"& is looked up.
6814 For example, a &(redirect)& router might contain:
6816 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6818 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6819 looks up these keys, in this order:
6825 The data is taken from whichever key it finds first. &*Note*&: In an
6826 &(lsearch)& file, this does not mean the first of these keys in the file. A
6827 complete scan is done for each key, and only if it is not found at all does
6828 Exim move on to try the next key.
6832 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6833 .cindex "partial matching"
6834 .cindex "wildcard lookups"
6835 .cindex "lookup" "partial matching"
6836 .cindex "lookup" "wildcard"
6837 .cindex "asterisk" "in search type"
6838 The normal operation of a single-key lookup is to search the file for an exact
6839 match with the given key. However, in a number of situations where domains are
6840 being looked up, it is useful to be able to do partial matching. In this case,
6841 information in the file that has a key starting with &"*."& is matched by any
6842 domain that ends with the components that follow the full stop. For example, if
6843 a key in a DBM file is
6845 *.dates.fict.example
6847 then when partial matching is enabled this is matched by (amongst others)
6848 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6849 by &'dates.fict.example'&, if that does not appear as a separate key in the
6852 &*Note*&: Partial matching is not available for query-style lookups. It is
6853 also not available for any lookup items in address lists (see section
6854 &<<SECTaddresslist>>&).
6856 Partial matching is implemented by doing a series of separate lookups using
6857 keys constructed by modifying the original subject key. This means that it can
6858 be used with any of the single-key lookup types, provided that
6859 partial matching keys
6860 beginning with a special prefix (default &"*."&) are included in the data file.
6861 Keys in the file that do not begin with the prefix are matched only by
6862 unmodified subject keys when partial matching is in use.
6864 Partial matching is requested by adding the string &"partial-"& to the front of
6865 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6866 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6867 is added at the start of the subject key, and it is looked up again. If that
6868 fails, further lookups are tried with dot-separated components removed from the
6869 start of the subject key, one-by-one, and &"*."& added on the front of what
6872 A minimum number of two non-* components are required. This can be adjusted
6873 by including a number before the hyphen in the search type. For example,
6874 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6875 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6876 subject key is &'2250.dates.fict.example'& then the following keys are looked
6877 up when the minimum number of non-* components is two:
6879 2250.dates.fict.example
6880 *.2250.dates.fict.example
6881 *.dates.fict.example
6884 As soon as one key in the sequence is successfully looked up, the lookup
6887 .cindex "lookup" "partial matching &-- changing prefix"
6888 .cindex "prefix" "for partial matching"
6889 The use of &"*."& as the partial matching prefix is a default that can be
6890 changed. The motivation for this feature is to allow Exim to operate with file
6891 formats that are used by other MTAs. A different prefix can be supplied in
6892 parentheses instead of the hyphen after &"partial"&. For example:
6894 domains = partial(.)lsearch;/some/file
6896 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6897 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6898 components is unchanged). The prefix may consist of any punctuation characters
6899 other than a closing parenthesis. It may be empty, for example:
6901 domains = partial1()cdb;/some/file
6903 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6904 &`a.b.c`&, &`b.c`&, and &`c`&.
6906 If &"partial0"& is specified, what happens at the end (when the lookup with
6907 just one non-wild component has failed, and the original key is shortened right
6908 down to the null string) depends on the prefix:
6911 If the prefix has zero length, the whole lookup fails.
6913 If the prefix has length 1, a lookup for just the prefix is done. For
6914 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6916 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6917 remainder is looked up. With the default prefix, therefore, the final lookup is
6918 for &"*"& on its own.
6920 Otherwise, the whole prefix is looked up.
6924 If the search type ends in &"*"& or &"*@"& (see section
6925 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6926 this implies happens after all partial lookups have failed. If &"partial0"& is
6927 specified, adding &"*"& to the search type has no effect with the default
6928 prefix, because the &"*"& key is already included in the sequence of partial
6929 lookups. However, there might be a use for lookup types such as
6930 &"partial0(.)lsearch*"&.
6932 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6933 in domain lists and the like. Partial matching works only in terms of
6934 dot-separated components; a key such as &`*fict.example`&
6935 in a database file is useless, because the asterisk in a partial matching
6936 subject key is always followed by a dot.
6941 .section "Lookup caching" "SECID64"
6942 .cindex "lookup" "caching"
6943 .cindex "caching" "lookup data"
6944 Exim caches all lookup results in order to avoid needless repetition of
6945 lookups. However, because (apart from the daemon) Exim operates as a collection
6946 of independent, short-lived processes, this caching applies only within a
6947 single Exim process. There is no inter-process lookup caching facility.
6949 For single-key lookups, Exim keeps the relevant files open in case there is
6950 another lookup that needs them. In some types of configuration this can lead to
6951 many files being kept open for messages with many recipients. To avoid hitting
6952 the operating system limit on the number of simultaneously open files, Exim
6953 closes the least recently used file when it needs to open more files than its
6954 own internal limit, which can be changed via the &%lookup_open_max%& option.
6956 The single-key lookup files are closed and the lookup caches are flushed at
6957 strategic points during delivery &-- for example, after all routing is
6963 .section "Quoting lookup data" "SECID65"
6964 .cindex "lookup" "quoting"
6965 .cindex "quoting" "in lookups"
6966 When data from an incoming message is included in a query-style lookup, there
6967 is the possibility of special characters in the data messing up the syntax of
6968 the query. For example, a NIS+ query that contains
6972 will be broken if the local part happens to contain a closing square bracket.
6973 For NIS+, data can be enclosed in double quotes like this:
6975 [name="$local_part"]
6977 but this still leaves the problem of a double quote in the data. The rule for
6978 NIS+ is that double quotes must be doubled. Other lookup types have different
6979 rules, and to cope with the differing requirements, an expansion operator
6980 of the following form is provided:
6982 ${quote_<lookup-type>:<string>}
6984 For example, the safest way to write the NIS+ query is
6986 [name="${quote_nisplus:$local_part}"]
6988 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
6989 operator can be used for all lookup types, but has no effect for single-key
6990 lookups, since no quoting is ever needed in their key strings.
6995 .section "More about dnsdb" "SECTdnsdb"
6996 .cindex "dnsdb lookup"
6997 .cindex "lookup" "dnsdb"
6998 .cindex "DNS" "as a lookup type"
6999 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7000 of a record type and a domain name, separated by an equals sign. For example,
7001 an expansion string could contain:
7003 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7005 If the lookup succeeds, the result is placed in &$value$&, which in this case
7006 is used on its own as the result. If the lookup does not succeed, the
7007 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7008 &<<SECTforexpfai>>& for an explanation of what this means.
7010 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7011 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7012 If no type is given, TXT is assumed.
7014 For any record type, if multiple records are found, the data is returned as a
7015 concatenation, with newline as the default separator. The order, of course,
7016 depends on the DNS resolver. You can specify a different separator character
7017 between multiple records by putting a right angle-bracket followed immediately
7018 by the new separator at the start of the query. For example:
7020 ${lookup dnsdb{>: a=host1.example}}
7022 It is permitted to specify a space as the separator character. Further
7023 white space is ignored.
7024 For lookup types that return multiple fields per record,
7025 an alternate field separator can be specified using a comma after the main
7026 separator character, followed immediately by the field separator.
7028 .cindex "PTR record" "in &(dnsdb)& lookup"
7029 When the type is PTR,
7030 the data can be an IP address, written as normal; inversion and the addition of
7031 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7033 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7035 If the data for a PTR record is not a syntactically valid IP address, it is not
7036 altered and nothing is added.
7038 .cindex "MX record" "in &(dnsdb)& lookup"
7039 .cindex "SRV record" "in &(dnsdb)& lookup"
7040 For an MX lookup, both the preference value and the host name are returned for
7041 each record, separated by a space. For an SRV lookup, the priority, weight,
7042 port, and host name are returned for each record, separated by spaces.
7043 The field separator can be modified as above.
7045 .cindex "TXT record" "in &(dnsdb)& lookup"
7046 .cindex "SPF record" "in &(dnsdb)& lookup"
7047 For TXT records with multiple items of data, only the first item is returned,
7048 unless a field separator is specified.
7049 To concatenate items without a separator, use a semicolon instead.
7051 default behaviour is to concatenate multiple items without using a separator.
7053 ${lookup dnsdb{>\n,: txt=a.b.example}}
7054 ${lookup dnsdb{>\n; txt=a.b.example}}
7055 ${lookup dnsdb{spf=example.org}}
7057 It is permitted to specify a space as the separator character. Further
7058 white space is ignored.
7060 .cindex "SOA record" "in &(dnsdb)& lookup"
7061 For an SOA lookup, while no result is obtained the lookup is redone with
7062 successively more leading components dropped from the given domain.
7063 Only the primary-nameserver field is returned unless a field separator is
7066 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7069 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7070 .cindex "dnsdb modifiers"
7071 .cindex "modifiers" "dnsdb"
7072 .cindex "options" "dnsdb"
7073 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7074 each followed by a comma,
7075 that may appear before the record type.
7077 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7078 temporary DNS error for any of them, the behaviour is controlled by
7079 a defer-option modifier.
7080 The possible keywords are
7081 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7082 With &"strict"& behaviour, any temporary DNS error causes the
7083 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7084 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7085 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7086 error causes the whole lookup to defer only if none of the other lookups
7087 succeed. The default is &"lax"&, so the following lookups are equivalent:
7089 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7090 ${lookup dnsdb{a=one.host.com:two.host.com}}
7092 Thus, in the default case, as long as at least one of the DNS lookups
7093 yields some data, the lookup succeeds.
7095 .cindex "DNSSEC" "dns lookup"
7096 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7097 The possible keywords are
7098 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7099 With &"strict"& or &"lax"& DNSSEC information is requested
7101 With &"strict"& a response from the DNS resolver that
7102 is not labelled as authenticated data
7103 is treated as equivalent to a temporary DNS error.
7104 The default is &"never"&.
7106 See also the &$lookup_dnssec_authenticated$& variable.
7108 .cindex timeout "dns lookup"
7109 .cindex "DNS" timeout
7110 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7111 The form is &"retrans_VAL"& where VAL is an Exim time specification
7113 The default value is set by the main configuration option &%dns_retrans%&.
7115 Retries for the dnsdb lookup can be controlled by a retry modifier.
7116 The form if &"retry_VAL"& where VAL is an integer.
7117 The default count is set by the main configuration option &%dns_retry%&.
7119 .cindex caching "of dns lookup"
7120 .cindex TTL "of dns lookup"
7122 Dnsdb lookup results are cached within a single process (and its children).
7123 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7124 value of the set of returned DNS records.
7127 .section "Pseudo dnsdb record types" "SECID66"
7128 .cindex "MX record" "in &(dnsdb)& lookup"
7129 By default, both the preference value and the host name are returned for
7130 each MX record, separated by a space. If you want only host names, you can use
7131 the pseudo-type MXH:
7133 ${lookup dnsdb{mxh=a.b.example}}
7135 In this case, the preference values are omitted, and just the host names are
7138 .cindex "name server for enclosing domain"
7139 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7140 records on the given domain, but if none are found, it removes the first
7141 component of the domain name, and tries again. This process continues until NS
7142 records are found or there are no more components left (or there is a DNS
7143 error). In other words, it may return the name servers for a top-level domain,
7144 but it never returns the root name servers. If there are no NS records for the
7145 top-level domain, the lookup fails. Consider these examples:
7147 ${lookup dnsdb{zns=xxx.quercite.com}}
7148 ${lookup dnsdb{zns=xxx.edu}}
7150 Assuming that in each case there are no NS records for the full domain name,
7151 the first returns the name servers for &%quercite.com%&, and the second returns
7152 the name servers for &%edu%&.
7154 You should be careful about how you use this lookup because, unless the
7155 top-level domain does not exist, the lookup always returns some host names. The
7156 sort of use to which this might be put is for seeing if the name servers for a
7157 given domain are on a blacklist. You can probably assume that the name servers
7158 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7161 .cindex "CSA" "in &(dnsdb)& lookup"
7162 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7163 records according to the CSA rules, which are described in section
7164 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7165 not sufficient because of the extra parent domain search behaviour of CSA. The
7166 result of a successful lookup such as:
7168 ${lookup dnsdb {csa=$sender_helo_name}}
7170 has two space-separated fields: an authorization code and a target host name.
7171 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7172 authorization required but absent, or &"?"& for unknown.
7174 .cindex "A+" "in &(dnsdb)& lookup"
7175 The pseudo-type A+ performs an AAAA
7176 and then an A lookup. All results are returned; defer processing
7177 (see below) is handled separately for each lookup. Example:
7179 ${lookup dnsdb {>; a+=$sender_helo_name}}
7183 .section "Multiple dnsdb lookups" "SECID67"
7184 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7185 However, you can specify a list of domains or IP addresses in a single
7186 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7187 the default separator, but with the ability to change this. For example:
7189 ${lookup dnsdb{one.domain.com:two.domain.com}}
7190 ${lookup dnsdb{a=one.host.com:two.host.com}}
7191 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7193 In order to retain backwards compatibility, there is one special case: if
7194 the lookup type is PTR and no change of separator is specified, Exim looks
7195 to see if the rest of the string is precisely one IPv6 address. In this
7196 case, it does not treat it as a list.
7198 The data from each lookup is concatenated, with newline separators by default,
7199 in the same way that multiple DNS records for a single item are handled. A
7200 different separator can be specified, as described above.
7205 .section "More about LDAP" "SECTldap"
7206 .cindex "LDAP" "lookup, more about"
7207 .cindex "lookup" "LDAP"
7208 .cindex "Solaris" "LDAP"
7209 The original LDAP implementation came from the University of Michigan; this has
7210 become &"Open LDAP"&, and there are now two different releases. Another
7211 implementation comes from Netscape, and Solaris 7 and subsequent releases
7212 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7213 the lookup function level, their error handling is different. For this reason
7214 it is necessary to set a compile-time variable when building Exim with LDAP, to
7215 indicate which LDAP library is in use. One of the following should appear in
7216 your &_Local/Makefile_&:
7218 LDAP_LIB_TYPE=UMICHIGAN
7219 LDAP_LIB_TYPE=OPENLDAP1
7220 LDAP_LIB_TYPE=OPENLDAP2
7221 LDAP_LIB_TYPE=NETSCAPE
7222 LDAP_LIB_TYPE=SOLARIS
7224 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7225 same interface as the University of Michigan version.
7227 There are three LDAP lookup types in Exim. These behave slightly differently in
7228 the way they handle the results of a query:
7231 &(ldap)& requires the result to contain just one entry; if there are more, it
7234 &(ldapdn)& also requires the result to contain just one entry, but it is the
7235 Distinguished Name that is returned rather than any attribute values.
7237 &(ldapm)& permits the result to contain more than one entry; the attributes
7238 from all of them are returned.
7242 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7243 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7244 the data returned by a successful lookup is described in the next section.
7245 First we explain how LDAP queries are coded.
7248 .section "Format of LDAP queries" "SECTforldaque"
7249 .cindex "LDAP" "query format"
7250 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7251 the configuration of a &(redirect)& router one might have this setting:
7253 data = ${lookup ldap \
7254 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7255 c=UK?mailbox?base?}}
7257 .cindex "LDAP" "with TLS"
7258 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7259 secure (encrypted) LDAP connections. The second of these ensures that an
7260 encrypted TLS connection is used.
7262 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7263 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7264 See the &%ldap_start_tls%& option.
7266 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7267 controlled. Every part of the TLS configuration can be configured by settings in
7268 &_exim.conf_&. Depending on the version of the client libraries installed on
7269 your system, some of the initialization may have required setting options in
7270 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7271 certificates. This revealed a nuance where the current UID that exim was
7272 running as could affect which config files it read. With Exim 4.83, these
7273 methods become optional, only taking effect if not specifically set in
7277 .section "LDAP quoting" "SECID68"
7278 .cindex "LDAP" "quoting"
7279 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7280 and the second because the LDAP query is represented as a URL. Furthermore,
7281 within an LDAP query, two different kinds of quoting are required. For this
7282 reason, there are two different LDAP-specific quoting operators.
7284 The &%quote_ldap%& operator is designed for use on strings that are part of
7285 filter specifications. Conceptually, it first does the following conversions on
7293 in accordance with RFC 2254. The resulting string is then quoted according
7294 to the rules for URLs, that is, all non-alphanumeric characters except
7298 are converted to their hex values, preceded by a percent sign. For example:
7300 ${quote_ldap: a(bc)*, a<yz>; }
7304 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7306 Removing the URL quoting, this is (with a leading and a trailing space):
7308 a\28bc\29\2A, a<yz>;
7310 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7311 base DN specifications in queries. Conceptually, it first converts the string
7312 by inserting a backslash in front of any of the following characters:
7316 It also inserts a backslash before any leading spaces or # characters, and
7317 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7318 is then quoted according to the rules for URLs. For example:
7320 ${quote_ldap_dn: a(bc)*, a<yz>; }
7324 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7326 Removing the URL quoting, this is (with a trailing space):
7328 \ a(bc)*\, a\<yz\>\;\
7330 There are some further comments about quoting in the section on LDAP
7331 authentication below.
7334 .section "LDAP connections" "SECID69"
7335 .cindex "LDAP" "connections"
7336 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7337 is in use, via a Unix domain socket. The example given above does not specify
7338 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7341 ldap://<hostname>:<port>/...
7343 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7344 used. When no server is specified in a query, a list of default servers is
7345 taken from the &%ldap_default_servers%& configuration option. This supplies a
7346 colon-separated list of servers which are tried in turn until one successfully
7347 handles a query, or there is a serious error. Successful handling either
7348 returns the requested data, or indicates that it does not exist. Serious errors
7349 are syntactical, or multiple values when only a single value is expected.
7350 Errors which cause the next server to be tried are connection failures, bind
7351 failures, and timeouts.
7353 For each server name in the list, a port number can be given. The standard way
7354 of specifying a host and port is to use a colon separator (RFC 1738). Because
7355 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7356 doubled. For example
7358 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7360 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7361 to the LDAP library with no server name, and the library's default (normally
7362 the local host) is used.
7364 If you are using the OpenLDAP library, you can connect to an LDAP server using
7365 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7366 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7367 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7370 For this type of connection, instead of a host name for the server, a pathname
7371 for the socket is required, and the port number is not relevant. The pathname
7372 can be specified either as an item in &%ldap_default_servers%&, or inline in
7373 the query. In the former case, you can have settings such as
7375 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7377 When the pathname is given in the query, you have to escape the slashes as
7378 &`%2F`& to fit in with the LDAP URL syntax. For example:
7380 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7382 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7383 a pathname, it uses the Unix domain socket code, even if the query actually
7384 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7385 socket connection. This behaviour means that you can use a setting of
7386 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7387 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7388 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7391 If an explicit &`ldapi`& type is given in a query when a host name is
7392 specified, an error is diagnosed. However, if there are more items in
7393 &%ldap_default_servers%&, they are tried. In other words:
7396 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7399 Using &`ldapi`& with a host name causes an error.
7403 Using &`ldapi`& with no host or path in the query, and no setting of
7404 &%ldap_default_servers%&, does whatever the library does by default.
7408 .section "LDAP authentication and control information" "SECID70"
7409 .cindex "LDAP" "authentication"
7410 The LDAP URL syntax provides no way of passing authentication and other control
7411 information to the server. To make this possible, the URL in an LDAP query may
7412 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7413 spaces. If a value contains spaces it must be enclosed in double quotes, and
7414 when double quotes are used, backslash is interpreted in the usual way inside
7415 them. The following names are recognized:
7417 &`DEREFERENCE`& set the dereferencing parameter
7418 &`NETTIME `& set a timeout for a network operation
7419 &`USER `& set the DN, for authenticating the LDAP bind
7420 &`PASS `& set the password, likewise
7421 &`REFERRALS `& set the referrals parameter
7422 &`SERVERS `& set alternate server list for this query only
7423 &`SIZE `& set the limit for the number of entries returned
7424 &`TIME `& set the maximum waiting time for a query
7426 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7427 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7428 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7429 library from trying to follow referrals issued by the LDAP server.
7431 .cindex LDAP timeout
7432 .cindex timeout "LDAP lookup"
7433 The name CONNECT is an obsolete name for NETTIME, retained for
7434 backwards compatibility. This timeout (specified as a number of seconds) is
7435 enforced from the client end for operations that can be carried out over a
7436 network. Specifically, it applies to network connections and calls to the
7437 &'ldap_result()'& function. If the value is greater than zero, it is used if
7438 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7439 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7440 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7441 Netscape SDK; for OpenLDAP no action is taken.
7443 The TIME parameter (also a number of seconds) is passed to the server to
7444 set a server-side limit on the time taken to complete a search.
7446 The SERVERS parameter allows you to specify an alternate list of ldap servers
7447 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7448 default list of ldap servers, and a single lookup can specify a single ldap
7449 server to use. But when you need to do a lookup with a list of servers that is
7450 different than the default list (maybe different order, maybe a completely
7451 different set of servers), the SERVERS parameter allows you to specify this
7452 alternate list (colon-separated).
7454 Here is an example of an LDAP query in an Exim lookup that uses some of these
7455 values. This is a single line, folded to fit on the page:
7458 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7459 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7462 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7463 any of the auxiliary data. Exim configuration settings that include lookups
7464 which contain password information should be preceded by &"hide"& to prevent
7465 non-admin users from using the &%-bP%& option to see their values.
7467 The auxiliary data items may be given in any order. The default is no
7468 connection timeout (the system timeout is used), no user or password, no limit
7469 on the number of entries returned, and no time limit on queries.
7471 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7472 removes any URL quoting that it may contain before passing it LDAP. Apparently
7473 some libraries do this for themselves, but some do not. Removing the URL
7474 quoting has two advantages:
7477 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7478 DNs as with DNs inside actual queries.
7480 It permits spaces inside USER= DNs.
7483 For example, a setting such as
7485 USER=cn=${quote_ldap_dn:$1}
7487 should work even if &$1$& contains spaces.
7489 Expanded data for the PASS= value should be quoted using the &%quote%&
7490 expansion operator, rather than the LDAP quote operators. The only reason this
7491 field needs quoting is to ensure that it conforms to the Exim syntax, which
7492 does not allow unquoted spaces. For example:
7496 The LDAP authentication mechanism can be used to check passwords as part of
7497 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7502 .section "Format of data returned by LDAP" "SECID71"
7503 .cindex "LDAP" "returned data formats"
7504 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7505 as a sequence of values, for example
7507 cn=manager,o=University of Cambridge,c=UK
7509 The &(ldap)& lookup type generates an error if more than one entry matches the
7510 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7511 the result between the data from different entries. It is possible for multiple
7512 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7513 you know that whatever values are returned all came from a single entry in the
7516 In the common case where you specify a single attribute in your LDAP query, the
7517 result is not quoted, and does not contain the attribute name. If the attribute
7518 has multiple values, they are separated by commas. Any comma that is
7519 part of an attribute's value is doubled.
7521 If you specify multiple attributes, the result contains space-separated, quoted
7522 strings, each preceded by the attribute name and an equals sign. Within the
7523 quotes, the quote character, backslash, and newline are escaped with
7524 backslashes, and commas are used to separate multiple values for the attribute.
7525 Any commas in attribute values are doubled
7526 (permitting treatment of the values as a comma-separated list).
7527 Apart from the escaping, the string within quotes takes the same form as the
7528 output when a single attribute is requested. Specifying no attributes is the
7529 same as specifying all of an entry's attributes.
7531 Here are some examples of the output format. The first line of each pair is an
7532 LDAP query, and the second is the data that is returned. The attribute called
7533 &%attr1%& has two values, one of them with an embedded comma, whereas
7534 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7535 (they have SUP &%attr%& in their schema definitions).
7538 ldap:///o=base?attr1?sub?(uid=fred)
7541 ldap:///o=base?attr2?sub?(uid=fred)
7544 ldap:///o=base?attr?sub?(uid=fred)
7545 value1.1,value1,,2,value two
7547 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7548 attr1="value1.1,value1,,2" attr2="value two"
7550 ldap:///o=base??sub?(uid=fred)
7551 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7554 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7555 results of LDAP lookups.
7556 The &%extract%& operator in string expansions can be used to pick out
7557 individual fields from data that consists of &'key'&=&'value'& pairs.
7558 The &%listextract%& operator should be used to pick out individual values
7559 of attributes, even when only a single value is expected.
7560 The doubling of embedded commas allows you to use the returned data as a
7561 comma separated list (using the "<," syntax for changing the input list separator).
7566 .section "More about NIS+" "SECTnisplus"
7567 .cindex "NIS+ lookup type"
7568 .cindex "lookup" "NIS+"
7569 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7570 and field name. If this is given, the result of a successful query is the
7571 contents of the named field; otherwise the result consists of a concatenation
7572 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7573 values containing spaces are quoted. For example, the query
7575 [name=mg1456],passwd.org_dir
7577 might return the string
7579 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7580 home=/home/mg1456 shell=/bin/bash shadow=""
7582 (split over two lines here to fit on the page), whereas
7584 [name=mg1456],passwd.org_dir:gcos
7590 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7591 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7592 operator is to double any quote characters within the text.
7596 .section "SQL lookups" "SECTsql"
7597 .cindex "SQL lookup types"
7598 .cindex "MySQL" "lookup type"
7599 .cindex "PostgreSQL lookup type"
7600 .cindex "lookup" "MySQL"
7601 .cindex "lookup" "PostgreSQL"
7602 .cindex "Oracle" "lookup type"
7603 .cindex "lookup" "Oracle"
7604 .cindex "InterBase lookup type"
7605 .cindex "lookup" "InterBase"
7606 .cindex "Redis lookup type"
7607 .cindex lookup Redis
7608 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7610 databases. Queries for these databases contain SQL statements, so an example
7613 ${lookup mysql{select mailbox from users where id='userx'}\
7616 If the result of the query contains more than one field, the data for each
7617 field in the row is returned, preceded by its name, so the result of
7619 ${lookup pgsql{select home,name from users where id='userx'}\
7624 home=/home/userx name="Mister X"
7626 Empty values and values containing spaces are double quoted, with embedded
7627 quotes escaped by a backslash. If the result of the query contains just one
7628 field, the value is passed back verbatim, without a field name, for example:
7632 If the result of the query yields more than one row, it is all concatenated,
7633 with a newline between the data for each row.
7636 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7637 .cindex "MySQL" "lookup type"
7638 .cindex "PostgreSQL lookup type"
7639 .cindex "lookup" "MySQL"
7640 .cindex "lookup" "PostgreSQL"
7641 .cindex "Oracle" "lookup type"
7642 .cindex "lookup" "Oracle"
7643 .cindex "InterBase lookup type"
7644 .cindex "lookup" "InterBase"
7645 .cindex "Redis lookup type"
7646 .cindex lookup Redis
7647 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7648 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7649 or &%redis_servers%&
7650 option (as appropriate) must be set to a colon-separated list of server
7652 (For MySQL and PostgreSQL, the global option need not be set if all
7653 queries contain their own server information &-- see section
7654 &<<SECTspeserque>>&.)
7656 each item in the list is a slash-separated list of four
7657 items: host name, database name, user name, and password. In the case of
7658 Oracle, the host name field is used for the &"service name"&, and the database
7659 name field is not used and should be empty. For example:
7661 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7663 Because password data is sensitive, you should always precede the setting with
7664 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7665 option. Here is an example where two MySQL servers are listed:
7667 hide mysql_servers = localhost/users/root/secret:\
7668 otherhost/users/root/othersecret
7670 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7671 because this is a colon-separated list, the colon has to be doubled. For each
7672 query, these parameter groups are tried in order until a connection is made and
7673 a query is successfully processed. The result of a query may be that no data is
7674 found, but that is still a successful query. In other words, the list of
7675 servers provides a backup facility, not a list of different places to look.
7677 For Redis the global option need not be specified if all queries contain their
7678 own server information &-- see section &<<SECTspeserque>>&.
7679 If specified, the option must be set to a colon-separated list of server
7681 Each item in the list is a slash-separated list of three items:
7682 host, database number, and password.
7684 The host is required and may be either an IPv4 address and optional
7685 port number (separated by a colon, which needs doubling due to the
7686 higher-level list), or a Unix socket pathname enclosed in parentheses
7688 The database number is optional; if present that number is selected in the backend
7690 The password is optional; if present it is used to authenticate to the backend
7693 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7694 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7695 respectively, and the characters single-quote, double-quote, and backslash
7696 itself are escaped with backslashes.
7698 The &%quote_redis%& expansion operator
7699 escapes whitespace and backslash characters with a backslash.
7701 .section "Specifying the server in the query" "SECTspeserque"
7702 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7703 it is possible to specify a list of servers with an individual query. This is
7704 done by starting the query with
7706 &`servers=`&&'server1:server2:server3:...'&&`;`&
7708 Each item in the list may take one of two forms:
7710 If it contains no slashes it is assumed to be just a host name. The appropriate
7711 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7712 of the same name, and the remaining parameters (database, user, password) are
7715 If it contains any slashes, it is taken as a complete parameter set.
7717 The list of servers is used in exactly the same way as the global list.
7718 Once a connection to a server has happened and a query has been
7719 successfully executed, processing of the lookup ceases.
7721 This feature is intended for use in master/slave situations where updates
7722 are occurring and you want to update the master rather than a slave. If the
7723 master is in the list as a backup for reading, you might have a global setting
7726 mysql_servers = slave1/db/name/pw:\
7730 In an updating lookup, you could then write:
7732 ${lookup mysql{servers=master; UPDATE ...} }
7734 That query would then be sent only to the master server. If, on the other hand,
7735 the master is not to be used for reading, and so is not present in the global
7736 option, you can still update it by a query of this form:
7738 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7742 .section "Special MySQL features" "SECID73"
7743 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7744 causes a connection to the server on the local host by means of a Unix domain
7745 socket. An alternate socket can be specified in parentheses.
7746 An option group name for MySQL option files can be specified in square brackets;
7747 the default value is &"exim"&.
7748 The full syntax of each item in &%mysql_servers%& is:
7750 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7751 <&'database'&>/<&'user'&>/<&'password'&>
7753 Any of the four sub-parts of the first field can be omitted. For normal use on
7754 the local host it can be left blank or set to just &"localhost"&.
7756 No database need be supplied &-- but if it is absent here, it must be given in
7759 If a MySQL query is issued that does not request any data (an insert, update,
7760 or delete command), the result of the lookup is the number of rows affected.
7762 &*Warning*&: This can be misleading. If an update does not actually change
7763 anything (for example, setting a field to the value it already has), the result
7764 is zero because no rows are affected.
7767 .section "Special PostgreSQL features" "SECID74"
7768 PostgreSQL lookups can also use Unix domain socket connections to the database.
7769 This is usually faster and costs less CPU time than a TCP/IP connection.
7770 However it can be used only if the mail server runs on the same machine as the
7771 database server. A configuration line for PostgreSQL via Unix domain sockets
7774 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7776 In other words, instead of supplying a host name, a path to the socket is
7777 given. The path name is enclosed in parentheses so that its slashes aren't
7778 visually confused with the delimiters for the other server parameters.
7780 If a PostgreSQL query is issued that does not request any data (an insert,
7781 update, or delete command), the result of the lookup is the number of rows
7784 .section "More about SQLite" "SECTsqlite"
7785 .cindex "lookup" "SQLite"
7786 .cindex "sqlite lookup type"
7787 SQLite is different to the other SQL lookups because a file name is required in
7788 addition to the SQL query. An SQLite database is a single file, and there is no
7789 daemon as in the other SQL databases. The interface to Exim requires the name
7790 of the file, as an absolute path, to be given at the start of the query. It is
7791 separated from the query by white space. This means that the path name cannot
7792 contain white space. Here is a lookup expansion example:
7794 ${lookup sqlite {/some/thing/sqlitedb \
7795 select name from aliases where id='userx';}}
7797 In a list, the syntax is similar. For example:
7799 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7800 select * from relays where ip='$sender_host_address';
7802 The only character affected by the &%quote_sqlite%& operator is a single
7803 quote, which it doubles.
7805 .cindex timeout SQLite
7806 .cindex sqlite "lookup timeout"
7807 The SQLite library handles multiple simultaneous accesses to the database
7808 internally. Multiple readers are permitted, but only one process can
7809 update at once. Attempts to access the database while it is being updated
7810 are rejected after a timeout period, during which the SQLite library
7811 waits for the lock to be released. In Exim, the default timeout is set
7812 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7815 .section "More about Redis" "SECTredis"
7816 .cindex "lookup" "Redis"
7817 .cindex "redis lookup type"
7818 Redis is a non-SQL database. Commands are simple get and set.
7821 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
7822 ${lookup redis{get keyname}}
7829 . ////////////////////////////////////////////////////////////////////////////
7830 . ////////////////////////////////////////////////////////////////////////////
7832 .chapter "Domain, host, address, and local part lists" &&&
7833 "CHAPdomhosaddlists" &&&
7834 "Domain, host, and address lists"
7835 .scindex IIDdohoadli "lists of domains; hosts; etc."
7836 A number of Exim configuration options contain lists of domains, hosts,
7837 email addresses, or local parts. For example, the &%hold_domains%& option
7838 contains a list of domains whose delivery is currently suspended. These lists
7839 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7840 arguments to expansion conditions such as &%match_domain%&.
7842 Each item in one of these lists is a pattern to be matched against a domain,
7843 host, email address, or local part, respectively. In the sections below, the
7844 different types of pattern for each case are described, but first we cover some
7845 general facilities that apply to all four kinds of list.
7847 Note that other parts of Exim use a &'string list'& which does not
7848 support all the complexity available in
7849 domain, host, address and local part lists.
7853 .section "Expansion of lists" "SECTlistexpand"
7854 .cindex "expansion" "of lists"
7855 Each list is expanded as a single string before it is used.
7857 &'Exception: the router headers_remove option, where list-item
7858 splitting is done before string-expansion.'&
7861 expansion must be a list, possibly containing empty items, which is split up
7862 into separate items for matching. By default, colon is the separator character,
7863 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7864 &<<SECTempitelis>>& for details of the list syntax; the second of these
7865 discusses the way to specify empty list items.
7868 If the string expansion is forced to fail, Exim behaves as if the item it is
7869 testing (domain, host, address, or local part) is not in the list. Other
7870 expansion failures cause temporary errors.
7872 If an item in a list is a regular expression, backslashes, dollars and possibly
7873 other special characters in the expression must be protected against
7874 misinterpretation by the string expander. The easiest way to do this is to use
7875 the &`\N`& expansion feature to indicate that the contents of the regular
7876 expression should not be expanded. For example, in an ACL you might have:
7878 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7879 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7881 The first item is a regular expression that is protected from expansion by
7882 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7883 senders based on the receiving domain.
7888 .section "Negated items in lists" "SECID76"
7889 .cindex "list" "negation"
7890 .cindex "negation" "in lists"
7891 Items in a list may be positive or negative. Negative items are indicated by a
7892 leading exclamation mark, which may be followed by optional white space. A list
7893 defines a set of items (domains, etc). When Exim processes one of these lists,
7894 it is trying to find out whether a domain, host, address, or local part
7895 (respectively) is in the set that is defined by the list. It works like this:
7897 The list is scanned from left to right. If a positive item is matched, the
7898 subject that is being checked is in the set; if a negative item is matched, the
7899 subject is not in the set. If the end of the list is reached without the
7900 subject having matched any of the patterns, it is in the set if the last item
7901 was a negative one, but not if it was a positive one. For example, the list in
7903 domainlist relay_to_domains = !a.b.c : *.b.c
7905 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7906 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7907 list is positive. However, if the setting were
7909 domainlist relay_to_domains = !a.b.c
7911 then all domains other than &'a.b.c'& would match because the last item in the
7912 list is negative. In other words, a list that ends with a negative item behaves
7913 as if it had an extra item &`:*`& on the end.
7915 Another way of thinking about positive and negative items in lists is to read
7916 the connector as &"or"& after a positive item and as &"and"& after a negative
7921 .section "File names in lists" "SECTfilnamlis"
7922 .cindex "list" "file name in"
7923 If an item in a domain, host, address, or local part list is an absolute file
7924 name (beginning with a slash character), each line of the file is read and
7925 processed as if it were an independent item in the list, except that further
7926 file names are not allowed,
7927 and no expansion of the data from the file takes place.
7928 Empty lines in the file are ignored, and the file may also contain comment
7932 For domain and host lists, if a # character appears anywhere in a line of the
7933 file, it and all following characters are ignored.
7935 Because local parts may legitimately contain # characters, a comment in an
7936 address list or local part list file is recognized only if # is preceded by
7937 white space or the start of the line. For example:
7939 not#comment@x.y.z # but this is a comment
7943 Putting a file name in a list has the same effect as inserting each line of the
7944 file as an item in the list (blank lines and comments excepted). However, there
7945 is one important difference: the file is read each time the list is processed,
7946 so if its contents vary over time, Exim's behaviour changes.
7948 If a file name is preceded by an exclamation mark, the sense of any match
7949 within the file is inverted. For example, if
7951 hold_domains = !/etc/nohold-domains
7953 and the file contains the lines
7958 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7959 any domain matching &`*.b.c`& is not.
7963 .section "An lsearch file is not an out-of-line list" "SECID77"
7964 As will be described in the sections that follow, lookups can be used in lists
7965 to provide indexed methods of checking list membership. There has been some
7966 confusion about the way &(lsearch)& lookups work in lists. Because
7967 an &(lsearch)& file contains plain text and is scanned sequentially, it is
7968 sometimes thought that it is allowed to contain wild cards and other kinds of
7969 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
7970 always fixed strings, just as for any other single-key lookup type.
7972 If you want to use a file to contain wild-card patterns that form part of a
7973 list, just give the file name on its own, without a search type, as described
7974 in the previous section. You could also use the &(wildlsearch)& or
7975 &(nwildlsearch)&, but there is no advantage in doing this.
7980 .section "Named lists" "SECTnamedlists"
7981 .cindex "named lists"
7982 .cindex "list" "named"
7983 A list of domains, hosts, email addresses, or local parts can be given a name
7984 which is then used to refer to the list elsewhere in the configuration. This is
7985 particularly convenient if the same list is required in several different
7986 places. It also allows lists to be given meaningful names, which can improve
7987 the readability of the configuration. For example, it is conventional to define
7988 a domain list called &'local_domains'& for all the domains that are handled
7989 locally on a host, using a configuration line such as
7991 domainlist local_domains = localhost:my.dom.example
7993 Named lists are referenced by giving their name preceded by a plus sign, so,
7994 for example, a router that is intended to handle local domains would be
7995 configured with the line
7997 domains = +local_domains
7999 The first router in a configuration is often one that handles all domains
8000 except the local ones, using a configuration with a negated item like this:
8004 domains = ! +local_domains
8005 transport = remote_smtp
8008 The four kinds of named list are created by configuration lines starting with
8009 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8010 respectively. Then there follows the name that you are defining, followed by an
8011 equals sign and the list itself. For example:
8013 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8014 addresslist bad_senders = cdb;/etc/badsenders
8016 A named list may refer to other named lists:
8018 domainlist dom1 = first.example : second.example
8019 domainlist dom2 = +dom1 : third.example
8020 domainlist dom3 = fourth.example : +dom2 : fifth.example
8022 &*Warning*&: If the last item in a referenced list is a negative one, the
8023 effect may not be what you intended, because the negation does not propagate
8024 out to the higher level. For example, consider:
8026 domainlist dom1 = !a.b
8027 domainlist dom2 = +dom1 : *.b
8029 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8030 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8031 means it matches the second list as well. The effect is not the same as
8033 domainlist dom2 = !a.b : *.b
8035 where &'x.y'& does not match. It's best to avoid negation altogether in
8036 referenced lists if you can.
8038 Named lists may have a performance advantage. When Exim is routing an
8039 address or checking an incoming message, it caches the result of tests on named
8040 lists. So, if you have a setting such as
8042 domains = +local_domains
8044 on several of your routers
8045 or in several ACL statements,
8046 the actual test is done only for the first one. However, the caching works only
8047 if there are no expansions within the list itself or any sublists that it
8048 references. In other words, caching happens only for lists that are known to be
8049 the same each time they are referenced.
8051 By default, there may be up to 16 named lists of each type. This limit can be
8052 extended by changing a compile-time variable. The use of domain and host lists
8053 is recommended for concepts such as local domains, relay domains, and relay
8054 hosts. The default configuration is set up like this.
8058 .section "Named lists compared with macros" "SECID78"
8059 .cindex "list" "named compared with macro"
8060 .cindex "macro" "compared with named list"
8061 At first sight, named lists might seem to be no different from macros in the
8062 configuration file. However, macros are just textual substitutions. If you
8065 ALIST = host1 : host2
8066 auth_advertise_hosts = !ALIST
8068 it probably won't do what you want, because that is exactly the same as
8070 auth_advertise_hosts = !host1 : host2
8072 Notice that the second host name is not negated. However, if you use a host
8075 hostlist alist = host1 : host2
8076 auth_advertise_hosts = ! +alist
8078 the negation applies to the whole list, and so that is equivalent to
8080 auth_advertise_hosts = !host1 : !host2
8084 .section "Named list caching" "SECID79"
8085 .cindex "list" "caching of named"
8086 .cindex "caching" "named lists"
8087 While processing a message, Exim caches the result of checking a named list if
8088 it is sure that the list is the same each time. In practice, this means that
8089 the cache operates only if the list contains no $ characters, which guarantees
8090 that it will not change when it is expanded. Sometimes, however, you may have
8091 an expanded list that you know will be the same each time within a given
8092 message. For example:
8094 domainlist special_domains = \
8095 ${lookup{$sender_host_address}cdb{/some/file}}
8097 This provides a list of domains that depends only on the sending host's IP
8098 address. If this domain list is referenced a number of times (for example,
8099 in several ACL lines, or in several routers) the result of the check is not
8100 cached by default, because Exim does not know that it is going to be the
8101 same list each time.
8103 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8104 cache the result anyway. For example:
8106 domainlist_cache special_domains = ${lookup{...
8108 If you do this, you should be absolutely sure that caching is going to do
8109 the right thing in all cases. When in doubt, leave it out.
8113 .section "Domain lists" "SECTdomainlist"
8114 .cindex "domain list" "patterns for"
8115 .cindex "list" "domain list"
8116 Domain lists contain patterns that are to be matched against a mail domain.
8117 The following types of item may appear in domain lists:
8120 .cindex "primary host name"
8121 .cindex "host name" "matched in domain list"
8122 .oindex "&%primary_hostname%&"
8123 .cindex "domain list" "matching primary host name"
8124 .cindex "@ in a domain list"
8125 If a pattern consists of a single @ character, it matches the local host name,
8126 as set by the &%primary_hostname%& option (or defaulted). This makes it
8127 possible to use the same configuration file on several different hosts that
8128 differ only in their names.
8130 .cindex "@[] in a domain list"
8131 .cindex "domain list" "matching local IP interfaces"
8132 .cindex "domain literal"
8133 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8134 in square brackets (as in an email address that contains a domain literal), but
8135 only if that IP address is recognized as local for email routing purposes. The
8136 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8137 control which of a host's several IP addresses are treated as local.
8138 In today's Internet, the use of domain literals is controversial.
8141 .cindex "@mx_primary"
8142 .cindex "@mx_secondary"
8143 .cindex "domain list" "matching MX pointers to local host"
8144 If a pattern consists of the string &`@mx_any`& it matches any domain that
8145 has an MX record pointing to the local host or to any host that is listed in
8146 .oindex "&%hosts_treat_as_local%&"
8147 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8148 are similar, except that the first matches only when a primary MX target is the
8149 local host, and the second only when no primary MX target is the local host,
8150 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8151 preference value &-- there may of course be more than one of them.
8153 The MX lookup that takes place when matching a pattern of this type is
8154 performed with the resolver options for widening names turned off. Thus, for
8155 example, a single-component domain will &'not'& be expanded by adding the
8156 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8157 options of the &(dnslookup)& router for a discussion of domain widening.
8159 Sometimes you may want to ignore certain IP addresses when using one of these
8160 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8161 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8162 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8163 on a router). For example:
8165 domains = @mx_any/ignore=127.0.0.1
8167 This example matches any domain that has an MX record pointing to one of
8168 the local host's IP addresses other than 127.0.0.1.
8170 The list of IP addresses is in fact processed by the same code that processes
8171 host lists, so it may contain CIDR-coded network specifications and it may also
8172 contain negative items.
8174 Because the list of IP addresses is a sublist within a domain list, you have to
8175 be careful about delimiters if there is more than one address. Like any other
8176 list, the default delimiter can be changed. Thus, you might have:
8178 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8179 an.other.domain : ...
8181 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8182 involved, it is easiest to change the delimiter for the main list as well:
8184 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8185 an.other.domain ? ...
8188 .cindex "asterisk" "in domain list"
8189 .cindex "domain list" "asterisk in"
8190 .cindex "domain list" "matching &""ends with""&"
8191 If a pattern starts with an asterisk, the remaining characters of the pattern
8192 are compared with the terminating characters of the domain. The use of &"*"& in
8193 domain lists differs from its use in partial matching lookups. In a domain
8194 list, the character following the asterisk need not be a dot, whereas partial
8195 matching works only in terms of dot-separated components. For example, a domain
8196 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8200 .cindex "regular expressions" "in domain list"
8201 .cindex "domain list" "matching regular expression"
8202 If a pattern starts with a circumflex character, it is treated as a regular
8203 expression, and matched against the domain using a regular expression matching
8204 function. The circumflex is treated as part of the regular expression.
8205 Email domains are case-independent, so this regular expression match is by
8206 default case-independent, but you can make it case-dependent by starting it
8207 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8208 are given in chapter &<<CHAPregexp>>&.
8210 &*Warning*&: Because domain lists are expanded before being processed, you
8211 must escape any backslash and dollar characters in the regular expression, or
8212 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8213 it is not to be expanded (unless you really do want to build a regular
8214 expression by expansion, of course).
8216 .cindex "lookup" "in domain list"
8217 .cindex "domain list" "matching by lookup"
8218 If a pattern starts with the name of a single-key lookup type followed by a
8219 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8220 must be a file name in a suitable format for the lookup type. For example, for
8221 &"cdb;"& it must be an absolute path:
8223 domains = cdb;/etc/mail/local_domains.cdb
8225 The appropriate type of lookup is done on the file using the domain name as the
8226 key. In most cases, the data that is looked up is not used; Exim is interested
8227 only in whether or not the key is present in the file. However, when a lookup
8228 is used for the &%domains%& option on a router
8229 or a &%domains%& condition in an ACL statement, the data is preserved in the
8230 &$domain_data$& variable and can be referred to in other router options or
8231 other statements in the same ACL.
8234 Any of the single-key lookup type names may be preceded by
8235 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8237 domains = partial-dbm;/partial/domains
8239 This causes partial matching logic to be invoked; a description of how this
8240 works is given in section &<<SECTpartiallookup>>&.
8243 .cindex "asterisk" "in lookup type"
8244 Any of the single-key lookup types may be followed by an asterisk. This causes
8245 a default lookup for a key consisting of a single asterisk to be done if the
8246 original lookup fails. This is not a useful feature when using a domain list to
8247 select particular domains (because any domain would match), but it might have
8248 value if the result of the lookup is being used via the &$domain_data$&
8251 If the pattern starts with the name of a query-style lookup type followed by a
8252 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8253 pattern must be an appropriate query for the lookup type, as described in
8254 chapter &<<CHAPfdlookup>>&. For example:
8256 hold_domains = mysql;select domain from holdlist \
8257 where domain = '${quote_mysql:$domain}';
8259 In most cases, the data that is looked up is not used (so for an SQL query, for
8260 example, it doesn't matter what field you select). Exim is interested only in
8261 whether or not the query succeeds. However, when a lookup is used for the
8262 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8263 variable and can be referred to in other options.
8265 .cindex "domain list" "matching literal domain name"
8266 If none of the above cases apply, a caseless textual comparison is made
8267 between the pattern and the domain.
8270 Here is an example that uses several different kinds of pattern:
8272 domainlist funny_domains = \
8275 *.foundation.fict.example : \
8276 \N^[1-2]\d{3}\.fict\.example$\N : \
8277 partial-dbm;/opt/data/penguin/book : \
8278 nis;domains.byname : \
8279 nisplus;[name=$domain,status=local],domains.org_dir
8281 There are obvious processing trade-offs among the various matching modes. Using
8282 an asterisk is faster than a regular expression, and listing a few names
8283 explicitly probably is too. The use of a file or database lookup is expensive,
8284 but may be the only option if hundreds of names are required. Because the
8285 patterns are tested in order, it makes sense to put the most commonly matched
8290 .section "Host lists" "SECThostlist"
8291 .cindex "host list" "patterns in"
8292 .cindex "list" "host list"
8293 Host lists are used to control what remote hosts are allowed to do. For
8294 example, some hosts may be allowed to use the local host as a relay, and some
8295 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8296 two different ways, by name or by IP address. In a host list, some types of
8297 pattern are matched to a host name, and some are matched to an IP address.
8298 You need to be particularly careful with this when single-key lookups are
8299 involved, to ensure that the right value is being used as the key.
8302 .section "Special host list patterns" "SECID80"
8303 .cindex "empty item in hosts list"
8304 .cindex "host list" "empty string in"
8305 If a host list item is the empty string, it matches only when no remote host is
8306 involved. This is the case when a message is being received from a local
8307 process using SMTP on the standard input, that is, when a TCP/IP connection is
8310 .cindex "asterisk" "in host list"
8311 The special pattern &"*"& in a host list matches any host or no host. Neither
8312 the IP address nor the name is actually inspected.
8316 .section "Host list patterns that match by IP address" "SECThoslispatip"
8317 .cindex "host list" "matching IP addresses"
8318 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8319 the incoming address actually appears in the IPv6 host as
8320 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8321 list, it is converted into a traditional IPv4 address first. (Not all operating
8322 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8325 The following types of pattern in a host list check the remote host by
8326 inspecting its IP address:
8329 If the pattern is a plain domain name (not a regular expression, not starting
8330 with *, not a lookup of any kind), Exim calls the operating system function
8331 to find the associated IP address(es). Exim uses the newer
8332 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8333 This typically causes a forward DNS lookup of the name. The result is compared
8334 with the IP address of the subject host.
8336 If there is a temporary problem (such as a DNS timeout) with the host name
8337 lookup, a temporary error occurs. For example, if the list is being used in an
8338 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8339 temporary SMTP error code. If no IP address can be found for the host name,
8340 what happens is described in section &<<SECTbehipnot>>& below.
8343 .cindex "@ in a host list"
8344 If the pattern is &"@"&, the primary host name is substituted and used as a
8345 domain name, as just described.
8348 If the pattern is an IP address, it is matched against the IP address of the
8349 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8350 IPv6 addresses can be given in colon-separated format, but the colons have to
8351 be doubled so as not to be taken as item separators when the default list
8352 separator is used. IPv6 addresses are recognized even when Exim is compiled
8353 without IPv6 support. This means that if they appear in a host list on an
8354 IPv4-only host, Exim will not treat them as host names. They are just addresses
8355 that can never match a client host.
8358 .cindex "@[] in a host list"
8359 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8360 the local host. For example, if the local host is an IPv4 host with one
8361 interface address 10.45.23.56, these two ACL statements have the same effect:
8363 accept hosts = 127.0.0.1 : 10.45.23.56
8367 .cindex "CIDR notation"
8368 If the pattern is an IP address followed by a slash and a mask length (for
8369 example 10.11.42.0/24), it is matched against the IP address of the subject
8370 host under the given mask. This allows, an entire network of hosts to be
8371 included (or excluded) by a single item. The mask uses CIDR notation; it
8372 specifies the number of address bits that must match, starting from the most
8373 significant end of the address.
8375 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8376 of a range of addresses. It is the number of bits in the network portion of the
8377 address. The above example specifies a 24-bit netmask, so it matches all 256
8378 addresses in the 10.11.42.0 network. An item such as
8382 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8383 32 for an IPv4 address is the same as no mask at all; just a single address
8386 Here is another example which shows an IPv4 and an IPv6 network:
8388 recipient_unqualified_hosts = 192.168.0.0/16: \
8389 3ffe::ffff::836f::::/48
8391 The doubling of list separator characters applies only when these items
8392 appear inline in a host list. It is not required when indirecting via a file.
8395 recipient_unqualified_hosts = /opt/exim/unqualnets
8397 could make use of a file containing
8402 to have exactly the same effect as the previous example. When listing IPv6
8403 addresses inline, it is usually more convenient to use the facility for
8404 changing separator characters. This list contains the same two networks:
8406 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8409 The separator is changed to semicolon by the leading &"<;"& at the start of the
8415 .section "Host list patterns for single-key lookups by host address" &&&
8416 "SECThoslispatsikey"
8417 .cindex "host list" "lookup of IP address"
8418 When a host is to be identified by a single-key lookup of its complete IP
8419 address, the pattern takes this form:
8421 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8425 hosts_lookup = net-cdb;/hosts-by-ip.db
8427 The text form of the IP address of the subject host is used as the lookup key.
8428 IPv6 addresses are converted to an unabbreviated form, using lower case
8429 letters, with dots as separators because colon is the key terminator in
8430 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8431 quoting the keys, but this is a facility that was added later.] The data
8432 returned by the lookup is not used.
8434 .cindex "IP address" "masking"
8435 .cindex "host list" "masked IP address"
8436 Single-key lookups can also be performed using masked IP addresses, using
8437 patterns of this form:
8439 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8443 net24-dbm;/networks.db
8445 The IP address of the subject host is masked using <&'number'&> as the mask
8446 length. A textual string is constructed from the masked value, followed by the
8447 mask, and this is used as the lookup key. For example, if the host's IP address
8448 is 192.168.34.6, the key that is looked up for the above example is
8449 &"192.168.34.0/24"&.
8451 When an IPv6 address is converted to a string, dots are normally used instead
8452 of colons, so that keys in &(lsearch)& files need not contain colons (which
8453 terminate &(lsearch)& keys). This was implemented some time before the ability
8454 to quote keys was made available in &(lsearch)& files. However, the more
8455 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8456 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8457 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8458 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8459 addresses are always used.
8461 Ideally, it would be nice to tidy up this anomalous situation by changing to
8462 colons in all cases, given that quoting is now available for &(lsearch)&.
8463 However, this would be an incompatible change that might break some existing
8466 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8467 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8468 the former case the key strings include the mask value, whereas in the latter
8469 case the IP address is used on its own.
8473 .section "Host list patterns that match by host name" "SECThoslispatnam"
8474 .cindex "host" "lookup failures"
8475 .cindex "unknown host name"
8476 .cindex "host list" "matching host name"
8477 There are several types of pattern that require Exim to know the name of the
8478 remote host. These are either wildcard patterns or lookups by name. (If a
8479 complete hostname is given without any wildcarding, it is used to find an IP
8480 address to match against, as described in section &<<SECThoslispatip>>&
8483 If the remote host name is not already known when Exim encounters one of these
8484 patterns, it has to be found from the IP address.
8485 Although many sites on the Internet are conscientious about maintaining reverse
8486 DNS data for their hosts, there are also many that do not do this.
8487 Consequently, a name cannot always be found, and this may lead to unwanted
8488 effects. Take care when configuring host lists with wildcarded name patterns.
8489 Consider what will happen if a name cannot be found.
8491 Because of the problems of determining host names from IP addresses, matching
8492 against host names is not as common as matching against IP addresses.
8494 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8495 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8496 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8497 are done can be changed by setting the &%host_lookup_order%& option. For
8498 security, once Exim has found one or more names, it looks up the IP addresses
8499 for these names and compares them with the IP address that it started with.
8500 Only those names whose IP addresses match are accepted. Any other names are
8501 discarded. If no names are left, Exim behaves as if the host name cannot be
8502 found. In the most common case there is only one name and one IP address.
8504 There are some options that control what happens if a host name cannot be
8505 found. These are described in section &<<SECTbehipnot>>& below.
8507 .cindex "host" "alias for"
8508 .cindex "alias for host"
8509 As a result of aliasing, hosts may have more than one name. When processing any
8510 of the following types of pattern, all the host's names are checked:
8513 .cindex "asterisk" "in host list"
8514 If a pattern starts with &"*"& the remainder of the item must match the end of
8515 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8516 &'.b.c'&. This special simple form is provided because this is a very common
8517 requirement. Other kinds of wildcarding require the use of a regular
8520 .cindex "regular expressions" "in host list"
8521 .cindex "host list" "regular expression in"
8522 If the item starts with &"^"& it is taken to be a regular expression which is
8523 matched against the host name. Host names are case-independent, so this regular
8524 expression match is by default case-independent, but you can make it
8525 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8526 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8531 is a regular expression that matches either of the two hosts &'a.c.d'& or
8532 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8533 that backslash and dollar characters are not misinterpreted as part of the
8534 string expansion. The simplest way to do this is to use &`\N`& to mark that
8535 part of the string as non-expandable. For example:
8537 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8539 &*Warning*&: If you want to match a complete host name, you must include the
8540 &`$`& terminating metacharacter in the regular expression, as in the above
8541 example. Without it, a match at the start of the host name is all that is
8548 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8549 .cindex "host" "lookup failures, permanent"
8550 While processing a host list, Exim may need to look up an IP address from a
8551 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8552 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8553 behaviour when it fails to find the information it is seeking is the same.
8555 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8556 apply to temporary DNS errors, whose handling is described in the next section.
8558 .cindex "&`+include_unknown`&"
8559 .cindex "&`+ignore_unknown`&"
8560 Exim parses a host list from left to right. If it encounters a permanent
8561 lookup failure in any item in the host list before it has found a match,
8562 Exim treats it as a failure and the default behavior is as if the host
8563 does not match the list. This may not always be what you want to happen.
8564 To change Exim's behaviour, the special items &`+include_unknown`& or
8565 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8566 not recognized in an indirected file).
8569 If any item that follows &`+include_unknown`& requires information that
8570 cannot found, Exim behaves as if the host does match the list. For example,
8572 host_reject_connection = +include_unknown:*.enemy.ex
8574 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8575 any hosts whose name it cannot find.
8578 If any item that follows &`+ignore_unknown`& requires information that cannot
8579 be found, Exim ignores that item and proceeds to the rest of the list. For
8582 accept hosts = +ignore_unknown : friend.example : \
8585 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8586 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8587 name can be found for 192.168.4.5, it is rejected.
8590 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8591 list. The effect of each one lasts until the next, or until the end of the
8594 .section "Mixing wildcarded host names and addresses in host lists" &&&
8596 .cindex "host list" "mixing names and addresses in"
8598 This section explains the host/ip processing logic with the same concepts
8599 as the previous section, but specifically addresses what happens when a
8600 wildcarded hostname is one of the items in the hostlist.
8603 If you have name lookups or wildcarded host names and
8604 IP addresses in the same host list, you should normally put the IP
8605 addresses first. For example, in an ACL you could have:
8607 accept hosts = 10.9.8.7 : *.friend.example
8609 The reason you normally would order it this way lies in the
8610 left-to-right way that Exim processes lists. It can test IP addresses
8611 without doing any DNS lookups, but when it reaches an item that requires
8612 a host name, it fails if it cannot find a host name to compare with the
8613 pattern. If the above list is given in the opposite order, the
8614 &%accept%& statement fails for a host whose name cannot be found, even
8615 if its IP address is 10.9.8.7.
8618 If you really do want to do the name check first, and still recognize the IP
8619 address, you can rewrite the ACL like this:
8621 accept hosts = *.friend.example
8622 accept hosts = 10.9.8.7
8624 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8625 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8626 &`+ignore_unknown`&, which was discussed in depth in the first example in
8631 .section "Temporary DNS errors when looking up host information" &&&
8633 .cindex "host" "lookup failures, temporary"
8634 .cindex "&`+include_defer`&"
8635 .cindex "&`+ignore_defer`&"
8636 A temporary DNS lookup failure normally causes a defer action (except when
8637 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8638 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8639 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8640 section. These options should be used with care, probably only in non-critical
8641 host lists such as whitelists.
8645 .section "Host list patterns for single-key lookups by host name" &&&
8646 "SECThoslispatnamsk"
8647 .cindex "unknown host name"
8648 .cindex "host list" "matching host name"
8649 If a pattern is of the form
8651 <&'single-key-search-type'&>;<&'search-data'&>
8655 dbm;/host/accept/list
8657 a single-key lookup is performed, using the host name as its key. If the
8658 lookup succeeds, the host matches the item. The actual data that is looked up
8661 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8662 keys in the file, not IP addresses. If you want to do lookups based on IP
8663 addresses, you must precede the search type with &"net-"& (see section
8664 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8665 two items in the same list, one doing an address lookup and one doing a name
8666 lookup, both using the same file.
8670 .section "Host list patterns for query-style lookups" "SECID81"
8671 If a pattern is of the form
8673 <&'query-style-search-type'&>;<&'query'&>
8675 the query is obeyed, and if it succeeds, the host matches the item. The actual
8676 data that is looked up is not used. The variables &$sender_host_address$& and
8677 &$sender_host_name$& can be used in the query. For example:
8679 hosts_lookup = pgsql;\
8680 select ip from hostlist where ip='$sender_host_address'
8682 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8683 can use the &%sg%& expansion item to change this if you need to. If you want to
8684 use masked IP addresses in database queries, you can use the &%mask%& expansion
8687 If the query contains a reference to &$sender_host_name$&, Exim automatically
8688 looks up the host name if it has not already done so. (See section
8689 &<<SECThoslispatnam>>& for comments on finding host names.)
8691 Historical note: prior to release 4.30, Exim would always attempt to find a
8692 host name before running the query, unless the search type was preceded by
8693 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8694 still recognized for query-style lookups, but its presence or absence has no
8695 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8696 See section &<<SECThoslispatsikey>>&.)
8702 .section "Address lists" "SECTaddresslist"
8703 .cindex "list" "address list"
8704 .cindex "address list" "empty item"
8705 .cindex "address list" "patterns"
8706 Address lists contain patterns that are matched against mail addresses. There
8707 is one special case to be considered: the sender address of a bounce message is
8708 always empty. You can test for this by providing an empty item in an address
8709 list. For example, you can set up a router to process bounce messages by
8710 using this option setting:
8714 The presence of the colon creates an empty item. If you do not provide any
8715 data, the list is empty and matches nothing. The empty sender can also be
8716 detected by a regular expression that matches an empty string,
8717 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8719 Non-empty items in an address list can be straightforward email addresses. For
8722 senders = jbc@askone.example : hs@anacreon.example
8724 A certain amount of wildcarding is permitted. If a pattern contains an @
8725 character, but is not a regular expression and does not begin with a
8726 semicolon-terminated lookup type (described below), the local part of the
8727 subject address is compared with the local part of the pattern, which may start
8728 with an asterisk. If the local parts match, the domain is checked in exactly
8729 the same way as for a pattern in a domain list. For example, the domain can be
8730 wildcarded, refer to a named list, or be a lookup:
8732 deny senders = *@*.spamming.site:\
8733 *@+hostile_domains:\
8734 bozo@partial-lsearch;/list/of/dodgy/sites:\
8735 *@dbm;/bad/domains.db
8737 .cindex "local part" "starting with !"
8738 .cindex "address list" "local part starting with !"
8739 If a local part that begins with an exclamation mark is required, it has to be
8740 specified using a regular expression, because otherwise the exclamation mark is
8741 treated as a sign of negation, as is standard in lists.
8743 If a non-empty pattern that is not a regular expression or a lookup does not
8744 contain an @ character, it is matched against the domain part of the subject
8745 address. The only two formats that are recognized this way are a literal
8746 domain, or a domain pattern that starts with *. In both these cases, the effect
8747 is the same as if &`*@`& preceded the pattern. For example:
8749 deny senders = enemy.domain : *.enemy.domain
8752 The following kinds of more complicated address list pattern can match any
8753 address, including the empty address that is characteristic of bounce message
8757 .cindex "regular expressions" "in address list"
8758 .cindex "address list" "regular expression in"
8759 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8760 done against the complete address, with the pattern as the regular expression.
8761 You must take care that backslash and dollar characters are not misinterpreted
8762 as part of the string expansion. The simplest way to do this is to use &`\N`&
8763 to mark that part of the string as non-expandable. For example:
8765 deny senders = \N^.*this.*@example\.com$\N : \
8766 \N^\d{8}.+@spamhaus.example$\N : ...
8768 The &`\N`& sequences are removed by the expansion, so these items do indeed
8769 start with &"^"& by the time they are being interpreted as address patterns.
8772 .cindex "address list" "lookup for complete address"
8773 Complete addresses can be looked up by using a pattern that starts with a
8774 lookup type terminated by a semicolon, followed by the data for the lookup. For
8777 deny senders = cdb;/etc/blocked.senders : \
8778 mysql;select address from blocked where \
8779 address='${quote_mysql:$sender_address}'
8781 Both query-style and single-key lookup types can be used. For a single-key
8782 lookup type, Exim uses the complete address as the key. However, empty keys are
8783 not supported for single-key lookups, so a match against the empty address
8784 always fails. This restriction does not apply to query-style lookups.
8786 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8787 cannot be used, and is ignored if specified, with an entry being written to the
8789 .cindex "*@ with single-key lookup"
8790 However, you can configure lookup defaults, as described in section
8791 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8792 default. For example, with this lookup:
8794 accept senders = lsearch*@;/some/file
8796 the file could contains lines like this:
8798 user1@domain1.example
8801 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8804 nimrod@jaeger.example
8808 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8809 would mean that every address matches, thus rendering the test useless.
8811 &*Warning 2*&: Do not confuse these two kinds of item:
8813 deny recipients = dbm*@;/some/file
8814 deny recipients = *@dbm;/some/file
8816 The first does a whole address lookup, with defaulting, as just described,
8817 because it starts with a lookup type. The second matches the local part and
8818 domain independently, as described in a bullet point below.
8822 The following kinds of address list pattern can match only non-empty addresses.
8823 If the subject address is empty, a match against any of these pattern types
8828 .cindex "@@ with single-key lookup"
8829 .cindex "address list" "@@ lookup type"
8830 .cindex "address list" "split local part and domain"
8831 If a pattern starts with &"@@"& followed by a single-key lookup item
8832 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8833 split into a local part and a domain. The domain is looked up in the file. If
8834 it is not found, there is no match. If it is found, the data that is looked up
8835 from the file is treated as a colon-separated list of local part patterns, each
8836 of which is matched against the subject local part in turn.
8838 .cindex "asterisk" "in address list"
8839 The lookup may be a partial one, and/or one involving a search for a default
8840 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8841 patterns that are looked up can be regular expressions or begin with &"*"&, or
8842 even be further lookups. They may also be independently negated. For example,
8845 deny senders = @@dbm;/etc/reject-by-domain
8847 the data from which the DBM file is built could contain lines like
8849 baddomain.com: !postmaster : *
8851 to reject all senders except &%postmaster%& from that domain.
8853 .cindex "local part" "starting with !"
8854 If a local part that actually begins with an exclamation mark is required, it
8855 has to be specified using a regular expression. In &(lsearch)& files, an entry
8856 may be split over several lines by indenting the second and subsequent lines,
8857 but the separating colon must still be included at line breaks. White space
8858 surrounding the colons is ignored. For example:
8860 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8863 As in all colon-separated lists in Exim, a colon can be included in an item by
8866 If the last item in the list starts with a right angle-bracket, the remainder
8867 of the item is taken as a new key to look up in order to obtain a continuation
8868 list of local parts. The new key can be any sequence of characters. Thus one
8869 might have entries like
8871 aol.com: spammer1 : spammer 2 : >*
8872 xyz.com: spammer3 : >*
8875 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8876 local parts for all domains, in addition to the specific local parts listed for
8877 each domain. Of course, using this feature costs another lookup each time a
8878 chain is followed, but the effort needed to maintain the data is reduced.
8880 .cindex "loop" "in lookups"
8881 It is possible to construct loops using this facility, and in order to catch
8882 them, the chains may be no more than fifty items long.
8885 The @@<&'lookup'&> style of item can also be used with a query-style
8886 lookup, but in this case, the chaining facility is not available. The lookup
8887 can only return a single list of local parts.
8890 &*Warning*&: There is an important difference between the address list items
8891 in these two examples:
8894 senders = *@+my_list
8896 In the first one, &`my_list`& is a named address list, whereas in the second
8897 example it is a named domain list.
8902 .section "Case of letters in address lists" "SECTcasletadd"
8903 .cindex "case of local parts"
8904 .cindex "address list" "case forcing"
8905 .cindex "case forcing in address lists"
8906 Domains in email addresses are always handled caselessly, but for local parts
8907 case may be significant on some systems (see &%caseful_local_part%& for how
8908 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8909 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8910 blocking lists should be done in a case-independent manner. Since most address
8911 lists in Exim are used for this kind of control, Exim attempts to do this by
8914 The domain portion of an address is always lowercased before matching it to an
8915 address list. The local part is lowercased by default, and any string
8916 comparisons that take place are done caselessly. This means that the data in
8917 the address list itself, in files included as plain file names, and in any file
8918 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8919 keys in files that are looked up by a search type other than &(lsearch)& (which
8920 works caselessly) must be in lower case, because these lookups are not
8923 .cindex "&`+caseful`&"
8924 To allow for the possibility of caseful address list matching, if an item in
8925 an address list is the string &"+caseful"&, the original case of the local
8926 part is restored for any comparisons that follow, and string comparisons are no
8927 longer case-independent. This does not affect the domain, which remains in
8928 lower case. However, although independent matches on the domain alone are still
8929 performed caselessly, regular expressions that match against an entire address
8930 become case-sensitive after &"+caseful"& has been seen.
8934 .section "Local part lists" "SECTlocparlis"
8935 .cindex "list" "local part list"
8936 .cindex "local part" "list"
8937 Case-sensitivity in local part lists is handled in the same way as for address
8938 lists, as just described. The &"+caseful"& item can be used if required. In a
8939 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8940 set false, the subject is lowercased and the matching is initially
8941 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8942 matching in the local part list, but not elsewhere in the router. If
8943 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8944 option is case-sensitive from the start.
8946 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8947 comments are handled in the same way as address lists &-- they are recognized
8948 only if the # is preceded by white space or the start of the line.
8949 Otherwise, local part lists are matched in the same way as domain lists, except
8950 that the special items that refer to the local host (&`@`&, &`@[]`&,
8951 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8952 Refer to section &<<SECTdomainlist>>& for details of the other available item
8954 .ecindex IIDdohoadli
8959 . ////////////////////////////////////////////////////////////////////////////
8960 . ////////////////////////////////////////////////////////////////////////////
8962 .chapter "String expansions" "CHAPexpand"
8963 .scindex IIDstrexp "expansion" "of strings"
8964 Many strings in Exim's run time configuration are expanded before use. Some of
8965 them are expanded every time they are used; others are expanded only once.
8967 When a string is being expanded it is copied verbatim from left to right except
8968 when a dollar or backslash character is encountered. A dollar specifies the
8969 start of a portion of the string that is interpreted and replaced as described
8970 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
8971 escape character, as described in the following section.
8973 Whether a string is expanded depends upon the context. Usually this is solely
8974 dependent upon the option for which a value is sought; in this documentation,
8975 options for which string expansion is performed are marked with † after
8976 the data type. ACL rules always expand strings. A couple of expansion
8977 conditions do not expand some of the brace-delimited branches, for security
8982 .section "Literal text in expanded strings" "SECTlittext"
8983 .cindex "expansion" "including literal text"
8984 An uninterpreted dollar can be included in an expanded string by putting a
8985 backslash in front of it. A backslash can be used to prevent any special
8986 character being treated specially in an expansion, including backslash itself.
8987 If the string appears in quotes in the configuration file, two backslashes are
8988 required because the quotes themselves cause interpretation of backslashes when
8989 the string is read in (see section &<<SECTstrings>>&).
8991 .cindex "expansion" "non-expandable substrings"
8992 A portion of the string can specified as non-expandable by placing it between
8993 two occurrences of &`\N`&. This is particularly useful for protecting regular
8994 expressions, which often contain backslashes and dollar signs. For example:
8996 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
8998 On encountering the first &`\N`&, the expander copies subsequent characters
8999 without interpretation until it reaches the next &`\N`& or the end of the
9004 .section "Character escape sequences in expanded strings" "SECID82"
9005 .cindex "expansion" "escape sequences"
9006 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9007 expanded string is recognized as an escape sequence for the character newline,
9008 carriage return, or tab, respectively. A backslash followed by up to three
9009 octal digits is recognized as an octal encoding for a single character, and a
9010 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9013 These escape sequences are also recognized in quoted strings when they are read
9014 in. Their interpretation in expansions as well is useful for unquoted strings,
9015 and for other cases such as looked-up strings that are then expanded.
9018 .section "Testing string expansions" "SECID83"
9019 .cindex "expansion" "testing"
9020 .cindex "testing" "string expansion"
9022 Many expansions can be tested by calling Exim with the &%-be%& option. This
9023 takes the command arguments, or lines from the standard input if there are no
9024 arguments, runs them through the string expansion code, and writes the results
9025 to the standard output. Variables based on configuration values are set up, but
9026 since no message is being processed, variables such as &$local_part$& have no
9027 value. Nevertheless the &%-be%& option can be useful for checking out file and
9028 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9031 Exim gives up its root privilege when it is called with the &%-be%& option, and
9032 instead runs under the uid and gid it was called with, to prevent users from
9033 using &%-be%& for reading files to which they do not have access.
9036 If you want to test expansions that include variables whose values are taken
9037 from a message, there are two other options that can be used. The &%-bem%&
9038 option is like &%-be%& except that it is followed by a file name. The file is
9039 read as a message before doing the test expansions. For example:
9041 exim -bem /tmp/test.message '$h_subject:'
9043 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9044 Exim message identifier. For example:
9046 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9048 This loads the message from Exim's spool before doing the test expansions, and
9049 is therefore restricted to admin users.
9052 .section "Forced expansion failure" "SECTforexpfai"
9053 .cindex "expansion" "forced failure"
9054 A number of expansions that are described in the following section have
9055 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9056 (which are sometimes called &"curly brackets"&). Which of the two strings is
9057 used depends on some condition that is evaluated as part of the expansion. If,
9058 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9059 the entire string expansion fails in a way that can be detected by the code
9060 that requested the expansion. This is called &"forced expansion failure"&, and
9061 its consequences depend on the circumstances. In some cases it is no different
9062 from any other expansion failure, but in others a different action may be
9063 taken. Such variations are mentioned in the documentation of the option that is
9069 .section "Expansion items" "SECTexpansionitems"
9070 The following items are recognized in expanded strings. White space may be used
9071 between sub-items that are keywords or substrings enclosed in braces inside an
9072 outer set of braces, to improve readability. &*Warning*&: Within braces,
9073 white space is significant.
9076 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9077 .cindex "expansion" "variables"
9078 Substitute the contents of the named variable, for example:
9083 The second form can be used to separate the name from subsequent alphanumeric
9084 characters. This form (using braces) is available only for variables; it does
9085 &'not'& apply to message headers. The names of the variables are given in
9086 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9087 given, the expansion fails.
9089 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9090 .cindex "expansion" "operators"
9091 The string is first itself expanded, and then the operation specified by
9092 <&'op'&> is applied to it. For example:
9096 The string starts with the first character after the colon, which may be
9097 leading white space. A list of operators is given in section &<<SECTexpop>>&
9098 below. The operator notation is used for simple expansion items that have just
9099 one argument, because it reduces the number of braces and therefore makes the
9100 string easier to understand.
9102 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9103 This item inserts &"basic"& header lines. It is described with the &%header%&
9104 expansion item below.
9107 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9108 .cindex "expansion" "calling an acl"
9109 .cindex "&%acl%&" "call from expansion"
9110 The name and zero to nine argument strings are first expanded separately. The expanded
9111 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9112 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9113 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9114 and may use the variables; if another acl expansion is used the values
9115 are restored after it returns. If the ACL sets
9116 a value using a "message =" modifier and returns accept or deny, the value becomes
9117 the result of the expansion.
9118 If no message is set and the ACL returns accept or deny
9119 the expansion result is an empty string.
9120 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9123 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9124 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9125 .cindex "expansion" "extracting certificate fields"
9126 .cindex "&%certextract%&" "certificate fields"
9127 .cindex "certificate" "extracting fields"
9128 The <&'certificate'&> must be a variable of type certificate.
9129 The field name is expanded and used to retrieve the relevant field from
9130 the certificate. Supported fields are:
9134 &`subject `& RFC4514 DN
9135 &`issuer `& RFC4514 DN
9140 &`subj_altname `& tagged list
9144 If the field is found,
9145 <&'string2'&> is expanded, and replaces the whole item;
9146 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9147 variable &$value$& contains the value that has been extracted. Afterwards, it
9148 is restored to any previous value it might have had.
9150 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9151 key is not found. If {<&'string2'&>} is also omitted, the value that was
9154 Some field names take optional modifiers, appended and separated by commas.
9156 The field selectors marked as "RFC4514" above
9157 output a Distinguished Name string which is
9159 parseable by Exim as a comma-separated tagged list
9160 (the exceptions being elements containing commas).
9161 RDN elements of a single type may be selected by
9162 a modifier of the type label; if so the expansion
9163 result is a list (newline-separated by default).
9164 The separator may be changed by another modifier of
9165 a right angle-bracket followed immediately by the new separator.
9166 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9168 The field selectors marked as "time" above
9169 take an optional modifier of "int"
9170 for which the result is the number of seconds since epoch.
9171 Otherwise the result is a human-readable string
9172 in the timezone selected by the main "timezone" option.
9174 The field selectors marked as "list" above return a list,
9175 newline-separated by default,
9176 (embedded separator characters in elements are doubled).
9177 The separator may be changed by a modifier of
9178 a right angle-bracket followed immediately by the new separator.
9180 The field selectors marked as "tagged" above
9181 prefix each list element with a type string and an equals sign.
9182 Elements of only one type may be selected by a modifier
9183 which is one of "dns", "uri" or "mail";
9184 if so the element tags are omitted.
9186 If not otherwise noted field values are presented in human-readable form.
9188 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9189 {*&<&'arg'&>&*}...}*&"
9191 This expansion dynamically loads and then calls a locally-written C function.
9192 This functionality is available only if Exim is compiled with
9196 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9197 object so that it doesn't reload the same object file in the same Exim process
9198 (but of course Exim does start new processes frequently).
9200 There may be from zero to eight arguments to the function. When compiling
9201 a local function that is to be called in this way, &_local_scan.h_& should be
9202 included. The Exim variables and functions that are defined by that API
9203 are also available for dynamically loaded functions. The function itself
9204 must have the following type:
9206 int dlfunction(uschar **yield, int argc, uschar *argv[])
9208 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9209 function should return one of the following values:
9211 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9212 into the expanded string that is being built.
9214 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9215 from &'yield'&, if it is set.
9217 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9218 taken from &'yield'& if it is set.
9220 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9222 When compiling a function that is to be used in this way with gcc,
9223 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9224 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9227 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9228 .cindex "expansion" "extracting value from environment"
9229 .cindex "environment" "values from"
9230 The key is first expanded separately, and leading and trailing white space
9232 This is then searched for as a name in the environment.
9233 If a variable is found then its value is placed in &$value$&
9234 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9236 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9237 appear, for example:
9239 ${env{USER}{$value} fail }
9241 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9242 {<&'string1'&>} must be present for &"fail"& to be recognized.
9244 If {<&'string2'&>} is omitted an empty string is substituted on
9246 If {<&'string1'&>} is omitted the search result is substituted on
9249 The environment is adjusted by the &%keep_environment%& and
9250 &%add_environment%& main section options.
9253 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9254 {*&<&'string3'&>&*}}*&"
9255 .cindex "expansion" "extracting substrings by key"
9256 .cindex "&%extract%&" "substrings by key"
9257 The key and <&'string1'&> are first expanded separately. Leading and trailing
9258 white space is removed from the key (but not from any of the strings). The key
9259 must not be empty and must not consist entirely of digits.
9260 The expanded <&'string1'&> must be of the form:
9262 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9265 where the equals signs and spaces (but not both) are optional. If any of the
9266 values contain white space, they must be enclosed in double quotes, and any
9267 values that are enclosed in double quotes are subject to escape processing as
9268 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9269 for the value that corresponds to the key. The search is case-insensitive. If
9270 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9271 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9272 variable &$value$& contains the value that has been extracted. Afterwards, it
9273 is restored to any previous value it might have had.
9275 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9276 key is not found. If {<&'string2'&>} is also omitted, the value that was
9277 extracted is used. Thus, for example, these two expansions are identical, and
9280 ${extract{gid}{uid=1984 gid=2001}}
9281 ${extract{gid}{uid=1984 gid=2001}{$value}}
9283 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9284 appear, for example:
9286 ${extract{Z}{A=... B=...}{$value} fail }
9288 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9289 {<&'string2'&>} must be present for &"fail"& to be recognized.
9292 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9293 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9294 .cindex "expansion" "extracting substrings by number"
9295 .cindex "&%extract%&" "substrings by number"
9296 The <&'number'&> argument must consist entirely of decimal digits,
9297 apart from leading and trailing white space, which is ignored.
9298 This is what distinguishes this form of &%extract%& from the previous kind. It
9299 behaves in the same way, except that, instead of extracting a named field, it
9300 extracts from <&'string1'&> the field whose number is given as the first
9301 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9302 <&'string3'&> as before.
9304 The fields in the string are separated by any one of the characters in the
9305 separator string. These may include space or tab characters.
9306 The first field is numbered one. If the number is negative, the fields are
9307 counted from the end of the string, with the rightmost one numbered -1. If the
9308 number given is zero, the entire string is returned. If the modulus of the
9309 number is greater than the number of fields in the string, the result is the
9310 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9311 provided. For example:
9313 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9317 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9319 yields &"99"&. Two successive separators mean that the field between them is
9320 empty (for example, the fifth field above).
9323 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9324 .cindex "list" "selecting by condition"
9325 .cindex "expansion" "selecting from list by condition"
9327 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9328 default, but the separator can be changed in the usual way. For each item
9329 in this list, its value is place in &$item$&, and then the condition is
9330 evaluated. If the condition is true, &$item$& is added to the output as an
9331 item in a new list; if the condition is false, the item is discarded. The
9332 separator used for the output list is the same as the one used for the
9333 input, but a separator setting is not included in the output. For example:
9335 ${filter{a:b:c}{!eq{$item}{b}}
9337 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9338 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9341 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9342 .cindex "hash function" "textual"
9343 .cindex "expansion" "textual hash"
9344 This is a textual hashing function, and was the first to be implemented in
9345 early versions of Exim. In current releases, there are other hashing functions
9346 (numeric, MD5, and SHA-1), which are described below.
9348 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9349 <&'n'&>. If you are using fixed values for these numbers, that is, if
9350 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9351 use the simpler operator notation that avoids some of the braces:
9353 ${hash_<n>_<m>:<string>}
9355 The second number is optional (in both notations). If <&'n'&> is greater than
9356 or equal to the length of the string, the expansion item returns the string.
9357 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9358 function to the string. The new string consists of characters taken from the
9359 first <&'m'&> characters of the string
9361 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9363 If <&'m'&> is not present the value 26 is used, so that only lower case
9364 letters appear. For example:
9366 &`$hash{3}{monty}} `& yields &`jmg`&
9367 &`$hash{5}{monty}} `& yields &`monty`&
9368 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9371 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9372 &*$h_*&<&'header&~name'&>&*:*&" &&&
9373 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9374 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9375 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9376 &*$rh_*&<&'header&~name'&>&*:*&"
9377 .cindex "expansion" "header insertion"
9378 .vindex "&$header_$&"
9379 .vindex "&$bheader_$&"
9380 .vindex "&$rheader_$&"
9381 .cindex "header lines" "in expansion strings"
9382 .cindex "header lines" "character sets"
9383 .cindex "header lines" "decoding"
9384 Substitute the contents of the named message header line, for example
9388 The newline that terminates a header line is not included in the expansion, but
9389 internal newlines (caused by splitting the header line over several physical
9390 lines) may be present.
9392 The difference between &%rheader%&, &%bheader%&, and &%header%& is in the way
9393 the data in the header line is interpreted.
9396 .cindex "white space" "in header lines"
9397 &%rheader%& gives the original &"raw"& content of the header line, with no
9398 processing at all, and without the removal of leading and trailing white space.
9401 .cindex "base64 encoding" "in header lines"
9402 &%bheader%& removes leading and trailing white space, and then decodes base64
9403 or quoted-printable MIME &"words"& within the header text, but does no
9404 character set translation. If decoding of what looks superficially like a MIME
9405 &"word"& fails, the raw string is returned. If decoding
9406 .cindex "binary zero" "in header line"
9407 produces a binary zero character, it is replaced by a question mark &-- this is
9408 what Exim does for binary zeros that are actually received in header lines.
9411 &%header%& tries to translate the string as decoded by &%bheader%& to a
9412 standard character set. This is an attempt to produce the same string as would
9413 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9414 returned. Translation is attempted only on operating systems that support the
9415 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9416 a system Makefile or in &_Local/Makefile_&.
9419 In a filter file, the target character set for &%header%& can be specified by a
9420 command of the following form:
9422 headers charset "UTF-8"
9424 This command affects all references to &$h_$& (or &$header_$&) expansions in
9425 subsequently obeyed filter commands. In the absence of this command, the target
9426 character set in a filter is taken from the setting of the &%headers_charset%&
9427 option in the runtime configuration. The value of this option defaults to the
9428 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9431 Header names follow the syntax of RFC 2822, which states that they may contain
9432 any printing characters except space and colon. Consequently, curly brackets
9433 &'do not'& terminate header names, and should not be used to enclose them as
9434 if they were variables. Attempting to do so causes a syntax error.
9436 Only header lines that are common to all copies of a message are visible to
9437 this mechanism. These are the original header lines that are received with the
9438 message, and any that are added by an ACL statement or by a system
9439 filter. Header lines that are added to a particular copy of a message by a
9440 router or transport are not accessible.
9442 For incoming SMTP messages, no header lines are visible in
9443 ACLs that are obeyed before the data phase completes,
9444 because the header structure is not set up until the message is received.
9445 They are visible in DKIM, PRDR and DATA ACLs.
9446 Header lines that are added in a RCPT ACL (for example)
9447 are saved until the message's incoming header lines are available, at which
9448 point they are added.
9449 When any of the above ACLs ar
9450 running, however, header lines added by earlier ACLs are visible.
9452 Upper case and lower case letters are synonymous in header names. If the
9453 following character is white space, the terminating colon may be omitted, but
9454 this is not recommended, because you may then forget it when it is needed. When
9455 white space terminates the header name, this white space is included in the
9456 expanded string. If the message does not contain the given header, the
9457 expansion item is replaced by an empty string. (See the &%def%& condition in
9458 section &<<SECTexpcond>>& for a means of testing for the existence of a
9461 If there is more than one header with the same name, they are all concatenated
9462 to form the substitution string, up to a maximum length of 64K. Unless
9463 &%rheader%& is being used, leading and trailing white space is removed from
9464 each header before concatenation, and a completely empty header is ignored. A
9465 newline character is then inserted between non-empty headers, but there is no
9466 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9467 those headers that contain lists of addresses, a comma is also inserted at the
9468 junctions between headers. This does not happen for the &%rheader%& expansion.
9471 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9472 .cindex "expansion" "hmac hashing"
9474 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9475 shared secret and some text into a message authentication code, as specified in
9476 RFC 2104. This differs from &`${md5:secret_text...}`& or
9477 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9478 cryptographic hash, allowing for authentication that is not possible with MD5
9479 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9480 present. For example:
9482 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9484 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9487 dd97e3ba5d1a61b5006108f8c8252953
9489 As an example of how this might be used, you might put in the main part of
9490 an Exim configuration:
9492 SPAMSCAN_SECRET=cohgheeLei2thahw
9494 In a router or a transport you could then have:
9497 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9498 ${hmac{md5}{SPAMSCAN_SECRET}\
9499 {${primary_hostname},${message_exim_id},$h_message-id:}}
9501 Then given a message, you can check where it was scanned by looking at the
9502 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9503 this header line is authentic by recomputing the authentication code from the
9504 host name, message ID and the &'Message-id:'& header line. This can be done
9505 using Exim's &%-be%& option, or by other means, for example by using the
9506 &'hmac_md5_hex()'& function in Perl.
9509 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9510 .cindex "expansion" "conditional"
9511 .cindex "&%if%&, expansion item"
9512 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9513 item; otherwise <&'string2'&> is used. The available conditions are described
9514 in section &<<SECTexpcond>>& below. For example:
9516 ${if eq {$local_part}{postmaster} {yes}{no} }
9518 The second string need not be present; if it is not and the condition is not
9519 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9520 be present instead of the second string (without any curly brackets). In this
9521 case, the expansion is forced to fail if the condition is not true (see section
9522 &<<SECTforexpfai>>&).
9524 If both strings are omitted, the result is the string &`true`& if the condition
9525 is true, and the empty string if the condition is false. This makes it less
9526 cumbersome to write custom ACL and router conditions. For example, instead of
9528 condition = ${if >{$acl_m4}{3}{true}{false}}
9532 condition = ${if >{$acl_m4}{3}}
9537 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9538 .cindex expansion "imap folder"
9539 .cindex "&%imapfolder%& expansion item"
9540 This item converts a (possibly multilevel, or with non-ASCII characters)
9541 folder specification to a Maildir name for filesystem use.
9542 For information on internationalisation support see &<<SECTi18nMDA>>&.
9546 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9547 .cindex "expansion" "string truncation"
9548 .cindex "&%length%& expansion item"
9549 The &%length%& item is used to extract the initial portion of a string. Both
9550 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9551 you are using a fixed value for the number, that is, if <&'string1'&> does not
9552 change when expanded, you can use the simpler operator notation that avoids
9555 ${length_<n>:<string>}
9557 The result of this item is either the first <&'n'&> characters or the whole
9558 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9559 &%strlen%&, which gives the length of a string.
9562 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9563 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9564 .cindex "expansion" "extracting list elements by number"
9565 .cindex "&%listextract%&" "extract list elements by number"
9566 .cindex "list" "extracting elements by number"
9567 The <&'number'&> argument must consist entirely of decimal digits,
9568 apart from an optional leading minus,
9569 and leading and trailing white space (which is ignored).
9571 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9572 default, but the separator can be changed in the usual way.
9574 The first field of the list is numbered one.
9575 If the number is negative, the fields are
9576 counted from the end of the list, with the rightmost one numbered -1.
9577 The numbered element of the list is extracted and placed in &$value$&,
9578 then <&'string2'&> is expanded as the result.
9580 If the modulus of the
9581 number is zero or greater than the number of fields in the string,
9582 the result is the expansion of <&'string3'&>.
9586 ${listextract{2}{x:42:99}}
9590 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9592 yields &"result: 42"&.
9594 If {<&'string3'&>} is omitted, an empty string is used for string3.
9595 If {<&'string2'&>} is also omitted, the value that was
9597 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9600 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9601 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9602 This is the first of one of two different types of lookup item, which are both
9603 described in the next item.
9605 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9606 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9607 .cindex "expansion" "lookup in"
9608 .cindex "file" "lookups"
9609 .cindex "lookup" "in expanded string"
9610 The two forms of lookup item specify data lookups in files and databases, as
9611 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9612 lookups, and the second is used for query-style lookups. The <&'key'&>,
9613 <&'file'&>, and <&'query'&> strings are expanded before use.
9615 If there is any white space in a lookup item which is part of a filter command,
9616 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9617 other place where white space is significant, the lookup item must be enclosed
9618 in double quotes. The use of data lookups in users' filter files may be locked
9619 out by the system administrator.
9622 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9623 During its expansion, the variable &$value$& contains the data returned by the
9624 lookup. Afterwards it reverts to the value it had previously (at the outer
9625 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9626 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9627 string on failure. If <&'string2'&> is provided, it can itself be a nested
9628 lookup, thus providing a mechanism for looking up a default value when the
9629 original lookup fails.
9631 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9632 data for the outer lookup while the parameters of the second lookup are
9633 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9634 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9635 appear, and in this case, if the lookup fails, the entire expansion is forced
9636 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9637 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9638 successful lookup, and nothing in the case of failure.
9640 For single-key lookups, the string &"partial"& is permitted to precede the
9641 search type in order to do partial matching, and * or *@ may follow a search
9642 type to request default lookups if the key does not match (see sections
9643 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9645 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9646 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9647 and non-wild parts of the key during the expansion of the replacement text.
9648 They return to their previous values at the end of the lookup item.
9650 This example looks up the postmaster alias in the conventional alias file:
9652 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9654 This example uses NIS+ to look up the full name of the user corresponding to
9655 the local part of an address, forcing the expansion to fail if it is not found:
9657 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9662 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9663 .cindex "expansion" "list creation"
9665 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9666 default, but the separator can be changed in the usual way. For each item
9667 in this list, its value is place in &$item$&, and then <&'string2'&> is
9668 expanded and added to the output as an item in a new list. The separator used
9669 for the output list is the same as the one used for the input, but a separator
9670 setting is not included in the output. For example:
9672 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9674 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9675 value of &$item$& is restored to what it was before. See also the &*filter*&
9676 and &*reduce*& expansion items.
9678 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9679 .cindex "expansion" "numeric hash"
9680 .cindex "hash function" "numeric"
9681 The three strings are expanded; the first two must yield numbers. Call them
9682 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9683 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9684 can use the simpler operator notation that avoids some of the braces:
9686 ${nhash_<n>_<m>:<string>}
9688 The second number is optional (in both notations). If there is only one number,
9689 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9690 processed by a div/mod hash function that returns two numbers, separated by a
9691 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9694 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9696 returns the string &"6/33"&.
9700 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9701 .cindex "Perl" "use in expanded string"
9702 .cindex "expansion" "calling Perl from"
9703 This item is available only if Exim has been built to include an embedded Perl
9704 interpreter. The subroutine name and the arguments are first separately
9705 expanded, and then the Perl subroutine is called with those arguments. No
9706 additional arguments need be given; the maximum number permitted, including the
9707 name of the subroutine, is nine.
9709 The return value of the subroutine is inserted into the expanded string, unless
9710 the return value is &%undef%&. In that case, the expansion fails in the same
9711 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9712 Whatever you return is evaluated in a scalar context. For example, if you
9713 return the name of a Perl vector, the return value is the size of the vector,
9716 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9717 with the error message that was passed to &%die%&. More details of the embedded
9718 Perl facility are given in chapter &<<CHAPperl>>&.
9720 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9721 out the use of this expansion item in filter files.
9724 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9725 .cindex "&%prvs%& expansion item"
9726 The first argument is a complete email address and the second is secret
9727 keystring. The third argument, specifying a key number, is optional. If absent,
9728 it defaults to 0. The result of the expansion is a prvs-signed email address,
9729 to be typically used with the &%return_path%& option on an &(smtp)& transport
9730 as part of a bounce address tag validation (BATV) scheme. For more discussion
9731 and an example, see section &<<SECTverifyPRVS>>&.
9733 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9734 {*&<&'string'&>&*}}*&"
9735 .cindex "&%prvscheck%& expansion item"
9736 This expansion item is the complement of the &%prvs%& item. It is used for
9737 checking prvs-signed addresses. If the expansion of the first argument does not
9738 yield a syntactically valid prvs-signed address, the whole item expands to the
9739 empty string. When the first argument does expand to a syntactically valid
9740 prvs-signed address, the second argument is expanded, with the prvs-decoded
9741 version of the address and the key number extracted from the address in the
9742 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9744 These two variables can be used in the expansion of the second argument to
9745 retrieve the secret. The validity of the prvs-signed address is then checked
9746 against the secret. The result is stored in the variable &$prvscheck_result$&,
9747 which is empty for failure or &"1"& for success.
9749 The third argument is optional; if it is missing, it defaults to an empty
9750 string. This argument is now expanded. If the result is an empty string, the
9751 result of the expansion is the decoded version of the address. This is the case
9752 whether or not the signature was valid. Otherwise, the result of the expansion
9753 is the expansion of the third argument.
9755 All three variables can be used in the expansion of the third argument.
9756 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9757 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9759 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9760 .cindex "expansion" "inserting an entire file"
9761 .cindex "file" "inserting into expansion"
9762 .cindex "&%readfile%& expansion item"
9763 The file name and end-of-line string are first expanded separately. The file is
9764 then read, and its contents replace the entire item. All newline characters in
9765 the file are replaced by the end-of-line string if it is present. Otherwise,
9766 newlines are left in the string.
9767 String expansion is not applied to the contents of the file. If you want this,
9768 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9769 the string expansion fails.
9771 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9772 locks out the use of this expansion item in filter files.
9776 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9777 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9778 .cindex "expansion" "inserting from a socket"
9779 .cindex "socket, use of in expansion"
9780 .cindex "&%readsocket%& expansion item"
9781 This item inserts data from a Unix domain or TCP socket into the expanded
9782 string. The minimal way of using it uses just two arguments, as in these
9785 ${readsocket{/socket/name}{request string}}
9786 ${readsocket{inet:some.host:1234}{request string}}
9788 For a Unix domain socket, the first substring must be the path to the socket.
9789 For an Internet socket, the first substring must contain &`inet:`& followed by
9790 a host name or IP address, followed by a colon and a port, which can be a
9791 number or the name of a TCP port in &_/etc/services_&. An IP address may
9792 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9795 ${readsocket{inet:[::1]:1234}{request string}}
9797 Only a single host name may be given, but if looking it up yields more than
9798 one IP address, they are each tried in turn until a connection is made. For
9799 both kinds of socket, Exim makes a connection, writes the request string
9800 unless it is an empty string; and no terminating NUL is ever sent)
9801 and reads from the socket until an end-of-file
9802 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9803 extend what can be done. Firstly, you can vary the timeout. For example:
9805 ${readsocket{/socket/name}{request string}{3s}}
9807 The third argument is a list of options, of which the first element is the timeout
9808 and must be present if the argument is given.
9809 Further elements are options of form &'name=value'&.
9810 One option type is currently recognised, defining whether (the default)
9811 or not a shutdown is done on the connection after sending the request.
9812 Example, to not do so (preferred, eg. by some webservers):
9814 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
9816 A fourth argument allows you to change any newlines that are in the data
9817 that is read, in the same way as for &%readfile%& (see above). This example
9818 turns them into spaces:
9820 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9822 As with all expansions, the substrings are expanded before the processing
9823 happens. Errors in these sub-expansions cause the expansion to fail. In
9824 addition, the following errors can occur:
9827 Failure to create a socket file descriptor;
9829 Failure to connect the socket;
9831 Failure to write the request string;
9833 Timeout on reading from the socket.
9836 By default, any of these errors causes the expansion to fail. However, if
9837 you supply a fifth substring, it is expanded and used when any of the above
9838 errors occurs. For example:
9840 ${readsocket{/socket/name}{request string}{3s}{\n}\
9843 You can test for the existence of a Unix domain socket by wrapping this
9844 expansion in &`${if exists`&, but there is a race condition between that test
9845 and the actual opening of the socket, so it is safer to use the fifth argument
9846 if you want to be absolutely sure of avoiding an expansion error for a
9847 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9849 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9850 locks out the use of this expansion item in filter files.
9853 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9854 .cindex "expansion" "reducing a list to a scalar"
9855 .cindex "list" "reducing to a scalar"
9858 This operation reduces a list to a single, scalar string. After expansion,
9859 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9860 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9861 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9862 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9863 them. The result of that expansion is assigned to &$value$& before the next
9864 iteration. When the end of the list is reached, the final value of &$value$& is
9865 added to the expansion output. The &*reduce*& expansion item can be used in a
9866 number of ways. For example, to add up a list of numbers:
9868 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9870 The result of that expansion would be &`6`&. The maximum of a list of numbers
9873 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9875 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9876 restored to what they were before. See also the &*filter*& and &*map*&
9879 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9880 This item inserts &"raw"& header lines. It is described with the &%header%&
9881 expansion item above.
9883 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9884 {*&<&'string2'&>&*}}*&"
9885 .cindex "expansion" "running a command"
9886 .cindex "&%run%& expansion item"
9887 The command and its arguments are first expanded as one string. The string is
9888 split apart into individual arguments by spaces, and then the command is run
9889 in a separate process, but under the same uid and gid. As in other command
9890 executions from Exim, a shell is not used by default. If the command requires
9891 a shell, you must explicitly code it.
9893 Since the arguments are split by spaces, when there is a variable expansion
9894 which has an empty result, it will cause the situation that the argument will
9895 simply be omitted when the program is actually executed by Exim. If the
9896 script/program requires a specific number of arguments and the expanded
9897 variable could possibly result in this empty expansion, the variable must be
9898 quoted. This is more difficult if the expanded variable itself could result
9899 in a string containing quotes, because it would interfere with the quotes
9900 around the command arguments. A possible guard against this is to wrap the
9901 variable in the &%sg%& operator to change any quote marks to some other
9904 The standard input for the command exists, but is empty. The standard output
9905 and standard error are set to the same file descriptor.
9906 .cindex "return code" "from &%run%& expansion"
9908 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9909 and replaces the entire item; during this expansion, the standard output/error
9910 from the command is in the variable &$value$&. If the command fails,
9911 <&'string2'&>, if present, is expanded and used. Once again, during the
9912 expansion, the standard output/error from the command is in the variable
9915 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
9916 can be the word &"fail"& (not in braces) to force expansion failure if the
9917 command does not succeed. If both strings are omitted, the result is contents
9918 of the standard output/error on success, and nothing on failure.
9920 .vindex "&$run_in_acl$&"
9921 The standard output/error of the command is put in the variable &$value$&.
9922 In this ACL example, the output of a command is logged for the admin to
9925 warn condition = ${run{/usr/bin/id}{yes}{no}}
9926 log_message = Output of id: $value
9928 If the command requires shell idioms, such as the > redirect operator, the
9929 shell must be invoked directly, such as with:
9931 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
9935 The return code from the command is put in the variable &$runrc$&, and this
9936 remains set afterwards, so in a filter file you can do things like this:
9938 if "${run{x y z}{}}$runrc" is 1 then ...
9939 elif $runrc is 2 then ...
9943 If execution of the command fails (for example, the command does not exist),
9944 the return code is 127 &-- the same code that shells use for non-existent
9947 &*Warning*&: In a router or transport, you cannot assume the order in which
9948 option values are expanded, except for those preconditions whose order of
9949 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
9950 by the expansion of one option, and use it in another.
9952 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
9953 out the use of this expansion item in filter files.
9956 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
9957 .cindex "expansion" "string substitution"
9958 .cindex "&%sg%& expansion item"
9959 This item works like Perl's substitution operator (s) with the global (/g)
9960 option; hence its name. However, unlike the Perl equivalent, Exim does not
9961 modify the subject string; instead it returns the modified string for insertion
9962 into the overall expansion. The item takes three arguments: the subject string,
9963 a regular expression, and a substitution string. For example:
9965 ${sg{abcdefabcdef}{abc}{xyz}}
9967 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
9968 if any $ or \ characters are required in the regular expression or in the
9969 substitution string, they have to be escaped. For example:
9971 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
9973 yields &"defabc"&, and
9975 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
9977 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
9978 the regular expression from string expansion.
9982 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
9983 .cindex sorting "a list"
9984 .cindex list sorting
9985 .cindex expansion "list sorting"
9986 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9987 default, but the separator can be changed in the usual way.
9988 The <&'comparator'&> argument is interpreted as the operator
9989 of a two-argument expansion condition.
9990 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
9991 The comparison should return true when applied to two values
9992 if the first value should sort before the second value.
9993 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
9994 the element being placed in &$item$&,
9995 to give values for comparison.
9997 The item result is a sorted list,
9998 with the original list separator,
9999 of the list elements (in full) of the original.
10003 ${sort{3:2:1:4}{<}{$item}}
10005 sorts a list of numbers, and
10007 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10009 will sort an MX lookup into priority order.
10012 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10013 .cindex "&%substr%& expansion item"
10014 .cindex "substring extraction"
10015 .cindex "expansion" "substring extraction"
10016 The three strings are expanded; the first two must yield numbers. Call them
10017 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10018 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10019 can use the simpler operator notation that avoids some of the braces:
10021 ${substr_<n>_<m>:<string>}
10023 The second number is optional (in both notations).
10024 If it is absent in the simpler format, the preceding underscore must also be
10027 The &%substr%& item can be used to extract more general substrings than
10028 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10029 length required. For example
10031 ${substr{3}{2}{$local_part}}
10033 If the starting offset is greater than the string length the result is the
10034 null string; if the length plus starting offset is greater than the string
10035 length, the result is the right-hand part of the string, starting from the
10036 given offset. The first character in the string has offset zero.
10038 The &%substr%& expansion item can take negative offset values to count
10039 from the right-hand end of its operand. The last character is offset -1, the
10040 second-last is offset -2, and so on. Thus, for example,
10042 ${substr{-5}{2}{1234567}}
10044 yields &"34"&. If the absolute value of a negative offset is greater than the
10045 length of the string, the substring starts at the beginning of the string, and
10046 the length is reduced by the amount of overshoot. Thus, for example,
10048 ${substr{-5}{2}{12}}
10050 yields an empty string, but
10052 ${substr{-3}{2}{12}}
10056 When the second number is omitted from &%substr%&, the remainder of the string
10057 is taken if the offset is positive. If it is negative, all characters in the
10058 string preceding the offset point are taken. For example, an offset of -1 and
10059 no length, as in these semantically identical examples:
10062 ${substr{-1}{abcde}}
10064 yields all but the last character of the string, that is, &"abcd"&.
10068 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10069 {*&<&'replacements'&>&*}}*&"
10070 .cindex "expansion" "character translation"
10071 .cindex "&%tr%& expansion item"
10072 This item does single-character translation on its subject string. The second
10073 argument is a list of characters to be translated in the subject string. Each
10074 matching character is replaced by the corresponding character from the
10075 replacement list. For example
10077 ${tr{abcdea}{ac}{13}}
10079 yields &`1b3de1`&. If there are duplicates in the second character string, the
10080 last occurrence is used. If the third string is shorter than the second, its
10081 last character is replicated. However, if it is empty, no translation takes
10087 .section "Expansion operators" "SECTexpop"
10088 .cindex "expansion" "operators"
10089 For expansion items that perform transformations on a single argument string,
10090 the &"operator"& notation is used because it is simpler and uses fewer braces.
10091 The substring is first expanded before the operation is applied to it. The
10092 following operations can be performed:
10095 .vitem &*${address:*&<&'string'&>&*}*&
10096 .cindex "expansion" "RFC 2822 address handling"
10097 .cindex "&%address%& expansion item"
10098 The string is interpreted as an RFC 2822 address, as it might appear in a
10099 header line, and the effective address is extracted from it. If the string does
10100 not parse successfully, the result is empty.
10103 .vitem &*${addresses:*&<&'string'&>&*}*&
10104 .cindex "expansion" "RFC 2822 address handling"
10105 .cindex "&%addresses%& expansion item"
10106 The string (after expansion) is interpreted as a list of addresses in RFC
10107 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10108 operative address (&'local-part@domain'&) is extracted from each item, and the
10109 result of the expansion is a colon-separated list, with appropriate
10110 doubling of colons should any happen to be present in the email addresses.
10111 Syntactically invalid RFC2822 address items are omitted from the output.
10113 It is possible to specify a character other than colon for the output
10114 separator by starting the string with > followed by the new separator
10115 character. For example:
10117 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10119 expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
10120 expansion item, which extracts the working address from a single RFC2822
10121 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10124 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10125 a strict interpretation of header line formatting. Exim parses the bare,
10126 unquoted portion of an email address and if it finds a comma, treats it as an
10127 email address separator. For the example header line:
10129 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10131 The first example below demonstrates that Q-encoded email addresses are parsed
10132 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10133 It does not see the comma because it's still encoded as "=2C". The second
10134 example below is passed the contents of &`$header_from:`&, meaning it gets
10135 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10136 The third example shows that the presence of a comma is skipped when it is
10139 # exim -be '${addresses:From: \
10140 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10142 # exim -be '${addresses:From: Last, First <user@example.com>}'
10143 Last:user@example.com
10144 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10148 .vitem &*${base32:*&<&'digits'&>&*}*&
10149 .cindex "&%base32%& expansion item"
10150 .cindex "expansion" "conversion to base 32"
10151 The string must consist entirely of decimal digits. The number is converted to
10152 base 32 and output as a (empty, for zero) string of characters.
10153 Only lowercase letters are used.
10155 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10156 .cindex "&%base32d%& expansion item"
10157 .cindex "expansion" "conversion to base 32"
10158 The string must consist entirely of base-32 digits.
10159 The number is converted to decimal and output as a string.
10161 .vitem &*${base62:*&<&'digits'&>&*}*&
10162 .cindex "&%base62%& expansion item"
10163 .cindex "expansion" "conversion to base 62"
10164 The string must consist entirely of decimal digits. The number is converted to
10165 base 62 and output as a string of six characters, including leading zeros. In
10166 the few operating environments where Exim uses base 36 instead of base 62 for
10167 its message identifiers (because those systems do not have case-sensitive file
10168 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
10169 be absolutely clear: this is &'not'& base64 encoding.
10171 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10172 .cindex "&%base62d%& expansion item"
10173 .cindex "expansion" "conversion to base 62"
10174 The string must consist entirely of base-62 digits, or, in operating
10175 environments where Exim uses base 36 instead of base 62 for its message
10176 identifiers, base-36 digits. The number is converted to decimal and output as a
10179 .vitem &*${base64:*&<&'string'&>&*}*&
10180 .cindex "expansion" "base64 encoding"
10181 .cindex "base64 encoding" "in string expansion"
10182 .cindex "&%base64%& expansion item"
10183 .cindex certificate "base64 of DER"
10184 This operator converts a string into one that is base64 encoded.
10186 If the string is a single variable of type certificate,
10187 returns the base64 encoding of the DER form of the certificate.
10190 .vitem &*${base64d:*&<&'string'&>&*}*&
10191 .cindex "expansion" "base64 decoding"
10192 .cindex "base64 decoding" "in string expansion"
10193 .cindex "&%base64d%& expansion item"
10194 This operator converts a base64-encoded string into the un-coded form.
10197 .vitem &*${domain:*&<&'string'&>&*}*&
10198 .cindex "domain" "extraction"
10199 .cindex "expansion" "domain extraction"
10200 The string is interpreted as an RFC 2822 address and the domain is extracted
10201 from it. If the string does not parse successfully, the result is empty.
10204 .vitem &*${escape:*&<&'string'&>&*}*&
10205 .cindex "expansion" "escaping non-printing characters"
10206 .cindex "&%escape%& expansion item"
10207 If the string contains any non-printing characters, they are converted to
10208 escape sequences starting with a backslash. Whether characters with the most
10209 significant bit set (so-called &"8-bit characters"&) count as printing or not
10210 is controlled by the &%print_topbitchars%& option.
10212 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10213 .cindex "expansion" "escaping 8-bit characters"
10214 .cindex "&%escape8bit%& expansion item"
10215 If the string contains and characters with the most significant bit set,
10216 they are converted to escape sequences starting with a backslash.
10217 Backslashes and DEL characters are also converted.
10220 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10221 .cindex "expansion" "expression evaluation"
10222 .cindex "expansion" "arithmetic expression"
10223 .cindex "&%eval%& expansion item"
10224 These items supports simple arithmetic and bitwise logical operations in
10225 expansion strings. The string (after expansion) must be a conventional
10226 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10227 logical operators, and parentheses. All operations are carried out using
10228 integer arithmetic. The operator priorities are as follows (the same as in the
10229 C programming language):
10231 .irow &'highest:'& "not (~), negate (-)"
10232 .irow "" "multiply (*), divide (/), remainder (%)"
10233 .irow "" "plus (+), minus (-)"
10234 .irow "" "shift-left (<<), shift-right (>>)"
10235 .irow "" "and (&&)"
10237 .irow &'lowest:'& "or (|)"
10239 Binary operators with the same priority are evaluated from left to right. White
10240 space is permitted before or after operators.
10242 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10243 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10244 decimal, even if they start with a leading zero; hexadecimal numbers are not
10245 permitted. This can be useful when processing numbers extracted from dates or
10246 times, which often do have leading zeros.
10248 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10250 respectively. Negative numbers are supported. The result of the computation is
10251 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10254 &`${eval:1+1} `& yields 2
10255 &`${eval:1+2*3} `& yields 7
10256 &`${eval:(1+2)*3} `& yields 9
10257 &`${eval:2+42%5} `& yields 4
10258 &`${eval:0xc&5} `& yields 4
10259 &`${eval:0xc|5} `& yields 13
10260 &`${eval:0xc^5} `& yields 9
10261 &`${eval:0xc>>1} `& yields 6
10262 &`${eval:0xc<<1} `& yields 24
10263 &`${eval:~255&0x1234} `& yields 4608
10264 &`${eval:-(~255&0x1234)} `& yields -4608
10267 As a more realistic example, in an ACL you might have
10269 deny message = Too many bad recipients
10272 {>{$rcpt_count}{10}} \
10275 {$recipients_count} \
10276 {${eval:$rcpt_count/2}} \
10280 The condition is true if there have been more than 10 RCPT commands and
10281 fewer than half of them have resulted in a valid recipient.
10284 .vitem &*${expand:*&<&'string'&>&*}*&
10285 .cindex "expansion" "re-expansion of substring"
10286 The &%expand%& operator causes a string to be expanded for a second time. For
10289 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10291 first looks up a string in a file while expanding the operand for &%expand%&,
10292 and then re-expands what it has found.
10295 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10297 .cindex "UTF-8" "conversion from"
10298 .cindex "expansion" "UTF-8 conversion"
10299 .cindex "&%from_utf8%& expansion item"
10300 The world is slowly moving towards Unicode, although there are no standards for
10301 email yet. However, other applications (including some databases) are starting
10302 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10303 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10304 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10305 the result is an undefined sequence of bytes.
10307 Unicode code points with values less than 256 are compatible with ASCII and
10308 ISO-8859-1 (also known as Latin-1).
10309 For example, character 169 is the copyright symbol in both cases, though the
10310 way it is encoded is different. In UTF-8, more than one byte is needed for
10311 characters with code values greater than 127, whereas ISO-8859-1 is a
10312 single-byte encoding (but thereby limited to 256 characters). This makes
10313 translation from UTF-8 to ISO-8859-1 straightforward.
10316 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10317 .cindex "hash function" "textual"
10318 .cindex "expansion" "textual hash"
10319 The &%hash%& operator is a simpler interface to the hashing function that can
10320 be used when the two parameters are fixed numbers (as opposed to strings that
10321 change when expanded). The effect is the same as
10323 ${hash{<n>}{<m>}{<string>}}
10325 See the description of the general &%hash%& item above for details. The
10326 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10330 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10331 .cindex "base64 encoding" "conversion from hex"
10332 .cindex "expansion" "hex to base64"
10333 .cindex "&%hex2b64%& expansion item"
10334 This operator converts a hex string into one that is base64 encoded. This can
10335 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10339 .vitem &*${hexquote:*&<&'string'&>&*}*&
10340 .cindex "quoting" "hex-encoded unprintable characters"
10341 .cindex "&%hexquote%& expansion item"
10342 This operator converts non-printable characters in a string into a hex
10343 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10344 as is, and other byte values are converted to &`\xNN`&, for example a
10345 byte value 127 is converted to &`\x7f`&.
10348 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10349 .cindex "&%ipv6denorm%& expansion item"
10350 .cindex "IP address" normalisation
10351 This expands an IPv6 address to a full eight-element colon-separated set
10352 of hex digits including leading zeroes.
10353 A trailing ipv4-style dotted-decimal set is converted to hex.
10354 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10356 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10357 .cindex "&%ipv6norm%& expansion item"
10358 .cindex "IP address" normalisation
10359 .cindex "IP address" "canonical form"
10360 This converts an IPv6 address to canonical form.
10361 Leading zeroes of groups are omitted, and the longest
10362 set of zero-valued groups is replaced with a double colon.
10363 A trailing ipv4-style dotted-decimal set is converted to hex.
10364 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10367 .vitem &*${lc:*&<&'string'&>&*}*&
10368 .cindex "case forcing in strings"
10369 .cindex "string" "case forcing"
10370 .cindex "lower casing"
10371 .cindex "expansion" "case forcing"
10372 .cindex "&%lc%& expansion item"
10373 This forces the letters in the string into lower-case, for example:
10378 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10379 .cindex "expansion" "string truncation"
10380 .cindex "&%length%& expansion item"
10381 The &%length%& operator is a simpler interface to the &%length%& function that
10382 can be used when the parameter is a fixed number (as opposed to a string that
10383 changes when expanded). The effect is the same as
10385 ${length{<number>}{<string>}}
10387 See the description of the general &%length%& item above for details. Note that
10388 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10389 when &%length%& is used as an operator.
10392 .vitem &*${listcount:*&<&'string'&>&*}*&
10393 .cindex "expansion" "list item count"
10394 .cindex "list" "item count"
10395 .cindex "list" "count of items"
10396 .cindex "&%listcount%& expansion item"
10397 The string is interpreted as a list and the number of items is returned.
10400 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10401 .cindex "expansion" "named list"
10402 .cindex "&%listnamed%& expansion item"
10403 The name is interpreted as a named list and the content of the list is returned,
10404 expanding any referenced lists, re-quoting as needed for colon-separation.
10405 If the optional type is given it must be one of "a", "d", "h" or "l"
10406 and selects address-, domain-, host- or localpart- lists to search among respectively.
10407 Otherwise all types are searched in an undefined order and the first
10408 matching list is returned.
10411 .vitem &*${local_part:*&<&'string'&>&*}*&
10412 .cindex "expansion" "local part extraction"
10413 .cindex "&%local_part%& expansion item"
10414 The string is interpreted as an RFC 2822 address and the local part is
10415 extracted from it. If the string does not parse successfully, the result is
10419 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10420 .cindex "masked IP address"
10421 .cindex "IP address" "masking"
10422 .cindex "CIDR notation"
10423 .cindex "expansion" "IP address masking"
10424 .cindex "&%mask%& expansion item"
10425 If the form of the string to be operated on is not an IP address followed by a
10426 slash and an integer (that is, a network address in CIDR notation), the
10427 expansion fails. Otherwise, this operator converts the IP address to binary,
10428 masks off the least significant bits according to the bit count, and converts
10429 the result back to text, with mask appended. For example,
10431 ${mask:10.111.131.206/28}
10433 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10434 be mostly used for looking up masked addresses in files, the result for an IPv6
10435 address uses dots to separate components instead of colons, because colon
10436 terminates a key string in lsearch files. So, for example,
10438 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10442 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10444 Letters in IPv6 addresses are always output in lower case.
10447 .vitem &*${md5:*&<&'string'&>&*}*&
10449 .cindex "expansion" "MD5 hash"
10450 .cindex certificate fingerprint
10451 .cindex "&%md5%& expansion item"
10452 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10453 as a 32-digit hexadecimal number, in which any letters are in lower case.
10455 If the string is a single variable of type certificate,
10456 returns the MD5 hash fingerprint of the certificate.
10459 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10460 .cindex "expansion" "numeric hash"
10461 .cindex "hash function" "numeric"
10462 The &%nhash%& operator is a simpler interface to the numeric hashing function
10463 that can be used when the two parameters are fixed numbers (as opposed to
10464 strings that change when expanded). The effect is the same as
10466 ${nhash{<n>}{<m>}{<string>}}
10468 See the description of the general &%nhash%& item above for details.
10471 .vitem &*${quote:*&<&'string'&>&*}*&
10472 .cindex "quoting" "in string expansions"
10473 .cindex "expansion" "quoting"
10474 .cindex "&%quote%& expansion item"
10475 The &%quote%& operator puts its argument into double quotes if it
10476 is an empty string or
10477 contains anything other than letters, digits, underscores, dots, and hyphens.
10478 Any occurrences of double quotes and backslashes are escaped with a backslash.
10479 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10480 respectively For example,
10488 The place where this is useful is when the argument is a substitution from a
10489 variable or a message header.
10491 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10492 .cindex "&%quote_local_part%& expansion item"
10493 This operator is like &%quote%&, except that it quotes the string only if
10494 required to do so by the rules of RFC 2822 for quoting local parts. For
10495 example, a plus sign would not cause quoting (but it would for &%quote%&).
10496 If you are creating a new email address from the contents of &$local_part$&
10497 (or any other unknown data), you should always use this operator.
10500 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10501 .cindex "quoting" "lookup-specific"
10502 This operator applies lookup-specific quoting rules to the string. Each
10503 query-style lookup type has its own quoting rules which are described with
10504 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10506 ${quote_ldap:two * two}
10512 For single-key lookup types, no quoting is ever necessary and this operator
10513 yields an unchanged string.
10516 .vitem &*${randint:*&<&'n'&>&*}*&
10517 .cindex "random number"
10518 This operator returns a somewhat random number which is less than the
10519 supplied number and is at least 0. The quality of this randomness depends
10520 on how Exim was built; the values are not suitable for keying material.
10521 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10522 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10523 for versions of GnuTLS with that function.
10524 Otherwise, the implementation may be arc4random(), random() seeded by
10525 srandomdev() or srandom(), or a custom implementation even weaker than
10529 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10530 .cindex "expansion" "IP address"
10531 This operator reverses an IP address; for IPv4 addresses, the result is in
10532 dotted-quad decimal form, while for IPv6 addresses the result is in
10533 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10534 for DNS. For example,
10536 ${reverse_ip:192.0.2.4}
10537 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10542 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10546 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10547 .cindex "expansion" "RFC 2047"
10548 .cindex "RFC 2047" "expansion operator"
10549 .cindex "&%rfc2047%& expansion item"
10550 This operator encodes text according to the rules of RFC 2047. This is an
10551 encoding that is used in header lines to encode non-ASCII characters. It is
10552 assumed that the input string is in the encoding specified by the
10553 &%headers_charset%& option, which gets its default at build time. If the string
10554 contains only characters in the range 33&--126, and no instances of the
10557 ? = ( ) < > @ , ; : \ " . [ ] _
10559 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10560 string, using as many &"encoded words"& as necessary to encode all the
10564 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10565 .cindex "expansion" "RFC 2047"
10566 .cindex "RFC 2047" "decoding"
10567 .cindex "&%rfc2047d%& expansion item"
10568 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10569 bytes are replaced by question marks. Characters are converted into the
10570 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10571 not recognized unless &%check_rfc2047_length%& is set false.
10573 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10574 access a header line, RFC 2047 decoding is done automatically. You do not need
10575 to use this operator as well.
10579 .vitem &*${rxquote:*&<&'string'&>&*}*&
10580 .cindex "quoting" "in regular expressions"
10581 .cindex "regular expressions" "quoting"
10582 .cindex "&%rxquote%& expansion item"
10583 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10584 characters in its argument. This is useful when substituting the values of
10585 variables or headers inside regular expressions.
10588 .vitem &*${sha1:*&<&'string'&>&*}*&
10589 .cindex "SHA-1 hash"
10590 .cindex "expansion" "SHA-1 hashing"
10591 .cindex certificate fingerprint
10592 .cindex "&%sha1%& expansion item"
10593 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10594 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10596 If the string is a single variable of type certificate,
10597 returns the SHA-1 hash fingerprint of the certificate.
10600 .vitem &*${sha256:*&<&'string'&>&*}*&
10601 .cindex "SHA-256 hash"
10602 .cindex certificate fingerprint
10603 .cindex "expansion" "SHA-256 hashing"
10604 .cindex "&%sha256%& expansion item"
10605 The &%sha256%& operator computes the SHA-256 hash value of the string
10607 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10609 If the string is a single variable of type certificate,
10610 returns the SHA-256 hash fingerprint of the certificate.
10613 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
10614 &*${sha3_<n>:*&<&'string'&>&*}*&
10615 .cindex "SHA3 hash"
10616 .cindex "expansion" "SHA3 hashing"
10617 .cindex "&%sha3%& expansion item"
10618 The &%sha3%& operator computes the SHA3-256 hash value of the string
10620 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10622 If a number is appended, separated by an underbar, it specifies
10623 the output length. Values of 224, 256, 384 and 512 are accepted;
10624 with 256 being the default.
10626 The &%sha3%& expansion item is only supported if Exim has been
10627 compiled with GnuTLS 3.5.0 or later.
10630 .vitem &*${stat:*&<&'string'&>&*}*&
10631 .cindex "expansion" "statting a file"
10632 .cindex "file" "extracting characteristics"
10633 .cindex "&%stat%& expansion item"
10634 The string, after expansion, must be a file path. A call to the &[stat()]&
10635 function is made for this path. If &[stat()]& fails, an error occurs and the
10636 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10637 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10638 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10639 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10640 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10641 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10642 can extract individual fields using the &%extract%& expansion item.
10644 The use of the &%stat%& expansion in users' filter files can be locked out by
10645 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10646 systems for files larger than 2GB.
10648 .vitem &*${str2b64:*&<&'string'&>&*}*&
10649 .cindex "&%str2b64%& expansion item"
10650 Now deprecated, a synonym for the &%base64%& expansion operator.
10654 .vitem &*${strlen:*&<&'string'&>&*}*&
10655 .cindex "expansion" "string length"
10656 .cindex "string" "length in expansion"
10657 .cindex "&%strlen%& expansion item"
10658 The item is replace by the length of the expanded string, expressed as a
10659 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10662 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10663 .cindex "&%substr%& expansion item"
10664 .cindex "substring extraction"
10665 .cindex "expansion" "substring expansion"
10666 The &%substr%& operator is a simpler interface to the &%substr%& function that
10667 can be used when the two parameters are fixed numbers (as opposed to strings
10668 that change when expanded). The effect is the same as
10670 ${substr{<start>}{<length>}{<string>}}
10672 See the description of the general &%substr%& item above for details. The
10673 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10675 .vitem &*${time_eval:*&<&'string'&>&*}*&
10676 .cindex "&%time_eval%& expansion item"
10677 .cindex "time interval" "decoding"
10678 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10681 .vitem &*${time_interval:*&<&'string'&>&*}*&
10682 .cindex "&%time_interval%& expansion item"
10683 .cindex "time interval" "formatting"
10684 The argument (after sub-expansion) must be a sequence of decimal digits that
10685 represents an interval of time as a number of seconds. It is converted into a
10686 number of larger units and output in Exim's normal time format, for example,
10689 .vitem &*${uc:*&<&'string'&>&*}*&
10690 .cindex "case forcing in strings"
10691 .cindex "string" "case forcing"
10692 .cindex "upper casing"
10693 .cindex "expansion" "case forcing"
10694 .cindex "&%uc%& expansion item"
10695 This forces the letters in the string into upper-case.
10697 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10698 .cindex "correction of invalid utf-8 sequences in strings"
10699 .cindex "utf-8" "utf-8 sequences"
10700 .cindex "incorrect utf-8"
10701 .cindex "expansion" "utf-8 forcing"
10702 .cindex "&%utf8clean%& expansion item"
10703 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10705 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
10706 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
10707 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
10708 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
10709 .cindex expansion UTF-8
10710 .cindex UTF-8 expansion
10712 .cindex internationalisation
10713 .cindex "&%utf8_domain_to_alabel%& expansion item"
10714 .cindex "&%utf8_domain_from_alabel%& expansion item"
10715 .cindex "&%utf8_localpart_to_alabel%& expansion item"
10716 .cindex "&%utf8_localpart_from_alabel%& expansion item"
10717 These convert EAI mail name components between UTF-8 and a-label forms.
10718 For information on internationalisation support see &<<SECTi18nMTA>>&.
10726 .section "Expansion conditions" "SECTexpcond"
10727 .scindex IIDexpcond "expansion" "conditions"
10728 The following conditions are available for testing by the &%${if%& construct
10729 while expanding strings:
10732 .vitem &*!*&<&'condition'&>
10733 .cindex "expansion" "negating a condition"
10734 .cindex "negation" "in expansion condition"
10735 Preceding any condition with an exclamation mark negates the result of the
10738 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10739 .cindex "numeric comparison"
10740 .cindex "expansion" "numeric comparison"
10741 There are a number of symbolic operators for doing numeric comparisons. They
10747 &`>= `& greater or equal
10749 &`<= `& less or equal
10753 ${if >{$message_size}{10M} ...
10755 Note that the general negation operator provides for inequality testing. The
10756 two strings must take the form of optionally signed decimal integers,
10757 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10758 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10759 As a special case, the numerical value of an empty string is taken as
10762 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10763 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10764 10M, not if 10M is larger than &$message_size$&.
10767 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10768 {*&<&'arg2'&>&*}...}*&
10769 .cindex "expansion" "calling an acl"
10770 .cindex "&%acl%&" "expansion condition"
10771 The name and zero to nine argument strings are first expanded separately. The expanded
10772 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10773 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10774 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10775 and may use the variables; if another acl expansion is used the values
10776 are restored after it returns. If the ACL sets
10777 a value using a "message =" modifier the variable $value becomes
10778 the result of the expansion, otherwise it is empty.
10779 If the ACL returns accept the condition is true; if deny, false.
10780 If the ACL returns defer the result is a forced-fail.
10782 .vitem &*bool&~{*&<&'string'&>&*}*&
10783 .cindex "expansion" "boolean parsing"
10784 .cindex "&%bool%& expansion condition"
10785 This condition turns a string holding a true or false representation into
10786 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10787 (case-insensitively); also integer numbers map to true if non-zero,
10789 An empty string is treated as false.
10790 Leading and trailing whitespace is ignored;
10791 thus a string consisting only of whitespace is false.
10792 All other string values will result in expansion failure.
10794 When combined with ACL variables, this expansion condition will let you
10795 make decisions in one place and act on those decisions in another place.
10798 ${if bool{$acl_m_privileged_sender} ...
10802 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10803 .cindex "expansion" "boolean parsing"
10804 .cindex "&%bool_lax%& expansion condition"
10805 Like &%bool%&, this condition turns a string into a boolean state. But
10806 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10807 loose definition that the Router &%condition%& option uses. The empty string
10808 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10809 true. Leading and trailing whitespace is ignored.
10811 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10813 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10814 .cindex "expansion" "encrypted comparison"
10815 .cindex "encrypted strings, comparing"
10816 .cindex "&%crypteq%& expansion condition"
10817 This condition is included in the Exim binary if it is built to support any
10818 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10819 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10820 included in the binary.
10822 The &%crypteq%& condition has two arguments. The first is encrypted and
10823 compared against the second, which is already encrypted. The second string may
10824 be in the LDAP form for storing encrypted strings, which starts with the
10825 encryption type in curly brackets, followed by the data. If the second string
10826 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10827 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10828 Typically this will be a field from a password file. An example of an encrypted
10829 string in LDAP form is:
10831 {md5}CY9rzUYh03PK3k6DJie09g==
10833 If such a string appears directly in an expansion, the curly brackets have to
10834 be quoted, because they are part of the expansion syntax. For example:
10836 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10838 The following encryption types (whose names are matched case-independently) are
10843 .cindex "base64 encoding" "in encrypted password"
10844 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10845 printable characters to compare with the remainder of the second string. If the
10846 length of the comparison string is 24, Exim assumes that it is base64 encoded
10847 (as in the above example). If the length is 32, Exim assumes that it is a
10848 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10852 .cindex "SHA-1 hash"
10853 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10854 printable characters to compare with the remainder of the second string. If the
10855 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10856 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10857 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10860 .cindex "&[crypt()]&"
10861 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10862 only the first eight characters of the password. However, in modern operating
10863 systems this is no longer true, and in many cases the entire password is used,
10864 whatever its length.
10867 .cindex "&[crypt16()]&"
10868 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10869 use up to 16 characters of the password in some operating systems. Again, in
10870 modern operating systems, more characters may be used.
10872 Exim has its own version of &[crypt16()]&, which is just a double call to
10873 &[crypt()]&. For operating systems that have their own version, setting
10874 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10875 operating system version instead of its own. This option is set by default in
10876 the OS-dependent &_Makefile_& for those operating systems that are known to
10877 support &[crypt16()]&.
10879 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10880 it was not using the same algorithm as some operating systems' versions. It
10881 turns out that as well as &[crypt16()]& there is a function called
10882 &[bigcrypt()]& in some operating systems. This may or may not use the same
10883 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10885 However, since there is now a move away from the traditional &[crypt()]&
10886 functions towards using SHA1 and other algorithms, tidying up this area of
10887 Exim is seen as very low priority.
10889 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10890 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10891 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10892 default is &`{crypt}`&. Whatever the default, you can always use either
10893 function by specifying it explicitly in curly brackets.
10895 .vitem &*def:*&<&'variable&~name'&>
10896 .cindex "expansion" "checking for empty variable"
10897 .cindex "&%def%& expansion condition"
10898 The &%def%& condition must be followed by the name of one of the expansion
10899 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10900 variable does not contain the empty string. For example:
10902 ${if def:sender_ident {from $sender_ident}}
10904 Note that the variable name is given without a leading &%$%& character. If the
10905 variable does not exist, the expansion fails.
10907 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
10908 &~&*def:h_*&<&'header&~name'&>&*:*&"
10909 .cindex "expansion" "checking header line existence"
10910 This condition is true if a message is being processed and the named header
10911 exists in the message. For example,
10913 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
10915 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
10916 the header name must be terminated by a colon if white space does not follow.
10918 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10919 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10920 .cindex "string" "comparison"
10921 .cindex "expansion" "string comparison"
10922 .cindex "&%eq%& expansion condition"
10923 .cindex "&%eqi%& expansion condition"
10924 The two substrings are first expanded. The condition is true if the two
10925 resulting strings are identical. For &%eq%& the comparison includes the case of
10926 letters, whereas for &%eqi%& the comparison is case-independent.
10928 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
10929 .cindex "expansion" "file existence test"
10930 .cindex "file" "existence test"
10931 .cindex "&%exists%&, expansion condition"
10932 The substring is first expanded and then interpreted as an absolute path. The
10933 condition is true if the named file (or directory) exists. The existence test
10934 is done by calling the &[stat()]& function. The use of the &%exists%& test in
10935 users' filter files may be locked out by the system administrator.
10937 .vitem &*first_delivery*&
10938 .cindex "delivery" "first"
10939 .cindex "first delivery"
10940 .cindex "expansion" "first delivery test"
10941 .cindex "&%first_delivery%& expansion condition"
10942 This condition, which has no data, is true during a message's first delivery
10943 attempt. It is false during any subsequent delivery attempts.
10946 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
10947 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
10948 .cindex "list" "iterative conditions"
10949 .cindex "expansion" "&*forall*& condition"
10950 .cindex "expansion" "&*forany*& condition"
10952 These conditions iterate over a list. The first argument is expanded to form
10953 the list. By default, the list separator is a colon, but it can be changed by
10954 the normal method. The second argument is interpreted as a condition that is to
10955 be applied to each item in the list in turn. During the interpretation of the
10956 condition, the current list item is placed in a variable called &$item$&.
10958 For &*forany*&, interpretation stops if the condition is true for any item, and
10959 the result of the whole condition is true. If the condition is false for all
10960 items in the list, the overall condition is false.
10962 For &*forall*&, interpretation stops if the condition is false for any item,
10963 and the result of the whole condition is false. If the condition is true for
10964 all items in the list, the overall condition is true.
10966 Note that negation of &*forany*& means that the condition must be false for all
10967 items for the overall condition to succeed, and negation of &*forall*& means
10968 that the condition must be false for at least one item. In this example, the
10969 list separator is changed to a comma:
10971 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
10973 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
10974 being processed, to enable these expansion items to be nested.
10976 To scan a named list, expand it with the &*listnamed*& operator.
10979 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10980 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10981 .cindex "string" "comparison"
10982 .cindex "expansion" "string comparison"
10983 .cindex "&%ge%& expansion condition"
10984 .cindex "&%gei%& expansion condition"
10985 The two substrings are first expanded. The condition is true if the first
10986 string is lexically greater than or equal to the second string. For &%ge%& the
10987 comparison includes the case of letters, whereas for &%gei%& the comparison is
10990 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
10991 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10992 .cindex "string" "comparison"
10993 .cindex "expansion" "string comparison"
10994 .cindex "&%gt%& expansion condition"
10995 .cindex "&%gti%& expansion condition"
10996 The two substrings are first expanded. The condition is true if the first
10997 string is lexically greater than the second string. For &%gt%& the comparison
10998 includes the case of letters, whereas for &%gti%& the comparison is
11001 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11002 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11003 .cindex "string" "comparison"
11004 .cindex "list" "iterative conditions"
11005 Both strings are expanded; the second string is treated as a list of simple
11006 strings; if the first string is a member of the second, then the condition
11009 These are simpler to use versions of the more powerful &*forany*& condition.
11010 Examples, and the &*forany*& equivalents:
11012 ${if inlist{needle}{foo:needle:bar}}
11013 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11014 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11015 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11018 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11019 &*isip4&~{*&<&'string'&>&*}*& &&&
11020 &*isip6&~{*&<&'string'&>&*}*&
11021 .cindex "IP address" "testing string format"
11022 .cindex "string" "testing for IP address"
11023 .cindex "&%isip%& expansion condition"
11024 .cindex "&%isip4%& expansion condition"
11025 .cindex "&%isip6%& expansion condition"
11026 The substring is first expanded, and then tested to see if it has the form of
11027 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11028 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11030 For an IPv4 address, the test is for four dot-separated components, each of
11031 which consists of from one to three digits. For an IPv6 address, up to eight
11032 colon-separated components are permitted, each containing from one to four
11033 hexadecimal digits. There may be fewer than eight components if an empty
11034 component (adjacent colons) is present. Only one empty component is permitted.
11036 &*Note*&: The checks are just on the form of the address; actual numerical
11037 values are not considered. Thus, for example, 999.999.999.999 passes the IPv4
11038 check. The main use of these tests is to distinguish between IP addresses and
11039 host names, or between IPv4 and IPv6 addresses. For example, you could use
11041 ${if isip4{$sender_host_address}...
11043 to test which IP version an incoming SMTP connection is using.
11045 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11046 .cindex "LDAP" "use for authentication"
11047 .cindex "expansion" "LDAP authentication test"
11048 .cindex "&%ldapauth%& expansion condition"
11049 This condition supports user authentication using LDAP. See section
11050 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11051 queries. For this use, the query must contain a user name and password. The
11052 query itself is not used, and can be empty. The condition is true if the
11053 password is not empty, and the user name and password are accepted by the LDAP
11054 server. An empty password is rejected without calling LDAP because LDAP binds
11055 with an empty password are considered anonymous regardless of the username, and
11056 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11057 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11061 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11062 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11063 .cindex "string" "comparison"
11064 .cindex "expansion" "string comparison"
11065 .cindex "&%le%& expansion condition"
11066 .cindex "&%lei%& expansion condition"
11067 The two substrings are first expanded. The condition is true if the first
11068 string is lexically less than or equal to the second string. For &%le%& the
11069 comparison includes the case of letters, whereas for &%lei%& the comparison is
11072 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11073 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11074 .cindex "string" "comparison"
11075 .cindex "expansion" "string comparison"
11076 .cindex "&%lt%& expansion condition"
11077 .cindex "&%lti%& expansion condition"
11078 The two substrings are first expanded. The condition is true if the first
11079 string is lexically less than the second string. For &%lt%& the comparison
11080 includes the case of letters, whereas for &%lti%& the comparison is
11084 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11085 .cindex "expansion" "regular expression comparison"
11086 .cindex "regular expressions" "match in expanded string"
11087 .cindex "&%match%& expansion condition"
11088 The two substrings are first expanded. The second is then treated as a regular
11089 expression and applied to the first. Because of the pre-expansion, if the
11090 regular expression contains dollar, or backslash characters, they must be
11091 escaped. Care must also be taken if the regular expression contains braces
11092 (curly brackets). A closing brace must be escaped so that it is not taken as a
11093 premature termination of <&'string2'&>. The easiest approach is to use the
11094 &`\N`& feature to disable expansion of the regular expression.
11097 ${if match {$local_part}{\N^\d{3}\N} ...
11099 If the whole expansion string is in double quotes, further escaping of
11100 backslashes is also required.
11102 The condition is true if the regular expression match succeeds.
11103 The regular expression is not required to begin with a circumflex
11104 metacharacter, but if there is no circumflex, the expression is not anchored,
11105 and it may match anywhere in the subject, not just at the start. If you want
11106 the pattern to match at the end of the subject, you must include the &`$`&
11107 metacharacter at an appropriate point.
11109 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11110 At the start of an &%if%& expansion the values of the numeric variable
11111 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11112 succeeds causes them to be reset to the substrings of that condition and they
11113 will have these values during the expansion of the success string. At the end
11114 of the &%if%& expansion, the previous values are restored. After testing a
11115 combination of conditions using &%or%&, the subsequent values of the numeric
11116 variables are those of the condition that succeeded.
11118 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11119 .cindex "&%match_address%& expansion condition"
11120 See &*match_local_part*&.
11122 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11123 .cindex "&%match_domain%& expansion condition"
11124 See &*match_local_part*&.
11126 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11127 .cindex "&%match_ip%& expansion condition"
11128 This condition matches an IP address to a list of IP address patterns. It must
11129 be followed by two argument strings. The first (after expansion) must be an IP
11130 address or an empty string. The second (not expanded) is a restricted host
11131 list that can match only an IP address, not a host name. For example:
11133 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11135 The specific types of host list item that are permitted in the list are:
11138 An IP address, optionally with a CIDR mask.
11140 A single asterisk, which matches any IP address.
11142 An empty item, which matches only if the IP address is empty. This could be
11143 useful for testing for a locally submitted message or one from specific hosts
11144 in a single test such as
11145 . ==== As this is a nested list, any displays it contains must be indented
11146 . ==== as otherwise they are too far to the left. This comment applies to
11147 . ==== the use of xmlto plus fop. There's no problem when formatting with
11148 . ==== sdop, with or without the extra indent.
11150 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11152 where the first item in the list is the empty string.
11154 The item @[] matches any of the local host's interface addresses.
11156 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11157 even if &`net-`& is not specified. There is never any attempt to turn the IP
11158 address into a host name. The most common type of linear search for
11159 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11160 masks. For example:
11162 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11164 It is of course possible to use other kinds of lookup, and in such a case, you
11165 do need to specify the &`net-`& prefix if you want to specify a specific
11166 address mask, for example:
11168 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11170 However, unless you are combining a &%match_ip%& condition with others, it is
11171 just as easy to use the fact that a lookup is itself a condition, and write:
11173 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11177 Note that <&'string2'&> is not itself subject to string expansion, unless
11178 Exim was built with the EXPAND_LISTMATCH_RHS option.
11180 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11182 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11183 .cindex "domain list" "in expansion condition"
11184 .cindex "address list" "in expansion condition"
11185 .cindex "local part" "list, in expansion condition"
11186 .cindex "&%match_local_part%& expansion condition"
11187 This condition, together with &%match_address%& and &%match_domain%&, make it
11188 possible to test domain, address, and local part lists within expansions. Each
11189 condition requires two arguments: an item and a list to match. A trivial
11192 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11194 In each case, the second argument may contain any of the allowable items for a
11195 list of the appropriate type. Also, because the second argument (after
11196 expansion) is a standard form of list, it is possible to refer to a named list.
11197 Thus, you can use conditions like this:
11199 ${if match_domain{$domain}{+local_domains}{...
11201 .cindex "&`+caseful`&"
11202 For address lists, the matching starts off caselessly, but the &`+caseful`&
11203 item can be used, as in all address lists, to cause subsequent items to
11204 have their local parts matched casefully. Domains are always matched
11207 Note that <&'string2'&> is not itself subject to string expansion, unless
11208 Exim was built with the EXPAND_LISTMATCH_RHS option.
11210 &*Note*&: Host lists are &'not'& supported in this way. This is because
11211 hosts have two identities: a name and an IP address, and it is not clear
11212 how to specify cleanly how such a test would work. However, IP addresses can be
11213 matched using &%match_ip%&.
11215 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11216 .cindex "PAM authentication"
11217 .cindex "AUTH" "with PAM"
11218 .cindex "Solaris" "PAM support"
11219 .cindex "expansion" "PAM authentication test"
11220 .cindex "&%pam%& expansion condition"
11221 &'Pluggable Authentication Modules'&
11222 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
11223 available in the latest releases of Solaris and in some GNU/Linux
11224 distributions. The Exim support, which is intended for use in conjunction with
11225 the SMTP AUTH command, is available only if Exim is compiled with
11229 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11230 in some releases of GNU/Linux &%-ldl%& is also needed.
11232 The argument string is first expanded, and the result must be a
11233 colon-separated list of strings. Leading and trailing white space is ignored.
11234 The PAM module is initialized with the service name &"exim"& and the user name
11235 taken from the first item in the colon-separated data string (<&'string1'&>).
11236 The remaining items in the data string are passed over in response to requests
11237 from the authentication function. In the simple case there will only be one
11238 request, for a password, so the data consists of just two strings.
11240 There can be problems if any of the strings are permitted to contain colon
11241 characters. In the usual way, these have to be doubled to avoid being taken as
11242 separators. If the data is being inserted from a variable, the &%sg%& expansion
11243 item can be used to double any existing colons. For example, the configuration
11244 of a LOGIN authenticator might contain this setting:
11246 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11248 For a PLAIN authenticator you could use:
11250 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11252 In some operating systems, PAM authentication can be done only from a process
11253 running as root. Since Exim is running as the Exim user when receiving
11254 messages, this means that PAM cannot be used directly in those systems.
11255 A patched version of the &'pam_unix'& module that comes with the
11256 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
11257 The patched module allows one special uid/gid combination, in addition to root,
11258 to authenticate. If you build the patched module to allow the Exim user and
11259 group, PAM can then be used from an Exim authenticator.
11262 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11263 .cindex "&'pwcheck'& daemon"
11265 .cindex "expansion" "&'pwcheck'& authentication test"
11266 .cindex "&%pwcheck%& expansion condition"
11267 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11268 This is one way of making it possible for passwords to be checked by a process
11269 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11270 deprecated. Its replacement is &'saslauthd'& (see below).
11272 The pwcheck support is not included in Exim by default. You need to specify
11273 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11274 building Exim. For example:
11276 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11278 You do not need to install the full Cyrus software suite in order to use
11279 the pwcheck daemon. You can compile and install just the daemon alone
11280 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11281 access to the &_/var/pwcheck_& directory.
11283 The &%pwcheck%& condition takes one argument, which must be the user name and
11284 password, separated by a colon. For example, in a LOGIN authenticator
11285 configuration, you might have this:
11287 server_condition = ${if pwcheck{$auth1:$auth2}}
11289 Again, for a PLAIN authenticator configuration, this would be:
11291 server_condition = ${if pwcheck{$auth2:$auth3}}
11293 .vitem &*queue_running*&
11294 .cindex "queue runner" "detecting when delivering from"
11295 .cindex "expansion" "queue runner test"
11296 .cindex "&%queue_running%& expansion condition"
11297 This condition, which has no data, is true during delivery attempts that are
11298 initiated by queue runner processes, and false otherwise.
11301 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11303 .cindex "expansion" "Radius authentication"
11304 .cindex "&%radius%& expansion condition"
11305 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11306 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11307 the Radius client configuration file in order to build Exim with Radius
11310 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11311 library, using the original API. If you are using release 0.4.0 or later of
11312 this library, you need to set
11314 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11316 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11317 &%libradius%& library that comes with FreeBSD. To do this, set
11319 RADIUS_LIB_TYPE=RADLIB
11321 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11322 You may also have to supply a suitable setting in EXTRALIBS so that the
11323 Radius library can be found when Exim is linked.
11325 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11326 Radius client library, which calls the Radius server. The condition is true if
11327 the authentication is successful. For example:
11329 server_condition = ${if radius{<arguments>}}
11333 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11334 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11335 .cindex "&'saslauthd'& daemon"
11337 .cindex "expansion" "&'saslauthd'& authentication test"
11338 .cindex "&%saslauthd%& expansion condition"
11339 This condition supports user authentication using the Cyrus &'saslauthd'&
11340 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11341 Using this daemon is one way of making it possible for passwords to be checked
11342 by a process that is not running as root.
11344 The saslauthd support is not included in Exim by default. You need to specify
11345 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11346 building Exim. For example:
11348 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11350 You do not need to install the full Cyrus software suite in order to use
11351 the saslauthd daemon. You can compile and install just the daemon alone
11352 from the Cyrus SASL library.
11354 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11355 two are mandatory. For example:
11357 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11359 The service and the realm are optional (which is why the arguments are enclosed
11360 in their own set of braces). For details of the meaning of the service and
11361 realm, and how to run the daemon, consult the Cyrus documentation.
11366 .section "Combining expansion conditions" "SECID84"
11367 .cindex "expansion" "combining conditions"
11368 Several conditions can be tested at once by combining them using the &%and%&
11369 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11370 conditions on their own, and precede their lists of sub-conditions. Each
11371 sub-condition must be enclosed in braces within the overall braces that contain
11372 the list. No repetition of &%if%& is used.
11376 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11377 .cindex "&""or""& expansion condition"
11378 .cindex "expansion" "&""or""& of conditions"
11379 The sub-conditions are evaluated from left to right. The condition is true if
11380 any one of the sub-conditions is true.
11383 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11385 When a true sub-condition is found, the following ones are parsed but not
11386 evaluated. If there are several &"match"& sub-conditions the values of the
11387 numeric variables afterwards are taken from the first one that succeeds.
11389 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11390 .cindex "&""and""& expansion condition"
11391 .cindex "expansion" "&""and""& of conditions"
11392 The sub-conditions are evaluated from left to right. The condition is true if
11393 all of the sub-conditions are true. If there are several &"match"&
11394 sub-conditions, the values of the numeric variables afterwards are taken from
11395 the last one. When a false sub-condition is found, the following ones are
11396 parsed but not evaluated.
11398 .ecindex IIDexpcond
11403 .section "Expansion variables" "SECTexpvar"
11404 .cindex "expansion" "variables, list of"
11405 This section contains an alphabetical list of all the expansion variables. Some
11406 of them are available only when Exim is compiled with specific options such as
11407 support for TLS or the content scanning extension.
11410 .vitem "&$0$&, &$1$&, etc"
11411 .cindex "numerical variables (&$1$& &$2$& etc)"
11412 When a &%match%& expansion condition succeeds, these variables contain the
11413 captured substrings identified by the regular expression during subsequent
11414 processing of the success string of the containing &%if%& expansion item.
11415 In the expansion condition case
11416 they do not retain their values afterwards; in fact, their previous
11417 values are restored at the end of processing an &%if%& item. The numerical
11418 variables may also be set externally by some other matching process which
11419 precedes the expansion of the string. For example, the commands available in
11420 Exim filter files include an &%if%& command with its own regular expression
11421 matching condition.
11423 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11424 Within an acl condition, expansion condition or expansion item
11425 any arguments are copied to these variables,
11426 any unused variables being made empty.
11428 .vitem "&$acl_c...$&"
11429 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11430 can be given any name that starts with &$acl_c$& and is at least six characters
11431 long, but the sixth character must be either a digit or an underscore. For
11432 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11433 variables persist throughout the lifetime of an SMTP connection. They can be
11434 used to pass information between ACLs and between different invocations of the
11435 same ACL. When a message is received, the values of these variables are saved
11436 with the message, and can be accessed by filters, routers, and transports
11437 during subsequent delivery.
11439 .vitem "&$acl_m...$&"
11440 These variables are like the &$acl_c...$& variables, except that their values
11441 are reset after a message has been received. Thus, if several messages are
11442 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11443 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11444 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11445 message is received, the values of these variables are saved with the message,
11446 and can be accessed by filters, routers, and transports during subsequent
11449 .vitem &$acl_narg$&
11450 Within an acl condition, expansion condition or expansion item
11451 this variable has the number of arguments.
11453 .vitem &$acl_verify_message$&
11454 .vindex "&$acl_verify_message$&"
11455 After an address verification has failed, this variable contains the failure
11456 message. It retains its value for use in subsequent modifiers. The message can
11457 be preserved by coding like this:
11459 warn !verify = sender
11460 set acl_m0 = $acl_verify_message
11462 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11463 &%log_message%& modifiers, to include information about the verification
11466 .vitem &$address_data$&
11467 .vindex "&$address_data$&"
11468 This variable is set by means of the &%address_data%& option in routers. The
11469 value then remains with the address while it is processed by subsequent routers
11470 and eventually a transport. If the transport is handling multiple addresses,
11471 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11472 for more details. &*Note*&: The contents of &$address_data$& are visible in
11475 If &$address_data$& is set when the routers are called from an ACL to verify
11476 a recipient address, the final value is still in the variable for subsequent
11477 conditions and modifiers of the ACL statement. If routing the address caused it
11478 to be redirected to just one address, the child address is also routed as part
11479 of the verification, and in this case the final value of &$address_data$& is
11480 from the child's routing.
11482 If &$address_data$& is set when the routers are called from an ACL to verify a
11483 sender address, the final value is also preserved, but this time in
11484 &$sender_address_data$&, to distinguish it from data from a recipient
11487 In both cases (recipient and sender verification), the value does not persist
11488 after the end of the current ACL statement. If you want to preserve
11489 these values for longer, you can save them in ACL variables.
11491 .vitem &$address_file$&
11492 .vindex "&$address_file$&"
11493 When, as a result of aliasing, forwarding, or filtering, a message is directed
11494 to a specific file, this variable holds the name of the file when the transport
11495 is running. At other times, the variable is empty. For example, using the
11496 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11498 /home/r2d2/savemail
11500 then when the &(address_file)& transport is running, &$address_file$&
11501 contains the text string &`/home/r2d2/savemail`&.
11502 .cindex "Sieve filter" "value of &$address_file$&"
11503 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11504 then up to the transport configuration to generate an appropriate absolute path
11505 to the relevant file.
11507 .vitem &$address_pipe$&
11508 .vindex "&$address_pipe$&"
11509 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11510 this variable holds the pipe command when the transport is running.
11512 .vitem "&$auth1$& &-- &$auth3$&"
11513 .vindex "&$auth1$&, &$auth2$&, etc"
11514 These variables are used in SMTP authenticators (see chapters
11515 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11517 .vitem &$authenticated_id$&
11518 .cindex "authentication" "id"
11519 .vindex "&$authenticated_id$&"
11520 When a server successfully authenticates a client it may be configured to
11521 preserve some of the authentication information in the variable
11522 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11523 user/password authenticator configuration might preserve the user name for use
11524 in the routers. Note that this is not the same information that is saved in
11525 &$sender_host_authenticated$&.
11526 When a message is submitted locally (that is, not over a TCP connection)
11527 the value of &$authenticated_id$& is normally the login name of the calling
11528 process. However, a trusted user can override this by means of the &%-oMai%&
11529 command line option.
11531 .vitem &$authenticated_fail_id$&
11532 .cindex "authentication" "fail" "id"
11533 .vindex "&$authenticated_fail_id$&"
11534 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11535 will contain the failed authentication id. If more than one authentication
11536 id is attempted, it will contain only the last one. The variable is
11537 available for processing in the ACL's, generally the quit or notquit ACL.
11538 A message to a local recipient could still be accepted without requiring
11539 authentication, which means this variable could also be visible in all of
11543 .vitem &$authenticated_sender$&
11544 .cindex "sender" "authenticated"
11545 .cindex "authentication" "sender"
11546 .cindex "AUTH" "on MAIL command"
11547 .vindex "&$authenticated_sender$&"
11548 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11549 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11550 described in section &<<SECTauthparamail>>&. Unless the data is the string
11551 &"<>"&, it is set as the authenticated sender of the message, and the value is
11552 available during delivery in the &$authenticated_sender$& variable. If the
11553 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11555 .vindex "&$qualify_domain$&"
11556 When a message is submitted locally (that is, not over a TCP connection), the
11557 value of &$authenticated_sender$& is an address constructed from the login
11558 name of the calling process and &$qualify_domain$&, except that a trusted user
11559 can override this by means of the &%-oMas%& command line option.
11562 .vitem &$authentication_failed$&
11563 .cindex "authentication" "failure"
11564 .vindex "&$authentication_failed$&"
11565 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11566 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11567 possible to distinguish between &"did not try to authenticate"&
11568 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11569 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11570 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11571 negative response to an AUTH command, including (for example) an attempt to use
11572 an undefined mechanism.
11574 .vitem &$av_failed$&
11575 .cindex "content scanning" "AV scanner failure"
11576 This variable is available when Exim is compiled with the content-scanning
11577 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11578 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11579 the ACL malware condition.
11581 .vitem &$body_linecount$&
11582 .cindex "message body" "line count"
11583 .cindex "body of message" "line count"
11584 .vindex "&$body_linecount$&"
11585 When a message is being received or delivered, this variable contains the
11586 number of lines in the message's body. See also &$message_linecount$&.
11588 .vitem &$body_zerocount$&
11589 .cindex "message body" "binary zero count"
11590 .cindex "body of message" "binary zero count"
11591 .cindex "binary zero" "in message body"
11592 .vindex "&$body_zerocount$&"
11593 When a message is being received or delivered, this variable contains the
11594 number of binary zero bytes (ASCII NULs) in the message's body.
11596 .vitem &$bounce_recipient$&
11597 .vindex "&$bounce_recipient$&"
11598 This is set to the recipient address of a bounce message while Exim is creating
11599 it. It is useful if a customized bounce message text file is in use (see
11600 chapter &<<CHAPemsgcust>>&).
11602 .vitem &$bounce_return_size_limit$&
11603 .vindex "&$bounce_return_size_limit$&"
11604 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11605 up to a multiple of 1000. It is useful when a customized error message text
11606 file is in use (see chapter &<<CHAPemsgcust>>&).
11608 .vitem &$caller_gid$&
11609 .cindex "gid (group id)" "caller"
11610 .vindex "&$caller_gid$&"
11611 The real group id under which the process that called Exim was running. This is
11612 not the same as the group id of the originator of a message (see
11613 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11614 incarnation normally contains the Exim gid.
11616 .vitem &$caller_uid$&
11617 .cindex "uid (user id)" "caller"
11618 .vindex "&$caller_uid$&"
11619 The real user id under which the process that called Exim was running. This is
11620 not the same as the user id of the originator of a message (see
11621 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11622 incarnation normally contains the Exim uid.
11624 .vitem &$callout_address$&
11625 .vindex "&$callout_address$&"
11626 After a callout for verification, spamd or malware daemon service, the
11627 address that was connected to.
11629 .vitem &$compile_number$&
11630 .vindex "&$compile_number$&"
11631 The building process for Exim keeps a count of the number
11632 of times it has been compiled. This serves to distinguish different
11633 compilations of the same version of the program.
11635 .vitem &$config_dir$&
11636 .vindex "&$config_dir$&"
11637 The directory name of the main configuration file. That is, the content of
11638 &$config_file$& with the last component stripped. The value does not
11639 contain the trailing slash. If &$config_file$& does not contain a slash,
11640 &$config_dir$& is ".".
11642 .vitem &$config_file$&
11643 .vindex "&$config_file$&"
11644 The name of the main configuration file Exim is using.
11646 .vitem &$dkim_cur_signer$& &&&
11647 &$dkim_verify_status$& &&&
11648 &$dkim_verify_reason$& &&&
11649 &$dkim_domain$& &&&
11650 &$dkim_identity$& &&&
11651 &$dkim_selector$& &&&
11653 &$dkim_canon_body$& &&&
11654 &$dkim_canon_headers$& &&&
11655 &$dkim_copiedheaders$& &&&
11656 &$dkim_bodylength$& &&&
11657 &$dkim_created$& &&&
11658 &$dkim_expires$& &&&
11659 &$dkim_headernames$& &&&
11660 &$dkim_key_testing$& &&&
11661 &$dkim_key_nosubdomains$& &&&
11662 &$dkim_key_srvtype$& &&&
11663 &$dkim_key_granularity$& &&&
11664 &$dkim_key_notes$& &&&
11665 &$dkim_key_length$&
11666 These variables are only available within the DKIM ACL.
11667 For details see chapter &<<CHAPdkim>>&.
11669 .vitem &$dkim_signers$&
11670 .vindex &$dkim_signers$&
11671 When a message has been received this variable contains
11672 a colon-separated list of signer domains and identities for the message.
11673 For details see chapter &<<CHAPdkim>>&.
11675 .vitem &$dnslist_domain$& &&&
11676 &$dnslist_matched$& &&&
11677 &$dnslist_text$& &&&
11679 .vindex "&$dnslist_domain$&"
11680 .vindex "&$dnslist_matched$&"
11681 .vindex "&$dnslist_text$&"
11682 .vindex "&$dnslist_value$&"
11683 .cindex "black list (DNS)"
11684 When a DNS (black) list lookup succeeds, these variables are set to contain
11685 the following data from the lookup: the list's domain name, the key that was
11686 looked up, the contents of any associated TXT record, and the value from the
11687 main A record. See section &<<SECID204>>& for more details.
11690 .vindex "&$domain$&"
11691 When an address is being routed, or delivered on its own, this variable
11692 contains the domain. Uppercase letters in the domain are converted into lower
11693 case for &$domain$&.
11695 Global address rewriting happens when a message is received, so the value of
11696 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11697 is set during user filtering, but not during system filtering, because a
11698 message may have many recipients and the system filter is called just once.
11700 When more than one address is being delivered at once (for example, several
11701 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11702 have the same domain. Transports can be restricted to handling only one domain
11703 at a time if the value of &$domain$& is required at transport time &-- this is
11704 the default for local transports. For further details of the environment in
11705 which local transports are run, see chapter &<<CHAPenvironment>>&.
11707 .oindex "&%delay_warning_condition%&"
11708 At the end of a delivery, if all deferred addresses have the same domain, it is
11709 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11711 The &$domain$& variable is also used in some other circumstances:
11714 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11715 the recipient address. The domain of the &'sender'& address is in
11716 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11717 normally set during the running of the MAIL ACL. However, if the sender address
11718 is verified with a callout during the MAIL ACL, the sender domain is placed in
11719 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11720 the &(smtp)& transport.
11723 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11724 &$domain$& contains the domain portion of the address that is being rewritten;
11725 it can be used in the expansion of the replacement address, for example, to
11726 rewrite domains by file lookup.
11729 With one important exception, whenever a domain list is being scanned,
11730 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11731 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11732 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11733 that, in a RCPT ACL, the sender domain list can be dependent on the
11734 recipient domain (which is what is in &$domain$& at this time).
11737 .cindex "ETRN" "value of &$domain$&"
11738 .oindex "&%smtp_etrn_command%&"
11739 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11740 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11744 .vitem &$domain_data$&
11745 .vindex "&$domain_data$&"
11746 When the &%domains%& option on a router matches a domain by
11747 means of a lookup, the data read by the lookup is available during the running
11748 of the router as &$domain_data$&. In addition, if the driver routes the
11749 address to a transport, the value is available in that transport. If the
11750 transport is handling multiple addresses, the value from the first address is
11753 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11754 domain by means of a lookup. The data read by the lookup is available during
11755 the rest of the ACL statement. In all other situations, this variable expands
11758 .vitem &$exim_gid$&
11759 .vindex "&$exim_gid$&"
11760 This variable contains the numerical value of the Exim group id.
11762 .vitem &$exim_path$&
11763 .vindex "&$exim_path$&"
11764 This variable contains the path to the Exim binary.
11766 .vitem &$exim_uid$&
11767 .vindex "&$exim_uid$&"
11768 This variable contains the numerical value of the Exim user id.
11770 .vitem &$exim_version$&
11771 .vindex "&$exim_version$&"
11772 This variable contains the version string of the Exim build.
11773 The first character is a major version number, currently 4.
11774 Then after a dot, the next group of digits is a minor version number.
11775 There may be other characters following the minor version.
11777 .vitem &$header_$&<&'name'&>
11778 This is not strictly an expansion variable. It is expansion syntax for
11779 inserting the message header line with the given name. Note that the name must
11780 be terminated by colon or white space, because it may contain a wide variety of
11781 characters. Note also that braces must &'not'& be used.
11783 .vitem &$headers_added$&
11784 .vindex "&$headers_added$&"
11785 Within an ACL this variable contains the headers added so far by
11786 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11787 The headers are a newline-separated list.
11791 When the &%check_local_user%& option is set for a router, the user's home
11792 directory is placed in &$home$& when the check succeeds. In particular, this
11793 means it is set during the running of users' filter files. A router may also
11794 explicitly set a home directory for use by a transport; this can be overridden
11795 by a setting on the transport itself.
11797 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11798 of the environment variable HOME, which is subject to the
11799 &%keep_environment%& and &%add_environment%& main config options.
11803 If a router assigns an address to a transport (any transport), and passes a
11804 list of hosts with the address, the value of &$host$& when the transport starts
11805 to run is the name of the first host on the list. Note that this applies both
11806 to local and remote transports.
11808 .cindex "transport" "filter"
11809 .cindex "filter" "transport filter"
11810 For the &(smtp)& transport, if there is more than one host, the value of
11811 &$host$& changes as the transport works its way through the list. In
11812 particular, when the &(smtp)& transport is expanding its options for encryption
11813 using TLS, or for specifying a transport filter (see chapter
11814 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11817 When used in the client part of an authenticator configuration (see chapter
11818 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11819 client is connected.
11822 .vitem &$host_address$&
11823 .vindex "&$host_address$&"
11824 This variable is set to the remote host's IP address whenever &$host$& is set
11825 for a remote connection. It is also set to the IP address that is being checked
11826 when the &%ignore_target_hosts%& option is being processed.
11828 .vitem &$host_data$&
11829 .vindex "&$host_data$&"
11830 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11831 result of the lookup is made available in the &$host_data$& variable. This
11832 allows you, for example, to do things like this:
11834 deny hosts = net-lsearch;/some/file
11835 message = $host_data
11837 .vitem &$host_lookup_deferred$&
11838 .cindex "host name" "lookup, failure of"
11839 .vindex "&$host_lookup_deferred$&"
11840 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11841 message comes from a remote host and there is an attempt to look up the host's
11842 name from its IP address, and the attempt is not successful, one of these
11843 variables is set to &"1"&.
11846 If the lookup receives a definite negative response (for example, a DNS lookup
11847 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11850 If there is any kind of problem during the lookup, such that Exim cannot
11851 tell whether or not the host name is defined (for example, a timeout for a DNS
11852 lookup), &$host_lookup_deferred$& is set to &"1"&.
11855 Looking up a host's name from its IP address consists of more than just a
11856 single reverse lookup. Exim checks that a forward lookup of at least one of the
11857 names it receives from a reverse lookup yields the original IP address. If this
11858 is not the case, Exim does not accept the looked up name(s), and
11859 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11860 IP address (for example, the existence of a PTR record in the DNS) is not
11861 sufficient on its own for the success of a host name lookup. If the reverse
11862 lookup succeeds, but there is a lookup problem such as a timeout when checking
11863 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11864 &"1"&. See also &$sender_host_name$&.
11866 .vitem &$host_lookup_failed$&
11867 .vindex "&$host_lookup_failed$&"
11868 See &$host_lookup_deferred$&.
11870 .vitem &$host_port$&
11871 .vindex "&$host_port$&"
11872 This variable is set to the remote host's TCP port whenever &$host$& is set
11873 for an outbound connection.
11875 .vitem &$initial_cwd$&
11876 .vindex "&$initial_cwd$&
11877 This variable contains the full path name of the initial working
11878 directory of the current Exim process. This may differ from the current
11879 working directory, as Exim changes this to "/" during early startup, and
11880 to &$spool_directory$& later.
11883 .vindex "&$inode$&"
11884 The only time this variable is set is while expanding the &%directory_file%&
11885 option in the &(appendfile)& transport. The variable contains the inode number
11886 of the temporary file which is about to be renamed. It can be used to construct
11887 a unique name for the file.
11889 .vitem &$interface_address$&
11890 .vindex "&$interface_address$&"
11891 This is an obsolete name for &$received_ip_address$&.
11893 .vitem &$interface_port$&
11894 .vindex "&$interface_port$&"
11895 This is an obsolete name for &$received_port$&.
11899 This variable is used during the expansion of &*forall*& and &*forany*&
11900 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
11901 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
11905 .vindex "&$ldap_dn$&"
11906 This variable, which is available only when Exim is compiled with LDAP support,
11907 contains the DN from the last entry in the most recently successful LDAP
11910 .vitem &$load_average$&
11911 .vindex "&$load_average$&"
11912 This variable contains the system load average, multiplied by 1000 so that it
11913 is an integer. For example, if the load average is 0.21, the value of the
11914 variable is 210. The value is recomputed every time the variable is referenced.
11916 .vitem &$local_part$&
11917 .vindex "&$local_part$&"
11918 When an address is being routed, or delivered on its own, this
11919 variable contains the local part. When a number of addresses are being
11920 delivered together (for example, multiple RCPT commands in an SMTP
11921 session), &$local_part$& is not set.
11923 Global address rewriting happens when a message is received, so the value of
11924 &$local_part$& during routing and delivery is the value after rewriting.
11925 &$local_part$& is set during user filtering, but not during system filtering,
11926 because a message may have many recipients and the system filter is called just
11929 .vindex "&$local_part_prefix$&"
11930 .vindex "&$local_part_suffix$&"
11931 If a local part prefix or suffix has been recognized, it is not included in the
11932 value of &$local_part$& during routing and subsequent delivery. The values of
11933 any prefix or suffix are in &$local_part_prefix$& and
11934 &$local_part_suffix$&, respectively.
11936 When a message is being delivered to a file, pipe, or autoreply transport as a
11937 result of aliasing or forwarding, &$local_part$& is set to the local part of
11938 the parent address, not to the file name or command (see &$address_file$& and
11941 When an ACL is running for a RCPT command, &$local_part$& contains the
11942 local part of the recipient address.
11944 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11945 &$local_part$& contains the local part of the address that is being rewritten;
11946 it can be used in the expansion of the replacement address, for example.
11948 In all cases, all quoting is removed from the local part. For example, for both
11951 "abc:xyz"@test.example
11952 abc\:xyz@test.example
11954 the value of &$local_part$& is
11958 If you use &$local_part$& to create another address, you should always wrap it
11959 inside a quoting operator. For example, in a &(redirect)& router you could
11962 data = ${quote_local_part:$local_part}@new.domain.example
11964 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
11965 to process local parts in a case-dependent manner in a router, you can set the
11966 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
11968 .vitem &$local_part_data$&
11969 .vindex "&$local_part_data$&"
11970 When the &%local_parts%& option on a router matches a local part by means of a
11971 lookup, the data read by the lookup is available during the running of the
11972 router as &$local_part_data$&. In addition, if the driver routes the address
11973 to a transport, the value is available in that transport. If the transport is
11974 handling multiple addresses, the value from the first address is used.
11976 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
11977 matches a local part by means of a lookup. The data read by the lookup is
11978 available during the rest of the ACL statement. In all other situations, this
11979 variable expands to nothing.
11981 .vitem &$local_part_prefix$&
11982 .vindex "&$local_part_prefix$&"
11983 When an address is being routed or delivered, and a
11984 specific prefix for the local part was recognized, it is available in this
11985 variable, having been removed from &$local_part$&.
11987 .vitem &$local_part_suffix$&
11988 .vindex "&$local_part_suffix$&"
11989 When an address is being routed or delivered, and a
11990 specific suffix for the local part was recognized, it is available in this
11991 variable, having been removed from &$local_part$&.
11993 .vitem &$local_scan_data$&
11994 .vindex "&$local_scan_data$&"
11995 This variable contains the text returned by the &[local_scan()]& function when
11996 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
11998 .vitem &$local_user_gid$&
11999 .vindex "&$local_user_gid$&"
12000 See &$local_user_uid$&.
12002 .vitem &$local_user_uid$&
12003 .vindex "&$local_user_uid$&"
12004 This variable and &$local_user_gid$& are set to the uid and gid after the
12005 &%check_local_user%& router precondition succeeds. This means that their values
12006 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12007 and &%condition%&), for the &%address_data%& expansion, and for any
12008 router-specific expansions. At all other times, the values in these variables
12009 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12011 .vitem &$localhost_number$&
12012 .vindex "&$localhost_number$&"
12013 This contains the expanded value of the
12014 &%localhost_number%& option. The expansion happens after the main options have
12017 .vitem &$log_inodes$&
12018 .vindex "&$log_inodes$&"
12019 The number of free inodes in the disk partition where Exim's
12020 log files are being written. The value is recalculated whenever the variable is
12021 referenced. If the relevant file system does not have the concept of inodes,
12022 the value of is -1. See also the &%check_log_inodes%& option.
12024 .vitem &$log_space$&
12025 .vindex "&$log_space$&"
12026 The amount of free space (as a number of kilobytes) in the disk
12027 partition where Exim's log files are being written. The value is recalculated
12028 whenever the variable is referenced. If the operating system does not have the
12029 ability to find the amount of free space (only true for experimental systems),
12030 the space value is -1. See also the &%check_log_space%& option.
12033 .vitem &$lookup_dnssec_authenticated$&
12034 .vindex "&$lookup_dnssec_authenticated$&"
12035 This variable is set after a DNS lookup done by
12036 a dnsdb lookup expansion, dnslookup router or smtp transport.
12037 .cindex "DNS" "DNSSEC"
12038 It will be empty if &(DNSSEC)& was not requested,
12039 &"no"& if the result was not labelled as authenticated data
12040 and &"yes"& if it was.
12041 Results that are labelled as authoritative answer that match
12042 the &%dns_trust_aa%& configuration variable count also
12043 as authenticated data.
12045 .vitem &$mailstore_basename$&
12046 .vindex "&$mailstore_basename$&"
12047 This variable is set only when doing deliveries in &"mailstore"& format in the
12048 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12049 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12050 contains the basename of the files that are being written, that is, the name
12051 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12054 .vitem &$malware_name$&
12055 .vindex "&$malware_name$&"
12056 This variable is available when Exim is compiled with the
12057 content-scanning extension. It is set to the name of the virus that was found
12058 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12060 .vitem &$max_received_linelength$&
12061 .vindex "&$max_received_linelength$&"
12062 .cindex "maximum" "line length"
12063 .cindex "line length" "maximum"
12064 This variable contains the number of bytes in the longest line that was
12065 received as part of the message, not counting the line termination
12068 .vitem &$message_age$&
12069 .cindex "message" "age of"
12070 .vindex "&$message_age$&"
12071 This variable is set at the start of a delivery attempt to contain the number
12072 of seconds since the message was received. It does not change during a single
12075 .vitem &$message_body$&
12076 .cindex "body of message" "expansion variable"
12077 .cindex "message body" "in expansion"
12078 .cindex "binary zero" "in message body"
12079 .vindex "&$message_body$&"
12080 .oindex "&%message_body_visible%&"
12081 This variable contains the initial portion of a message's body while it is
12082 being delivered, and is intended mainly for use in filter files. The maximum
12083 number of characters of the body that are put into the variable is set by the
12084 &%message_body_visible%& configuration option; the default is 500.
12086 .oindex "&%message_body_newlines%&"
12087 By default, newlines are converted into spaces in &$message_body$&, to make it
12088 easier to search for phrases that might be split over a line break. However,
12089 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12090 zeros are always converted into spaces.
12092 .vitem &$message_body_end$&
12093 .cindex "body of message" "expansion variable"
12094 .cindex "message body" "in expansion"
12095 .vindex "&$message_body_end$&"
12096 This variable contains the final portion of a message's
12097 body while it is being delivered. The format and maximum size are as for
12100 .vitem &$message_body_size$&
12101 .cindex "body of message" "size"
12102 .cindex "message body" "size"
12103 .vindex "&$message_body_size$&"
12104 When a message is being delivered, this variable contains the size of the body
12105 in bytes. The count starts from the character after the blank line that
12106 separates the body from the header. Newlines are included in the count. See
12107 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12109 .vitem &$message_exim_id$&
12110 .vindex "&$message_exim_id$&"
12111 When a message is being received or delivered, this variable contains the
12112 unique message id that is generated and used by Exim to identify the message.
12113 An id is not created for a message until after its header has been successfully
12114 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12115 line; it is the local id that Exim assigns to the message, for example:
12116 &`1BXTIK-0001yO-VA`&.
12118 .vitem &$message_headers$&
12119 .vindex &$message_headers$&
12120 This variable contains a concatenation of all the header lines when a message
12121 is being processed, except for lines added by routers or transports. The header
12122 lines are separated by newline characters. Their contents are decoded in the
12123 same way as a header line that is inserted by &%bheader%&.
12125 .vitem &$message_headers_raw$&
12126 .vindex &$message_headers_raw$&
12127 This variable is like &$message_headers$& except that no processing of the
12128 contents of header lines is done.
12130 .vitem &$message_id$&
12131 This is an old name for &$message_exim_id$&. It is now deprecated.
12133 .vitem &$message_linecount$&
12134 .vindex "&$message_linecount$&"
12135 This variable contains the total number of lines in the header and body of the
12136 message. Compare &$body_linecount$&, which is the count for the body only.
12137 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12138 number of lines received. Before delivery happens (that is, before filters,
12139 routers, and transports run) the count is increased to include the
12140 &'Received:'& header line that Exim standardly adds, and also any other header
12141 lines that are added by ACLs. The blank line that separates the message header
12142 from the body is not counted.
12144 As with the special case of &$message_size$&, during the expansion of the
12145 appendfile transport's maildir_tag option in maildir format, the value of
12146 &$message_linecount$& is the precise size of the number of newlines in the
12147 file that has been written (minus one for the blank line between the
12148 header and the body).
12150 Here is an example of the use of this variable in a DATA ACL:
12152 deny message = Too many lines in message header
12154 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12156 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12157 message has not yet been received.
12159 .vitem &$message_size$&
12160 .cindex "size" "of message"
12161 .cindex "message" "size"
12162 .vindex "&$message_size$&"
12163 When a message is being processed, this variable contains its size in bytes. In
12164 most cases, the size includes those headers that were received with the
12165 message, but not those (such as &'Envelope-to:'&) that are added to individual
12166 deliveries as they are written. However, there is one special case: during the
12167 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12168 doing a delivery in maildir format, the value of &$message_size$& is the
12169 precise size of the file that has been written. See also
12170 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12172 .cindex "RCPT" "value of &$message_size$&"
12173 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12174 contains the size supplied on the MAIL command, or -1 if no size was given. The
12175 value may not, of course, be truthful.
12177 .vitem &$mime_$&&'xxx'&
12178 A number of variables whose names start with &$mime$& are
12179 available when Exim is compiled with the content-scanning extension. For
12180 details, see section &<<SECTscanmimepart>>&.
12182 .vitem "&$n0$& &-- &$n9$&"
12183 These variables are counters that can be incremented by means
12184 of the &%add%& command in filter files.
12186 .vitem &$original_domain$&
12187 .vindex "&$domain$&"
12188 .vindex "&$original_domain$&"
12189 When a top-level address is being processed for delivery, this contains the
12190 same value as &$domain$&. However, if a &"child"& address (for example,
12191 generated by an alias, forward, or filter file) is being processed, this
12192 variable contains the domain of the original address (lower cased). This
12193 differs from &$parent_domain$& only when there is more than one level of
12194 aliasing or forwarding. When more than one address is being delivered in a
12195 single transport run, &$original_domain$& is not set.
12197 If a new address is created by means of a &%deliver%& command in a system
12198 filter, it is set up with an artificial &"parent"& address. This has the local
12199 part &'system-filter'& and the default qualify domain.
12201 .vitem &$original_local_part$&
12202 .vindex "&$local_part$&"
12203 .vindex "&$original_local_part$&"
12204 When a top-level address is being processed for delivery, this contains the
12205 same value as &$local_part$&, unless a prefix or suffix was removed from the
12206 local part, because &$original_local_part$& always contains the full local
12207 part. When a &"child"& address (for example, generated by an alias, forward, or
12208 filter file) is being processed, this variable contains the full local part of
12209 the original address.
12211 If the router that did the redirection processed the local part
12212 case-insensitively, the value in &$original_local_part$& is in lower case.
12213 This variable differs from &$parent_local_part$& only when there is more than
12214 one level of aliasing or forwarding. When more than one address is being
12215 delivered in a single transport run, &$original_local_part$& is not set.
12217 If a new address is created by means of a &%deliver%& command in a system
12218 filter, it is set up with an artificial &"parent"& address. This has the local
12219 part &'system-filter'& and the default qualify domain.
12221 .vitem &$originator_gid$&
12222 .cindex "gid (group id)" "of originating user"
12223 .cindex "sender" "gid"
12224 .vindex "&$caller_gid$&"
12225 .vindex "&$originator_gid$&"
12226 This variable contains the value of &$caller_gid$& that was set when the
12227 message was received. For messages received via the command line, this is the
12228 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12229 normally the gid of the Exim user.
12231 .vitem &$originator_uid$&
12232 .cindex "uid (user id)" "of originating user"
12233 .cindex "sender" "uid"
12234 .vindex "&$caller_uid$&"
12235 .vindex "&$originator_uid$&"
12236 The value of &$caller_uid$& that was set when the message was received. For
12237 messages received via the command line, this is the uid of the sending user.
12238 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12241 .vitem &$parent_domain$&
12242 .vindex "&$parent_domain$&"
12243 This variable is similar to &$original_domain$& (see
12244 above), except that it refers to the immediately preceding parent address.
12246 .vitem &$parent_local_part$&
12247 .vindex "&$parent_local_part$&"
12248 This variable is similar to &$original_local_part$&
12249 (see above), except that it refers to the immediately preceding parent address.
12252 .cindex "pid (process id)" "of current process"
12254 This variable contains the current process id.
12256 .vitem &$pipe_addresses$&
12257 .cindex "filter" "transport filter"
12258 .cindex "transport" "filter"
12259 .vindex "&$pipe_addresses$&"
12260 This is not an expansion variable, but is mentioned here because the string
12261 &`$pipe_addresses`& is handled specially in the command specification for the
12262 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12263 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12264 It cannot be used in general expansion strings, and provokes an &"unknown
12265 variable"& error if encountered.
12267 .vitem &$primary_hostname$&
12268 .vindex "&$primary_hostname$&"
12269 This variable contains the value set by &%primary_hostname%& in the
12270 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12271 a single-component name, Exim calls &[gethostbyname()]& (or
12272 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12273 qualified host name. See also &$smtp_active_hostname$&.
12276 .vitem &$proxy_external_address$& &&&
12277 &$proxy_external_port$& &&&
12278 &$proxy_local_address$& &&&
12279 &$proxy_local_port$& &&&
12281 These variables are only available when built with Proxy Protocol
12283 For details see chapter &<<SECTproxyInbound>>&.
12285 .vitem &$prdr_requested$&
12286 .cindex "PRDR" "variable for"
12287 This variable is set to &"yes"& if PRDR was requested by the client for the
12288 current message, otherwise &"no"&.
12290 .vitem &$prvscheck_address$&
12291 This variable is used in conjunction with the &%prvscheck%& expansion item,
12292 which is described in sections &<<SECTexpansionitems>>& and
12293 &<<SECTverifyPRVS>>&.
12295 .vitem &$prvscheck_keynum$&
12296 This variable is used in conjunction with the &%prvscheck%& expansion item,
12297 which is described in sections &<<SECTexpansionitems>>& and
12298 &<<SECTverifyPRVS>>&.
12300 .vitem &$prvscheck_result$&
12301 This variable is used in conjunction with the &%prvscheck%& expansion item,
12302 which is described in sections &<<SECTexpansionitems>>& and
12303 &<<SECTverifyPRVS>>&.
12305 .vitem &$qualify_domain$&
12306 .vindex "&$qualify_domain$&"
12307 The value set for the &%qualify_domain%& option in the configuration file.
12309 .vitem &$qualify_recipient$&
12310 .vindex "&$qualify_recipient$&"
12311 The value set for the &%qualify_recipient%& option in the configuration file,
12312 or if not set, the value of &$qualify_domain$&.
12314 .vitem &$queue_name$&
12315 .vindex &$queue_name$&
12316 .cindex "named queues"
12317 .cindex queues named
12318 The name of the spool queue in use; empty for the default queue.
12320 .vitem &$rcpt_count$&
12321 .vindex "&$rcpt_count$&"
12322 When a message is being received by SMTP, this variable contains the number of
12323 RCPT commands received for the current message. If this variable is used in a
12324 RCPT ACL, its value includes the current command.
12326 .vitem &$rcpt_defer_count$&
12327 .vindex "&$rcpt_defer_count$&"
12328 .cindex "4&'xx'& responses" "count of"
12329 When a message is being received by SMTP, this variable contains the number of
12330 RCPT commands in the current message that have previously been rejected with a
12331 temporary (4&'xx'&) response.
12333 .vitem &$rcpt_fail_count$&
12334 .vindex "&$rcpt_fail_count$&"
12335 When a message is being received by SMTP, this variable contains the number of
12336 RCPT commands in the current message that have previously been rejected with a
12337 permanent (5&'xx'&) response.
12339 .vitem &$received_count$&
12340 .vindex "&$received_count$&"
12341 This variable contains the number of &'Received:'& header lines in the message,
12342 including the one added by Exim (so its value is always greater than zero). It
12343 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12346 .vitem &$received_for$&
12347 .vindex "&$received_for$&"
12348 If there is only a single recipient address in an incoming message, this
12349 variable contains that address when the &'Received:'& header line is being
12350 built. The value is copied after recipient rewriting has happened, but before
12351 the &[local_scan()]& function is run.
12353 .vitem &$received_ip_address$&
12354 .vindex "&$received_ip_address$&"
12355 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12356 variable is set to the address of the local IP interface, and &$received_port$&
12357 is set to the local port number. (The remote IP address and port are in
12358 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12359 the port value is -1 unless it has been set using the &%-oMi%& command line
12362 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12363 could be used, for example, to make the file name for a TLS certificate depend
12364 on which interface and/or port is being used for the incoming connection. The
12365 values of &$received_ip_address$& and &$received_port$& are saved with any
12366 messages that are received, thus making these variables available at delivery
12368 For outbound connections see &$sending_ip_address$&.
12370 .vitem &$received_port$&
12371 .vindex "&$received_port$&"
12372 See &$received_ip_address$&.
12374 .vitem &$received_protocol$&
12375 .vindex "&$received_protocol$&"
12376 When a message is being processed, this variable contains the name of the
12377 protocol by which it was received. Most of the names used by Exim are defined
12378 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12379 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12380 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12381 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12382 connection and the client was successfully authenticated.
12384 Exim uses the protocol name &"smtps"& for the case when encryption is
12385 automatically set up on connection without the use of STARTTLS (see
12386 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12387 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12388 where the client initially uses EHLO, sets up an encrypted connection using
12389 STARTTLS, and then uses HELO afterwards.
12391 The &%-oMr%& option provides a way of specifying a custom protocol name for
12392 messages that are injected locally by trusted callers. This is commonly used to
12393 identify messages that are being re-injected after some kind of scanning.
12395 .vitem &$received_time$&
12396 .vindex "&$received_time$&"
12397 This variable contains the date and time when the current message was received,
12398 as a number of seconds since the start of the Unix epoch.
12400 .vitem &$recipient_data$&
12401 .vindex "&$recipient_data$&"
12402 This variable is set after an indexing lookup success in an ACL &%recipients%&
12403 condition. It contains the data from the lookup, and the value remains set
12404 until the next &%recipients%& test. Thus, you can do things like this:
12406 &`require recipients = cdb*@;/some/file`&
12407 &`deny `&&'some further test involving'& &`$recipient_data`&
12409 &*Warning*&: This variable is set only when a lookup is used as an indexing
12410 method in the address list, using the semicolon syntax as in the example above.
12411 The variable is not set for a lookup that is used as part of the string
12412 expansion that all such lists undergo before being interpreted.
12414 .vitem &$recipient_verify_failure$&
12415 .vindex "&$recipient_verify_failure$&"
12416 In an ACL, when a recipient verification fails, this variable contains
12417 information about the failure. It is set to one of the following words:
12420 &"qualify"&: The address was unqualified (no domain), and the message
12421 was neither local nor came from an exempted host.
12424 &"route"&: Routing failed.
12427 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12428 or before the MAIL command (that is, on initial connection, HELO, or
12432 &"recipient"&: The RCPT command in a callout was rejected.
12435 &"postmaster"&: The postmaster check in a callout was rejected.
12438 The main use of this variable is expected to be to distinguish between
12439 rejections of MAIL and rejections of RCPT.
12441 .vitem &$recipients$&
12442 .vindex "&$recipients$&"
12443 This variable contains a list of envelope recipients for a message. A comma and
12444 a space separate the addresses in the replacement text. However, the variable
12445 is not generally available, to prevent exposure of Bcc recipients in
12446 unprivileged users' filter files. You can use &$recipients$& only in these
12450 In a system filter file.
12452 In the ACLs associated with the DATA command and with non-SMTP messages, that
12453 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12454 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12455 &%acl_not_smtp_mime%&.
12457 From within a &[local_scan()]& function.
12461 .vitem &$recipients_count$&
12462 .vindex "&$recipients_count$&"
12463 When a message is being processed, this variable contains the number of
12464 envelope recipients that came with the message. Duplicates are not excluded
12465 from the count. While a message is being received over SMTP, the number
12466 increases for each accepted recipient. It can be referenced in an ACL.
12469 .vitem &$regex_match_string$&
12470 .vindex "&$regex_match_string$&"
12471 This variable is set to contain the matching regular expression after a
12472 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12474 .vitem "&$regex1$&, &$regex2$&, etc"
12475 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12476 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12477 these variables contain the
12478 captured substrings identified by the regular expression.
12481 .vitem &$reply_address$&
12482 .vindex "&$reply_address$&"
12483 When a message is being processed, this variable contains the contents of the
12484 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12485 contents of the &'From:'& header line. Apart from the removal of leading
12486 white space, the value is not processed in any way. In particular, no RFC 2047
12487 decoding or character code translation takes place.
12489 .vitem &$return_path$&
12490 .vindex "&$return_path$&"
12491 When a message is being delivered, this variable contains the return path &--
12492 the sender field that will be sent as part of the envelope. It is not enclosed
12493 in <> characters. At the start of routing an address, &$return_path$& has the
12494 same value as &$sender_address$&, but if, for example, an incoming message to a
12495 mailing list has been expanded by a router which specifies a different address
12496 for bounce messages, &$return_path$& subsequently contains the new bounce
12497 address, whereas &$sender_address$& always contains the original sender address
12498 that was received with the message. In other words, &$sender_address$& contains
12499 the incoming envelope sender, and &$return_path$& contains the outgoing
12502 .vitem &$return_size_limit$&
12503 .vindex "&$return_size_limit$&"
12504 This is an obsolete name for &$bounce_return_size_limit$&.
12506 .vitem &$router_name$&
12507 .cindex "router" "name"
12508 .cindex "name" "of router"
12509 .vindex "&$router_name$&"
12510 During the running of a router this variable contains its name.
12513 .cindex "return code" "from &%run%& expansion"
12514 .vindex "&$runrc$&"
12515 This variable contains the return code from a command that is run by the
12516 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12517 assume the order in which option values are expanded, except for those
12518 preconditions whose order of testing is documented. Therefore, you cannot
12519 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12522 .vitem &$self_hostname$&
12523 .oindex "&%self%&" "value of host name"
12524 .vindex "&$self_hostname$&"
12525 When an address is routed to a supposedly remote host that turns out to be the
12526 local host, what happens is controlled by the &%self%& generic router option.
12527 One of its values causes the address to be passed to another router. When this
12528 happens, &$self_hostname$& is set to the name of the local host that the
12529 original router encountered. In other circumstances its contents are null.
12531 .vitem &$sender_address$&
12532 .vindex "&$sender_address$&"
12533 When a message is being processed, this variable contains the sender's address
12534 that was received in the message's envelope. The case of letters in the address
12535 is retained, in both the local part and the domain. For bounce messages, the
12536 value of this variable is the empty string. See also &$return_path$&.
12538 .vitem &$sender_address_data$&
12539 .vindex "&$address_data$&"
12540 .vindex "&$sender_address_data$&"
12541 If &$address_data$& is set when the routers are called from an ACL to verify a
12542 sender address, the final value is preserved in &$sender_address_data$&, to
12543 distinguish it from data from a recipient address. The value does not persist
12544 after the end of the current ACL statement. If you want to preserve it for
12545 longer, you can save it in an ACL variable.
12547 .vitem &$sender_address_domain$&
12548 .vindex "&$sender_address_domain$&"
12549 The domain portion of &$sender_address$&.
12551 .vitem &$sender_address_local_part$&
12552 .vindex "&$sender_address_local_part$&"
12553 The local part portion of &$sender_address$&.
12555 .vitem &$sender_data$&
12556 .vindex "&$sender_data$&"
12557 This variable is set after a lookup success in an ACL &%senders%& condition or
12558 in a router &%senders%& option. It contains the data from the lookup, and the
12559 value remains set until the next &%senders%& test. Thus, you can do things like
12562 &`require senders = cdb*@;/some/file`&
12563 &`deny `&&'some further test involving'& &`$sender_data`&
12565 &*Warning*&: This variable is set only when a lookup is used as an indexing
12566 method in the address list, using the semicolon syntax as in the example above.
12567 The variable is not set for a lookup that is used as part of the string
12568 expansion that all such lists undergo before being interpreted.
12570 .vitem &$sender_fullhost$&
12571 .vindex "&$sender_fullhost$&"
12572 When a message is received from a remote host, this variable contains the host
12573 name and IP address in a single string. It ends with the IP address in square
12574 brackets, followed by a colon and a port number if the logging of ports is
12575 enabled. The format of the rest of the string depends on whether the host
12576 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12577 looking up its IP address. (Looking up the IP address can be forced by the
12578 &%host_lookup%& option, independent of verification.) A plain host name at the
12579 start of the string is a verified host name; if this is not present,
12580 verification either failed or was not requested. A host name in parentheses is
12581 the argument of a HELO or EHLO command. This is omitted if it is identical to
12582 the verified host name or to the host's IP address in square brackets.
12584 .vitem &$sender_helo_dnssec$&
12585 .vindex "&$sender_helo_dnssec$&"
12586 This boolean variable is true if a successful HELO verification was
12587 .cindex "DNS" "DNSSEC"
12588 done using DNS information the resolver library stated was authenticated data.
12590 .vitem &$sender_helo_name$&
12591 .vindex "&$sender_helo_name$&"
12592 When a message is received from a remote host that has issued a HELO or EHLO
12593 command, the argument of that command is placed in this variable. It is also
12594 set if HELO or EHLO is used when a message is received using SMTP locally via
12595 the &%-bs%& or &%-bS%& options.
12597 .vitem &$sender_host_address$&
12598 .vindex "&$sender_host_address$&"
12599 When a message is received from a remote host using SMTP,
12600 this variable contains that
12601 host's IP address. For locally non-SMTP submitted messages, it is empty.
12603 .vitem &$sender_host_authenticated$&
12604 .vindex "&$sender_host_authenticated$&"
12605 This variable contains the name (not the public name) of the authenticator
12606 driver that successfully authenticated the client from which the message was
12607 received. It is empty if there was no successful authentication. See also
12608 &$authenticated_id$&.
12610 .vitem &$sender_host_dnssec$&
12611 .vindex "&$sender_host_dnssec$&"
12612 If an attempt to populate &$sender_host_name$& has been made
12613 (by reference, &%hosts_lookup%& or
12614 otherwise) then this boolean will have been set true if, and only if, the
12615 resolver library states that both
12616 the reverse and forward DNS were authenticated data. At all
12617 other times, this variable is false.
12619 .cindex "DNS" "DNSSEC"
12620 It is likely that you will need to coerce DNSSEC support on in the resolver
12621 library, by setting:
12626 Exim does not perform DNSSEC validation itself, instead leaving that to a
12627 validating resolver (e.g. unbound, or bind with suitable configuration).
12629 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12630 mechanism in the list, then this variable will be false.
12632 This requires that your system resolver library support EDNS0 (and that
12633 DNSSEC flags exist in the system headers). If the resolver silently drops
12634 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
12635 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
12638 .vitem &$sender_host_name$&
12639 .vindex "&$sender_host_name$&"
12640 When a message is received from a remote host, this variable contains the
12641 host's name as obtained by looking up its IP address. For messages received by
12642 other means, this variable is empty.
12644 .vindex "&$host_lookup_failed$&"
12645 If the host name has not previously been looked up, a reference to
12646 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12647 A looked up name is accepted only if it leads back to the original IP address
12648 via a forward lookup. If either the reverse or the forward lookup fails to find
12649 any data, or if the forward lookup does not yield the original IP address,
12650 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12652 .vindex "&$host_lookup_deferred$&"
12653 However, if either of the lookups cannot be completed (for example, there is a
12654 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12655 &$host_lookup_failed$& remains set to &"0"&.
12657 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12658 host name again if there is a subsequent reference to &$sender_host_name$&
12659 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12662 Exim does not automatically look up every calling host's name. If you want
12663 maximum efficiency, you should arrange your configuration so that it avoids
12664 these lookups altogether. The lookup happens only if one or more of the
12665 following are true:
12668 A string containing &$sender_host_name$& is expanded.
12670 The calling host matches the list in &%host_lookup%&. In the default
12671 configuration, this option is set to *, so it must be changed if lookups are
12672 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12674 Exim needs the host name in order to test an item in a host list. The items
12675 that require this are described in sections &<<SECThoslispatnam>>& and
12676 &<<SECThoslispatnamsk>>&.
12678 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12679 In this case, the host name is required to compare with the name quoted in any
12680 EHLO or HELO commands that the client issues.
12682 The remote host issues a EHLO or HELO command that quotes one of the
12683 domains in &%helo_lookup_domains%&. The default value of this option is
12684 . ==== As this is a nested list, any displays it contains must be indented
12685 . ==== as otherwise they are too far to the left.
12687 helo_lookup_domains = @ : @[]
12689 which causes a lookup if a remote host (incorrectly) gives the server's name or
12690 IP address in an EHLO or HELO command.
12694 .vitem &$sender_host_port$&
12695 .vindex "&$sender_host_port$&"
12696 When a message is received from a remote host, this variable contains the port
12697 number that was used on the remote host.
12699 .vitem &$sender_ident$&
12700 .vindex "&$sender_ident$&"
12701 When a message is received from a remote host, this variable contains the
12702 identification received in response to an RFC 1413 request. When a message has
12703 been received locally, this variable contains the login name of the user that
12706 .vitem &$sender_rate_$&&'xxx'&
12707 A number of variables whose names begin &$sender_rate_$& are set as part of the
12708 &%ratelimit%& ACL condition. Details are given in section
12709 &<<SECTratelimiting>>&.
12711 .vitem &$sender_rcvhost$&
12712 .cindex "DNS" "reverse lookup"
12713 .cindex "reverse DNS lookup"
12714 .vindex "&$sender_rcvhost$&"
12715 This is provided specifically for use in &'Received:'& headers. It starts with
12716 either the verified host name (as obtained from a reverse DNS lookup) or, if
12717 there is no verified host name, the IP address in square brackets. After that
12718 there may be text in parentheses. When the first item is a verified host name,
12719 the first thing in the parentheses is the IP address in square brackets,
12720 followed by a colon and a port number if port logging is enabled. When the
12721 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12724 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12725 was used and its argument was not identical to the real host name or IP
12726 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12727 all three items are present in the parentheses, a newline and tab are inserted
12728 into the string, to improve the formatting of the &'Received:'& header.
12730 .vitem &$sender_verify_failure$&
12731 .vindex "&$sender_verify_failure$&"
12732 In an ACL, when a sender verification fails, this variable contains information
12733 about the failure. The details are the same as for
12734 &$recipient_verify_failure$&.
12736 .vitem &$sending_ip_address$&
12737 .vindex "&$sending_ip_address$&"
12738 This variable is set whenever an outgoing SMTP connection to another host has
12739 been set up. It contains the IP address of the local interface that is being
12740 used. This is useful if a host that has more than one IP address wants to take
12741 on different personalities depending on which one is being used. For incoming
12742 connections, see &$received_ip_address$&.
12744 .vitem &$sending_port$&
12745 .vindex "&$sending_port$&"
12746 This variable is set whenever an outgoing SMTP connection to another host has
12747 been set up. It contains the local port that is being used. For incoming
12748 connections, see &$received_port$&.
12750 .vitem &$smtp_active_hostname$&
12751 .vindex "&$smtp_active_hostname$&"
12752 During an incoming SMTP session, this variable contains the value of the active
12753 host name, as specified by the &%smtp_active_hostname%& option. The value of
12754 &$smtp_active_hostname$& is saved with any message that is received, so its
12755 value can be consulted during routing and delivery.
12757 .vitem &$smtp_command$&
12758 .vindex "&$smtp_command$&"
12759 During the processing of an incoming SMTP command, this variable contains the
12760 entire command. This makes it possible to distinguish between HELO and EHLO in
12761 the HELO ACL, and also to distinguish between commands such as these:
12766 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12767 command, the address in &$smtp_command$& is the original address before any
12768 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12769 the address after SMTP-time rewriting.
12771 .vitem &$smtp_command_argument$&
12772 .cindex "SMTP" "command, argument for"
12773 .vindex "&$smtp_command_argument$&"
12774 While an ACL is running to check an SMTP command, this variable contains the
12775 argument, that is, the text that follows the command name, with leading white
12776 space removed. Following the introduction of &$smtp_command$&, this variable is
12777 somewhat redundant, but is retained for backwards compatibility.
12779 .vitem &$smtp_count_at_connection_start$&
12780 .vindex "&$smtp_count_at_connection_start$&"
12781 This variable is set greater than zero only in processes spawned by the Exim
12782 daemon for handling incoming SMTP connections. The name is deliberately long,
12783 in order to emphasize what the contents are. When the daemon accepts a new
12784 connection, it increments this variable. A copy of the variable is passed to
12785 the child process that handles the connection, but its value is fixed, and
12786 never changes. It is only an approximation of how many incoming connections
12787 there actually are, because many other connections may come and go while a
12788 single connection is being processed. When a child process terminates, the
12789 daemon decrements its copy of the variable.
12791 .vitem "&$sn0$& &-- &$sn9$&"
12792 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12793 that were current at the end of the system filter file. This allows a system
12794 filter file to set values that can be tested in users' filter files. For
12795 example, a system filter could set a value indicating how likely it is that a
12796 message is junk mail.
12798 .vitem &$spam_$&&'xxx'&
12799 A number of variables whose names start with &$spam$& are available when Exim
12800 is compiled with the content-scanning extension. For details, see section
12801 &<<SECTscanspamass>>&.
12804 .vitem &$spool_directory$&
12805 .vindex "&$spool_directory$&"
12806 The name of Exim's spool directory.
12808 .vitem &$spool_inodes$&
12809 .vindex "&$spool_inodes$&"
12810 The number of free inodes in the disk partition where Exim's spool files are
12811 being written. The value is recalculated whenever the variable is referenced.
12812 If the relevant file system does not have the concept of inodes, the value of
12813 is -1. See also the &%check_spool_inodes%& option.
12815 .vitem &$spool_space$&
12816 .vindex "&$spool_space$&"
12817 The amount of free space (as a number of kilobytes) in the disk partition where
12818 Exim's spool files are being written. The value is recalculated whenever the
12819 variable is referenced. If the operating system does not have the ability to
12820 find the amount of free space (only true for experimental systems), the space
12821 value is -1. For example, to check in an ACL that there is at least 50
12822 megabytes free on the spool, you could write:
12824 condition = ${if > {$spool_space}{50000}}
12826 See also the &%check_spool_space%& option.
12829 .vitem &$thisaddress$&
12830 .vindex "&$thisaddress$&"
12831 This variable is set only during the processing of the &%foranyaddress%&
12832 command in a filter file. Its use is explained in the description of that
12833 command, which can be found in the separate document entitled &'Exim's
12834 interfaces to mail filtering'&.
12836 .vitem &$tls_in_bits$&
12837 .vindex "&$tls_in_bits$&"
12838 Contains an approximation of the TLS cipher's bit-strength
12839 on the inbound connection; the meaning of
12840 this depends upon the TLS implementation used.
12841 If TLS has not been negotiated, the value will be 0.
12842 The value of this is automatically fed into the Cyrus SASL authenticator
12843 when acting as a server, to specify the "external SSF" (a SASL term).
12845 The deprecated &$tls_bits$& variable refers to the inbound side
12846 except when used in the context of an outbound SMTP delivery, when it refers to
12849 .vitem &$tls_out_bits$&
12850 .vindex "&$tls_out_bits$&"
12851 Contains an approximation of the TLS cipher's bit-strength
12852 on an outbound SMTP connection; the meaning of
12853 this depends upon the TLS implementation used.
12854 If TLS has not been negotiated, the value will be 0.
12856 .vitem &$tls_in_ourcert$&
12857 .vindex "&$tls_in_ourcert$&"
12858 .cindex certificate variables
12859 This variable refers to the certificate presented to the peer of an
12860 inbound connection when the message was received.
12861 It is only useful as the argument of a
12862 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12863 or a &%def%& condition.
12865 .vitem &$tls_in_peercert$&
12866 .vindex "&$tls_in_peercert$&"
12867 This variable refers to the certificate presented by the peer of an
12868 inbound connection when the message was received.
12869 It is only useful as the argument of a
12870 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12871 or a &%def%& condition.
12872 If certificate verification fails it may refer to a failing chain element
12873 which is not the leaf.
12875 .vitem &$tls_out_ourcert$&
12876 .vindex "&$tls_out_ourcert$&"
12877 This variable refers to the certificate presented to the peer of an
12878 outbound connection. It is only useful as the argument of a
12879 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12880 or a &%def%& condition.
12882 .vitem &$tls_out_peercert$&
12883 .vindex "&$tls_out_peercert$&"
12884 This variable refers to the certificate presented by the peer of an
12885 outbound connection. It is only useful as the argument of a
12886 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12887 or a &%def%& condition.
12888 If certificate verification fails it may refer to a failing chain element
12889 which is not the leaf.
12891 .vitem &$tls_in_certificate_verified$&
12892 .vindex "&$tls_in_certificate_verified$&"
12893 This variable is set to &"1"& if a TLS certificate was verified when the
12894 message was received, and &"0"& otherwise.
12896 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
12897 except when used in the context of an outbound SMTP delivery, when it refers to
12900 .vitem &$tls_out_certificate_verified$&
12901 .vindex "&$tls_out_certificate_verified$&"
12902 This variable is set to &"1"& if a TLS certificate was verified when an
12903 outbound SMTP connection was made,
12904 and &"0"& otherwise.
12906 .vitem &$tls_in_cipher$&
12907 .vindex "&$tls_in_cipher$&"
12908 .vindex "&$tls_cipher$&"
12909 When a message is received from a remote host over an encrypted SMTP
12910 connection, this variable is set to the cipher suite that was negotiated, for
12911 example DES-CBC3-SHA. In other circumstances, in particular, for message
12912 received over unencrypted connections, the variable is empty. Testing
12913 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
12914 non-encrypted connections during ACL processing.
12916 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
12917 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
12918 becomes the same as &$tls_out_cipher$&.
12920 .vitem &$tls_out_cipher$&
12921 .vindex "&$tls_out_cipher$&"
12923 cleared before any outgoing SMTP connection is made,
12924 and then set to the outgoing cipher suite if one is negotiated. See chapter
12925 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
12926 details of the &(smtp)& transport.
12928 .vitem &$tls_in_ocsp$&
12929 .vindex "&$tls_in_ocsp$&"
12930 When a message is received from a remote client connection
12931 the result of any OCSP request from the client is encoded in this variable:
12933 0 OCSP proof was not requested (default value)
12934 1 No response to request
12935 2 Response not verified
12936 3 Verification failed
12937 4 Verification succeeded
12940 .vitem &$tls_out_ocsp$&
12941 .vindex "&$tls_out_ocsp$&"
12942 When a message is sent to a remote host connection
12943 the result of any OCSP request made is encoded in this variable.
12944 See &$tls_in_ocsp$& for values.
12946 .vitem &$tls_in_peerdn$&
12947 .vindex "&$tls_in_peerdn$&"
12948 .vindex "&$tls_peerdn$&"
12949 .cindex certificate "extracting fields"
12950 When a message is received from a remote host over an encrypted SMTP
12951 connection, and Exim is configured to request a certificate from the client,
12952 the value of the Distinguished Name of the certificate is made available in the
12953 &$tls_in_peerdn$& during subsequent processing.
12954 If certificate verification fails it may refer to a failing chain element
12955 which is not the leaf.
12957 The deprecated &$tls_peerdn$& variable refers to the inbound side
12958 except when used in the context of an outbound SMTP delivery, when it refers to
12961 .vitem &$tls_out_peerdn$&
12962 .vindex "&$tls_out_peerdn$&"
12963 When a message is being delivered to a remote host over an encrypted SMTP
12964 connection, and Exim is configured to request a certificate from the server,
12965 the value of the Distinguished Name of the certificate is made available in the
12966 &$tls_out_peerdn$& during subsequent processing.
12967 If certificate verification fails it may refer to a failing chain element
12968 which is not the leaf.
12970 .vitem &$tls_in_sni$&
12971 .vindex "&$tls_in_sni$&"
12972 .vindex "&$tls_sni$&"
12973 .cindex "TLS" "Server Name Indication"
12974 When a TLS session is being established, if the client sends the Server
12975 Name Indication extension, the value will be placed in this variable.
12976 If the variable appears in &%tls_certificate%& then this option and
12977 some others, described in &<<SECTtlssni>>&,
12978 will be re-expanded early in the TLS session, to permit
12979 a different certificate to be presented (and optionally a different key to be
12980 used) to the client, based upon the value of the SNI extension.
12982 The deprecated &$tls_sni$& variable refers to the inbound side
12983 except when used in the context of an outbound SMTP delivery, when it refers to
12986 .vitem &$tls_out_sni$&
12987 .vindex "&$tls_out_sni$&"
12988 .cindex "TLS" "Server Name Indication"
12990 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
12993 .vitem &$tod_bsdinbox$&
12994 .vindex "&$tod_bsdinbox$&"
12995 The time of day and the date, in the format required for BSD-style mailbox
12996 files, for example: Thu Oct 17 17:14:09 1995.
12998 .vitem &$tod_epoch$&
12999 .vindex "&$tod_epoch$&"
13000 The time and date as a number of seconds since the start of the Unix epoch.
13002 .vitem &$tod_epoch_l$&
13003 .vindex "&$tod_epoch_l$&"
13004 The time and date as a number of microseconds since the start of the Unix epoch.
13006 .vitem &$tod_full$&
13007 .vindex "&$tod_full$&"
13008 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13009 +0100. The timezone is always given as a numerical offset from UTC, with
13010 positive values used for timezones that are ahead (east) of UTC, and negative
13011 values for those that are behind (west).
13014 .vindex "&$tod_log$&"
13015 The time and date in the format used for writing Exim's log files, for example:
13016 1995-10-12 15:32:29, but without a timezone.
13018 .vitem &$tod_logfile$&
13019 .vindex "&$tod_logfile$&"
13020 This variable contains the date in the format yyyymmdd. This is the format that
13021 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13024 .vitem &$tod_zone$&
13025 .vindex "&$tod_zone$&"
13026 This variable contains the numerical value of the local timezone, for example:
13029 .vitem &$tod_zulu$&
13030 .vindex "&$tod_zulu$&"
13031 This variable contains the UTC date and time in &"Zulu"& format, as specified
13032 by ISO 8601, for example: 20030221154023Z.
13034 .vitem &$transport_name$&
13035 .cindex "transport" "name"
13036 .cindex "name" "of transport"
13037 .vindex "&$transport_name$&"
13038 During the running of a transport, this variable contains its name.
13041 .vindex "&$value$&"
13042 This variable contains the result of an expansion lookup, extraction operation,
13043 or external command, as described above. It is also used during a
13044 &*reduce*& expansion.
13046 .vitem &$verify_mode$&
13047 .vindex "&$verify_mode$&"
13048 While a router or transport is being run in verify mode or for cutthrough delivery,
13049 contains "S" for sender-verification or "R" for recipient-verification.
13052 .vitem &$version_number$&
13053 .vindex "&$version_number$&"
13054 The version number of Exim.
13056 .vitem &$warn_message_delay$&
13057 .vindex "&$warn_message_delay$&"
13058 This variable is set only during the creation of a message warning about a
13059 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13061 .vitem &$warn_message_recipients$&
13062 .vindex "&$warn_message_recipients$&"
13063 This variable is set only during the creation of a message warning about a
13064 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13070 . ////////////////////////////////////////////////////////////////////////////
13071 . ////////////////////////////////////////////////////////////////////////////
13073 .chapter "Embedded Perl" "CHAPperl"
13074 .scindex IIDperl "Perl" "calling from Exim"
13075 Exim can be built to include an embedded Perl interpreter. When this is done,
13076 Perl subroutines can be called as part of the string expansion process. To make
13077 use of the Perl support, you need version 5.004 or later of Perl installed on
13078 your system. To include the embedded interpreter in the Exim binary, include
13083 in your &_Local/Makefile_& and then build Exim in the normal way.
13086 .section "Setting up so Perl can be used" "SECID85"
13087 .oindex "&%perl_startup%&"
13088 Access to Perl subroutines is via a global configuration option called
13089 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13090 no &%perl_startup%& option in the Exim configuration file then no Perl
13091 interpreter is started and there is almost no overhead for Exim (since none of
13092 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13093 option then the associated value is taken to be Perl code which is executed in
13094 a newly created Perl interpreter.
13096 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13097 need backslashes before any characters to escape special meanings. The option
13098 should usually be something like
13100 perl_startup = do '/etc/exim.pl'
13102 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13103 use from Exim. Exim can be configured either to start up a Perl interpreter as
13104 soon as it is entered, or to wait until the first time it is needed. Starting
13105 the interpreter at the beginning ensures that it is done while Exim still has
13106 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13107 fact used in a particular run. Also, note that this does not mean that Exim is
13108 necessarily running as root when Perl is called at a later time. By default,
13109 the interpreter is started only when it is needed, but this can be changed in
13113 .oindex "&%perl_at_start%&"
13114 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13115 a startup when Exim is entered.
13117 The command line option &%-ps%& also requests a startup when Exim is entered,
13118 overriding the setting of &%perl_at_start%&.
13121 There is also a command line option &%-pd%& (for delay) which suppresses the
13122 initial startup, even if &%perl_at_start%& is set.
13125 .oindex "&%perl_taintmode%&"
13126 .cindex "Perl" "taintmode"
13127 To provide more security executing Perl code via the embedded Perl
13128 interpreter, the &%perl_taintmode%& option can be set. This enables the
13129 taint mode of the Perl interpreter. You are encouraged to set this
13130 option to a true value. To avoid breaking existing installations, it
13134 .section "Calling Perl subroutines" "SECID86"
13135 When the configuration file includes a &%perl_startup%& option you can make use
13136 of the string expansion item to call the Perl subroutines that are defined
13137 by the &%perl_startup%& code. The operator is used in any of the following
13141 ${perl{foo}{argument}}
13142 ${perl{foo}{argument1}{argument2} ... }
13144 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
13145 arguments may be passed. Passing more than this results in an expansion failure
13146 with an error message of the form
13148 Too many arguments passed to Perl subroutine "foo" (max is 8)
13150 The return value of the Perl subroutine is evaluated in a scalar context before
13151 it is passed back to Exim to be inserted into the expanded string. If the
13152 return value is &'undef'&, the expansion is forced to fail in the same way as
13153 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13154 by obeying Perl's &%die%& function, the expansion fails with the error message
13155 that was passed to &%die%&.
13158 .section "Calling Exim functions from Perl" "SECID87"
13159 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13160 is available to call back into Exim's string expansion function. For example,
13163 my $lp = Exim::expand_string('$local_part');
13165 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13166 Note those are single quotes and not double quotes to protect against
13167 &$local_part$& being interpolated as a Perl variable.
13169 If the string expansion is forced to fail by a &"fail"& item, the result of
13170 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13171 expansion string, the Perl call from the original expansion string fails with
13172 an appropriate error message, in the same way as if &%die%& were used.
13174 .cindex "debugging" "from embedded Perl"
13175 .cindex "log" "writing from embedded Perl"
13176 Two other Exim functions are available for use from within Perl code.
13177 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13178 debugging is enabled. If you want a newline at the end, you must supply it.
13179 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13180 timestamp. In this case, you should not supply a terminating newline.
13183 .section "Use of standard output and error by Perl" "SECID88"
13184 .cindex "Perl" "standard output and error"
13185 You should not write to the standard error or output streams from within your
13186 Perl code, as it is not defined how these are set up. In versions of Exim
13187 before 4.50, it is possible for the standard output or error to refer to the
13188 SMTP connection during message reception via the daemon. Writing to this stream
13189 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13190 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13191 avoided, but the output is lost.
13193 .cindex "Perl" "use of &%warn%&"
13194 The Perl &%warn%& statement writes to the standard error stream by default.
13195 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13196 you have no control. When Exim starts up the Perl interpreter, it arranges for
13197 output from the &%warn%& statement to be written to the Exim main log. You can
13198 change this by including appropriate Perl magic somewhere in your Perl code.
13199 For example, to discard &%warn%& output completely, you need this:
13201 $SIG{__WARN__} = sub { };
13203 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13204 example, the code for the subroutine is empty, so it does nothing, but you can
13205 include any Perl code that you like. The text of the &%warn%& message is passed
13206 as the first subroutine argument.
13210 . ////////////////////////////////////////////////////////////////////////////
13211 . ////////////////////////////////////////////////////////////////////////////
13213 .chapter "Starting the daemon and the use of network interfaces" &&&
13214 "CHAPinterfaces" &&&
13215 "Starting the daemon"
13216 .cindex "daemon" "starting"
13217 .cindex "interface" "listening"
13218 .cindex "network interface"
13219 .cindex "interface" "network"
13220 .cindex "IP address" "for listening"
13221 .cindex "daemon" "listening IP addresses"
13222 .cindex "TCP/IP" "setting listening interfaces"
13223 .cindex "TCP/IP" "setting listening ports"
13224 A host that is connected to a TCP/IP network may have one or more physical
13225 hardware network interfaces. Each of these interfaces may be configured as one
13226 or more &"logical"& interfaces, which are the entities that a program actually
13227 works with. Each of these logical interfaces is associated with an IP address.
13228 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13229 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13230 knowledge about the host's interfaces for use in three different circumstances:
13233 When a listening daemon is started, Exim needs to know which interfaces
13234 and ports to listen on.
13236 When Exim is routing an address, it needs to know which IP addresses
13237 are associated with local interfaces. This is required for the correct
13238 processing of MX lists by removing the local host and others with the
13239 same or higher priority values. Also, Exim needs to detect cases
13240 when an address is routed to an IP address that in fact belongs to the
13241 local host. Unless the &%self%& router option or the &%allow_localhost%&
13242 option of the smtp transport is set (as appropriate), this is treated
13243 as an error situation.
13245 When Exim connects to a remote host, it may need to know which interface to use
13246 for the outgoing connection.
13250 Exim's default behaviour is likely to be appropriate in the vast majority
13251 of cases. If your host has only one interface, and you want all its IP
13252 addresses to be treated in the same way, and you are using only the
13253 standard SMTP port, you should not need to take any special action. The
13254 rest of this chapter does not apply to you.
13256 In a more complicated situation you may want to listen only on certain
13257 interfaces, or on different ports, and for this reason there are a number of
13258 options that can be used to influence Exim's behaviour. The rest of this
13259 chapter describes how they operate.
13261 When a message is received over TCP/IP, the interface and port that were
13262 actually used are set in &$received_ip_address$& and &$received_port$&.
13266 .section "Starting a listening daemon" "SECID89"
13267 When a listening daemon is started (by means of the &%-bd%& command line
13268 option), the interfaces and ports on which it listens are controlled by the
13272 &%daemon_smtp_ports%& contains a list of default ports
13274 (For backward compatibility, this option can also be specified in the singular.)
13276 &%local_interfaces%& contains list of interface IP addresses on which to
13277 listen. Each item may optionally also specify a port.
13280 The default list separator in both cases is a colon, but this can be changed as
13281 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
13282 it is usually best to change the separator to avoid having to double all the
13283 colons. For example:
13285 local_interfaces = <; 127.0.0.1 ; \
13288 3ffe:ffff:836f::fe86:a061
13290 There are two different formats for specifying a port along with an IP address
13291 in &%local_interfaces%&:
13294 The port is added onto the address with a dot separator. For example, to listen
13295 on port 1234 on two different IP addresses:
13297 local_interfaces = <; 192.168.23.65.1234 ; \
13298 3ffe:ffff:836f::fe86:a061.1234
13301 The IP address is enclosed in square brackets, and the port is added
13302 with a colon separator, for example:
13304 local_interfaces = <; [192.168.23.65]:1234 ; \
13305 [3ffe:ffff:836f::fe86:a061]:1234
13309 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13310 default setting contains just one port:
13312 daemon_smtp_ports = smtp
13314 If more than one port is listed, each interface that does not have its own port
13315 specified listens on all of them. Ports that are listed in
13316 &%daemon_smtp_ports%& can be identified either by name (defined in
13317 &_/etc/services_&) or by number. However, when ports are given with individual
13318 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13322 .section "Special IP listening addresses" "SECID90"
13323 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13324 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13325 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13326 instead of setting up separate listening sockets for each interface. The
13327 default value of &%local_interfaces%& is
13329 local_interfaces = 0.0.0.0
13331 when Exim is built without IPv6 support; otherwise it is:
13333 local_interfaces = <; ::0 ; 0.0.0.0
13335 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13339 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13340 The &%-oX%& command line option can be used to override the values of
13341 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13342 instance. Another way of doing this would be to use macros and the &%-D%&
13343 option. However, &%-oX%& can be used by any admin user, whereas modification of
13344 the runtime configuration by &%-D%& is allowed only when the caller is root or
13347 The value of &%-oX%& is a list of items. The default colon separator can be
13348 changed in the usual way if required. If there are any items that do not
13349 contain dots or colons (that is, are not IP addresses), the value of
13350 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13351 items that do contain dots or colons, the value of &%local_interfaces%& is
13352 replaced by those items. Thus, for example,
13356 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13359 -oX 192.168.34.5.1125
13361 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13362 (However, since &%local_interfaces%& now contains no items without ports, the
13363 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13367 .section "Support for the obsolete SSMTP (or SMTPS) protocol" "SECTsupobssmt"
13368 .cindex "ssmtp protocol"
13369 .cindex "smtps protocol"
13370 .cindex "SMTP" "ssmtp protocol"
13371 .cindex "SMTP" "smtps protocol"
13372 Exim supports the obsolete SSMTP protocol (also known as SMTPS) that was used
13373 before the STARTTLS command was standardized for SMTP. Some legacy clients
13374 still use this protocol. If the &%tls_on_connect_ports%& option is set to a
13375 list of port numbers or service names,
13376 connections to those ports must use SSMTP. The most
13377 common use of this option is expected to be
13379 tls_on_connect_ports = 465
13381 because 465 is the usual port number used by the legacy clients. There is also
13382 a command line option &%-tls-on-connect%&, which forces all ports to behave in
13383 this way when a daemon is started.
13385 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13386 daemon to listen on those ports. You must still specify them in
13387 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13388 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13389 connections via the daemon.)
13394 .section "IPv6 address scopes" "SECID92"
13395 .cindex "IPv6" "address scopes"
13396 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13397 can, in principle, have the same link-local IPv6 address on different
13398 interfaces. Thus, additional information is needed, over and above the IP
13399 address, to distinguish individual interfaces. A convention of using a
13400 percent sign followed by something (often the interface name) has been
13401 adopted in some cases, leading to addresses like this:
13403 fe80::202:b3ff:fe03:45c1%eth0
13405 To accommodate this usage, a percent sign followed by an arbitrary string is
13406 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13407 to convert a textual IPv6 address for actual use. This function recognizes the
13408 percent convention in operating systems that support it, and it processes the
13409 address appropriately. Unfortunately, some older libraries have problems with
13410 &[getaddrinfo()]&. If
13412 IPV6_USE_INET_PTON=yes
13414 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13415 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13416 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13417 function.) Of course, this means that the additional functionality of
13418 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13420 .section "Disabling IPv6" "SECID93"
13421 .cindex "IPv6" "disabling"
13422 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13423 run on a host whose kernel does not support IPv6. The binary will fall back to
13424 using IPv4, but it may waste resources looking up AAAA records, and trying to
13425 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13426 .oindex "&%disable_ipv6%&"
13427 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13428 activities take place. AAAA records are never looked up, and any IPv6 addresses
13429 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13430 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13431 to handle IPv6 literal addresses.
13433 On the other hand, when IPv6 is in use, there may be times when you want to
13434 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13435 option to globally suppress the lookup of AAAA records for specified domains,
13436 and you can use the &%ignore_target_hosts%& generic router option to ignore
13437 IPv6 addresses in an individual router.
13441 .section "Examples of starting a listening daemon" "SECID94"
13442 The default case in an IPv6 environment is
13444 daemon_smtp_ports = smtp
13445 local_interfaces = <; ::0 ; 0.0.0.0
13447 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13448 Either one or two sockets may be used, depending on the characteristics of
13449 the TCP/IP stack. (This is complicated and messy; for more information,
13450 read the comments in the &_daemon.c_& source file.)
13452 To specify listening on ports 25 and 26 on all interfaces:
13454 daemon_smtp_ports = 25 : 26
13456 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13458 local_interfaces = <; ::0.25 ; ::0.26 \
13459 0.0.0.0.25 ; 0.0.0.0.26
13461 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13462 IPv4 loopback address only:
13464 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13466 To specify listening on the default port on specific interfaces only:
13468 local_interfaces = 10.0.0.67 : 192.168.34.67
13470 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13474 .section "Recognizing the local host" "SECTreclocipadd"
13475 The &%local_interfaces%& option is also used when Exim needs to determine
13476 whether or not an IP address refers to the local host. That is, the IP
13477 addresses of all the interfaces on which a daemon is listening are always
13480 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13481 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13482 available interfaces from the operating system, and extracts the relevant
13483 (that is, IPv4 or IPv6) addresses to use for checking.
13485 Some systems set up large numbers of virtual interfaces in order to provide
13486 many virtual web servers. In this situation, you may want to listen for
13487 email on only a few of the available interfaces, but nevertheless treat all
13488 interfaces as local when routing. You can do this by setting
13489 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13490 &"all"& wildcard values. These addresses are recognized as local, but are not
13491 used for listening. Consider this example:
13493 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13495 3ffe:2101:12:1:a00:20ff:fe86:a061
13497 extra_local_interfaces = <; ::0 ; 0.0.0.0
13499 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13500 address, but all available interface addresses are treated as local when
13503 In some environments the local host name may be in an MX list, but with an IP
13504 address that is not assigned to any local interface. In other cases it may be
13505 desirable to treat other host names as if they referred to the local host. Both
13506 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13507 This contains host names rather than IP addresses. When a host is referenced
13508 during routing, either via an MX record or directly, it is treated as the local
13509 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13510 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13514 .section "Delivering to a remote host" "SECID95"
13515 Delivery to a remote host is handled by the smtp transport. By default, it
13516 allows the system's TCP/IP functions to choose which interface to use (if
13517 there is more than one) when connecting to a remote host. However, the
13518 &%interface%& option can be set to specify which interface is used. See the
13519 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13525 . ////////////////////////////////////////////////////////////////////////////
13526 . ////////////////////////////////////////////////////////////////////////////
13528 .chapter "Main configuration" "CHAPmainconfig"
13529 .scindex IIDconfima "configuration file" "main section"
13530 .scindex IIDmaiconf "main configuration"
13531 The first part of the run time configuration file contains three types of item:
13534 Macro definitions: These lines start with an upper case letter. See section
13535 &<<SECTmacrodefs>>& for details of macro processing.
13537 Named list definitions: These lines start with one of the words &"domainlist"&,
13538 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13539 section &<<SECTnamedlists>>&.
13541 Main configuration settings: Each setting occupies one line of the file
13542 (with possible continuations). If any setting is preceded by the word
13543 &"hide"&, the &%-bP%& command line option displays its value to admin users
13544 only. See section &<<SECTcos>>& for a description of the syntax of these option
13548 This chapter specifies all the main configuration options, along with their
13549 types and default values. For ease of finding a particular option, they appear
13550 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13551 are now so many options, they are first listed briefly in functional groups, as
13552 an aid to finding the name of the option you are looking for. Some options are
13553 listed in more than one group.
13555 .section "Miscellaneous" "SECID96"
13557 .row &%bi_command%& "to run for &%-bi%& command line option"
13558 .row &%debug_store%& "do extra internal checks"
13559 .row &%disable_ipv6%& "do no IPv6 processing"
13560 .row &%keep_malformed%& "for broken files &-- should not happen"
13561 .row &%localhost_number%& "for unique message ids in clusters"
13562 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13563 .row &%message_body_visible%& "how much to show in &$message_body$&"
13564 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13565 .row &%print_topbitchars%& "top-bit characters are printing"
13566 .row &%timezone%& "force time zone"
13570 .section "Exim parameters" "SECID97"
13572 .row &%exim_group%& "override compiled-in value"
13573 .row &%exim_path%& "override compiled-in value"
13574 .row &%exim_user%& "override compiled-in value"
13575 .row &%primary_hostname%& "default from &[uname()]&"
13576 .row &%split_spool_directory%& "use multiple directories"
13577 .row &%spool_directory%& "override compiled-in value"
13582 .section "Privilege controls" "SECID98"
13584 .row &%admin_groups%& "groups that are Exim admin users"
13585 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13586 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13587 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13588 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13589 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13590 .row &%never_users%& "do not run deliveries as these"
13591 .row &%prod_requires_admin%& "forced delivery requires admin user"
13592 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13593 .row &%trusted_groups%& "groups that are trusted"
13594 .row &%trusted_users%& "users that are trusted"
13599 .section "Logging" "SECID99"
13601 .row &%event_action%& "custom logging"
13602 .row &%hosts_connection_nolog%& "exemption from connect logging"
13603 .row &%log_file_path%& "override compiled-in value"
13604 .row &%log_selector%& "set/unset optional logging"
13605 .row &%log_timezone%& "add timezone to log lines"
13606 .row &%message_logs%& "create per-message logs"
13607 .row &%preserve_message_logs%& "after message completion"
13608 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13609 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13610 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13611 .row &%syslog_facility%& "set syslog &""facility""& field"
13612 .row &%syslog_pid%& "pid in syslog lines"
13613 .row &%syslog_processname%& "set syslog &""ident""& field"
13614 .row &%syslog_timestamp%& "timestamp syslog lines"
13615 .row &%write_rejectlog%& "control use of message log"
13620 .section "Frozen messages" "SECID100"
13622 .row &%auto_thaw%& "sets time for retrying frozen messages"
13623 .row &%freeze_tell%& "send message when freezing"
13624 .row &%move_frozen_messages%& "to another directory"
13625 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13630 .section "Data lookups" "SECID101"
13632 .row &%ibase_servers%& "InterBase servers"
13633 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13634 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13635 .row &%ldap_cert_file%& "client cert file for LDAP"
13636 .row &%ldap_cert_key%& "client key file for LDAP"
13637 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13638 .row &%ldap_default_servers%& "used if no server in query"
13639 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13640 .row &%ldap_start_tls%& "require TLS within LDAP"
13641 .row &%ldap_version%& "set protocol version"
13642 .row &%lookup_open_max%& "lookup files held open"
13643 .row &%mysql_servers%& "default MySQL servers"
13644 .row &%oracle_servers%& "Oracle servers"
13645 .row &%pgsql_servers%& "default PostgreSQL servers"
13646 .row &%sqlite_lock_timeout%& "as it says"
13651 .section "Message ids" "SECID102"
13653 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13654 .row &%message_id_header_text%& "ditto"
13659 .section "Embedded Perl Startup" "SECID103"
13661 .row &%perl_at_start%& "always start the interpreter"
13662 .row &%perl_startup%& "code to obey when starting Perl"
13663 .row &%perl_taintmode%& "enable taint mode in Perl"
13668 .section "Daemon" "SECID104"
13670 .row &%daemon_smtp_ports%& "default ports"
13671 .row &%daemon_startup_retries%& "number of times to retry"
13672 .row &%daemon_startup_sleep%& "time to sleep between tries"
13673 .row &%extra_local_interfaces%& "not necessarily listened on"
13674 .row &%local_interfaces%& "on which to listen, with optional ports"
13675 .row &%pid_file_path%& "override compiled-in value"
13676 .row &%queue_run_max%& "maximum simultaneous queue runners"
13681 .section "Resource control" "SECID105"
13683 .row &%check_log_inodes%& "before accepting a message"
13684 .row &%check_log_space%& "before accepting a message"
13685 .row &%check_spool_inodes%& "before accepting a message"
13686 .row &%check_spool_space%& "before accepting a message"
13687 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13688 .row &%queue_only_load%& "queue incoming if load high"
13689 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13690 .row &%queue_run_max%& "maximum simultaneous queue runners"
13691 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13692 .row &%smtp_accept_max%& "simultaneous incoming connections"
13693 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13694 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13695 .row &%smtp_accept_max_per_connection%& "messages per connection"
13696 .row &%smtp_accept_max_per_host%& "connections from one host"
13697 .row &%smtp_accept_queue%& "queue mail if more connections"
13698 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13700 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13701 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13702 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13703 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13704 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13709 .section "Policy controls" "SECID106"
13711 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13712 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13713 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13714 .row &%acl_smtp_auth%& "ACL for AUTH"
13715 .row &%acl_smtp_connect%& "ACL for connection"
13716 .row &%acl_smtp_data%& "ACL for DATA"
13717 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13718 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13719 .row &%acl_smtp_etrn%& "ACL for ETRN"
13720 .row &%acl_smtp_expn%& "ACL for EXPN"
13721 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13722 .row &%acl_smtp_mail%& "ACL for MAIL"
13723 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13724 .row &%acl_smtp_mime%& "ACL for MIME parts"
13725 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13726 .row &%acl_smtp_predata%& "ACL for start of data"
13727 .row &%acl_smtp_quit%& "ACL for QUIT"
13728 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13729 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13730 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13731 .row &%av_scanner%& "specify virus scanner"
13732 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13734 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13735 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13736 .row &%header_maxsize%& "total size of message header"
13737 .row &%header_line_maxsize%& "individual header line limit"
13738 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13739 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13740 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13741 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13742 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13743 .row &%host_lookup%& "host name looked up for these hosts"
13744 .row &%host_lookup_order%& "order of DNS and local name lookups"
13745 .row &%hosts_proxy%& "use proxy protocol for these hosts"
13746 .row &%host_reject_connection%& "reject connection from these hosts"
13747 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13748 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13749 .row &%message_size_limit%& "for all messages"
13750 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13751 .row &%spamd_address%& "set interface to SpamAssassin"
13752 .row &%strict_acl_vars%& "object to unset ACL variables"
13757 .section "Callout cache" "SECID107"
13759 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13761 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13763 .row &%callout_negative_expire%& "timeout for negative address cache item"
13764 .row &%callout_positive_expire%& "timeout for positive address cache item"
13765 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13770 .section "TLS" "SECID108"
13772 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13773 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13774 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13775 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13776 .row &%tls_certificate%& "location of server certificate"
13777 .row &%tls_crl%& "certificate revocation list"
13778 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13779 .row &%tls_dhparam%& "DH parameters for server"
13780 .row &%tls_eccurve%& "EC curve selection for server"
13781 .row &%tls_ocsp_file%& "location of server certificate status proof"
13782 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13783 .row &%tls_privatekey%& "location of server private key"
13784 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13785 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13786 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13787 .row &%tls_verify_certificates%& "expected client certificates"
13788 .row &%tls_verify_hosts%& "insist on client certificate verify"
13793 .section "Local user handling" "SECID109"
13795 .row &%finduser_retries%& "useful in NIS environments"
13796 .row &%gecos_name%& "used when creating &'Sender:'&"
13797 .row &%gecos_pattern%& "ditto"
13798 .row &%max_username_length%& "for systems that truncate"
13799 .row &%unknown_login%& "used when no login name found"
13800 .row &%unknown_username%& "ditto"
13801 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13802 .row &%uucp_from_sender%& "ditto"
13807 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13809 .row &%header_maxsize%& "total size of message header"
13810 .row &%header_line_maxsize%& "individual header line limit"
13811 .row &%message_size_limit%& "applies to all messages"
13812 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13813 .row &%received_header_text%& "expanded to make &'Received:'&"
13814 .row &%received_headers_max%& "for mail loop detection"
13815 .row &%recipients_max%& "limit per message"
13816 .row &%recipients_max_reject%& "permanently reject excess recipients"
13822 .section "Non-SMTP incoming messages" "SECID111"
13824 .row &%receive_timeout%& "for non-SMTP messages"
13831 .section "Incoming SMTP messages" "SECID112"
13832 See also the &'Policy controls'& section above.
13835 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13836 .row &%host_lookup%& "host name looked up for these hosts"
13837 .row &%host_lookup_order%& "order of DNS and local name lookups"
13838 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13839 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13840 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13841 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13842 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13843 .row &%smtp_accept_max%& "simultaneous incoming connections"
13844 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13845 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13846 .row &%smtp_accept_max_per_connection%& "messages per connection"
13847 .row &%smtp_accept_max_per_host%& "connections from one host"
13848 .row &%smtp_accept_queue%& "queue mail if more connections"
13849 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13851 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13852 .row &%smtp_active_hostname%& "host name to use in messages"
13853 .row &%smtp_banner%& "text for welcome banner"
13854 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13855 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13856 .row &%smtp_enforce_sync%& "of SMTP command/responses"
13857 .row &%smtp_etrn_command%& "what to run for ETRN"
13858 .row &%smtp_etrn_serialize%& "only one at once"
13859 .row &%smtp_load_reserve%& "only reserve hosts if this load"
13860 .row &%smtp_max_unknown_commands%& "before dropping connection"
13861 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
13862 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
13863 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
13864 .row &%smtp_receive_timeout%& "per command or data line"
13865 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13866 .row &%smtp_return_error_details%& "give detail on rejections"
13871 .section "SMTP extensions" "SECID113"
13873 .row &%accept_8bitmime%& "advertise 8BITMIME"
13874 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
13875 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
13876 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
13877 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
13878 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
13879 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
13880 .row &%prdr_enable%& "advertise PRDR to all hosts"
13881 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
13882 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13887 .section "Processing messages" "SECID114"
13889 .row &%allow_domain_literals%& "recognize domain literal syntax"
13890 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
13891 .row &%allow_utf8_domains%& "in addresses"
13892 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13894 .row &%delivery_date_remove%& "from incoming messages"
13895 .row &%envelope_to_remove%& "from incoming messages"
13896 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
13897 .row &%headers_charset%& "default for translations"
13898 .row &%qualify_domain%& "default for senders"
13899 .row &%qualify_recipient%& "default for recipients"
13900 .row &%return_path_remove%& "from incoming messages"
13901 .row &%strip_excess_angle_brackets%& "in addresses"
13902 .row &%strip_trailing_dot%& "at end of addresses"
13903 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
13908 .section "System filter" "SECID115"
13910 .row &%system_filter%& "locate system filter"
13911 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
13913 .row &%system_filter_file_transport%& "transport for delivery to a file"
13914 .row &%system_filter_group%& "group for filter running"
13915 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
13916 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
13917 .row &%system_filter_user%& "user for filter running"
13922 .section "Routing and delivery" "SECID116"
13924 .row &%disable_ipv6%& "do no IPv6 processing"
13925 .row &%dns_again_means_nonexist%& "for broken domains"
13926 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
13927 .row &%dns_dnssec_ok%& "parameter for resolver"
13928 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
13929 .row &%dns_retrans%& "parameter for resolver"
13930 .row &%dns_retry%& "parameter for resolver"
13931 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
13932 .row &%dns_use_edns0%& "parameter for resolver"
13933 .row &%hold_domains%& "hold delivery for these domains"
13934 .row &%local_interfaces%& "for routing checks"
13935 .row &%queue_domains%& "no immediate delivery for these"
13936 .row &%queue_only%& "no immediate delivery at all"
13937 .row &%queue_only_file%& "no immediate delivery if file exists"
13938 .row &%queue_only_load%& "no immediate delivery if load is high"
13939 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13940 .row &%queue_only_override%& "allow command line to override"
13941 .row &%queue_run_in_order%& "order of arrival"
13942 .row &%queue_run_max%& "of simultaneous queue runners"
13943 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
13944 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13945 .row &%remote_sort_domains%& "order of remote deliveries"
13946 .row &%retry_data_expire%& "timeout for retry data"
13947 .row &%retry_interval_max%& "safety net for retry rules"
13952 .section "Bounce and warning messages" "SECID117"
13954 .row &%bounce_message_file%& "content of bounce"
13955 .row &%bounce_message_text%& "content of bounce"
13956 .row &%bounce_return_body%& "include body if returning message"
13957 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
13958 .row &%bounce_return_message%& "include original message in bounce"
13959 .row &%bounce_return_size_limit%& "limit on returned message"
13960 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
13961 .row &%dsn_from%& "set &'From:'& contents in bounces"
13962 .row &%errors_copy%& "copy bounce messages"
13963 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
13964 .row &%delay_warning%& "time schedule"
13965 .row &%delay_warning_condition%& "condition for warning messages"
13966 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
13967 .row &%smtp_return_error_details%& "give detail on rejections"
13968 .row &%warn_message_file%& "content of warning message"
13973 .section "Alphabetical list of main options" "SECTalomo"
13974 Those options that undergo string expansion before use are marked with
13977 .option accept_8bitmime main boolean true
13979 .cindex "8-bit characters"
13980 .cindex "log" "selectors"
13981 .cindex "log" "8BITMIME"
13982 This option causes Exim to send 8BITMIME in its response to an SMTP
13983 EHLO command, and to accept the BODY= parameter on MAIL commands.
13984 However, though Exim is 8-bit clean, it is not a protocol converter, and it
13985 takes no steps to do anything special with messages received by this route.
13987 Historically Exim kept this option off by default, but the maintainers
13988 feel that in today's Internet, this causes more problems than it solves.
13989 It now defaults to true.
13990 A more detailed analysis of the issues is provided by Dan Bernstein:
13992 &url(http://cr.yp.to/smtp/8bitmime.html)
13995 To log received 8BITMIME status use
13997 log_selector = +8bitmime
14000 .option acl_not_smtp main string&!! unset
14001 .cindex "&ACL;" "for non-SMTP messages"
14002 .cindex "non-SMTP messages" "ACLs for"
14003 This option defines the ACL that is run when a non-SMTP message has been
14004 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14007 .option acl_not_smtp_mime main string&!! unset
14008 This option defines the ACL that is run for individual MIME parts of non-SMTP
14009 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14012 .option acl_not_smtp_start main string&!! unset
14013 .cindex "&ACL;" "at start of non-SMTP message"
14014 .cindex "non-SMTP messages" "ACLs for"
14015 This option defines the ACL that is run before Exim starts reading a
14016 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14018 .option acl_smtp_auth main string&!! unset
14019 .cindex "&ACL;" "setting up for SMTP commands"
14020 .cindex "AUTH" "ACL for"
14021 This option defines the ACL that is run when an SMTP AUTH command is
14022 received. See chapter &<<CHAPACL>>& for further details.
14024 .option acl_smtp_connect main string&!! unset
14025 .cindex "&ACL;" "on SMTP connection"
14026 This option defines the ACL that is run when an SMTP connection is received.
14027 See chapter &<<CHAPACL>>& for further details.
14029 .option acl_smtp_data main string&!! unset
14030 .cindex "DATA" "ACL for"
14031 This option defines the ACL that is run after an SMTP DATA command has been
14032 processed and the message itself has been received, but before the final
14033 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14035 .option acl_smtp_data_prdr main string&!! accept
14036 .cindex "PRDR" "ACL for"
14037 .cindex "DATA" "PRDR ACL for"
14038 .cindex "&ACL;" "PRDR-related"
14039 .cindex "&ACL;" "per-user data processing"
14040 This option defines the ACL that,
14041 if the PRDR feature has been negotiated,
14042 is run for each recipient after an SMTP DATA command has been
14043 processed and the message itself has been received, but before the
14044 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14046 .option acl_smtp_dkim main string&!! unset
14047 .cindex DKIM "ACL for"
14048 This option defines the ACL that is run for each DKIM signature
14049 (by default, or as specified in the dkim_verify_signers option)
14050 of a received message.
14051 See chapter &<<CHAPdkim>>& for further details.
14053 .option acl_smtp_etrn main string&!! unset
14054 .cindex "ETRN" "ACL for"
14055 This option defines the ACL that is run when an SMTP ETRN command is
14056 received. See chapter &<<CHAPACL>>& for further details.
14058 .option acl_smtp_expn main string&!! unset
14059 .cindex "EXPN" "ACL for"
14060 This option defines the ACL that is run when an SMTP EXPN command is
14061 received. See chapter &<<CHAPACL>>& for further details.
14063 .option acl_smtp_helo main string&!! unset
14064 .cindex "EHLO" "ACL for"
14065 .cindex "HELO" "ACL for"
14066 This option defines the ACL that is run when an SMTP EHLO or HELO
14067 command is received. See chapter &<<CHAPACL>>& for further details.
14070 .option acl_smtp_mail main string&!! unset
14071 .cindex "MAIL" "ACL for"
14072 This option defines the ACL that is run when an SMTP MAIL command is
14073 received. See chapter &<<CHAPACL>>& for further details.
14075 .option acl_smtp_mailauth main string&!! unset
14076 .cindex "AUTH" "on MAIL command"
14077 This option defines the ACL that is run when there is an AUTH parameter on
14078 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14079 &<<CHAPSMTPAUTH>>& for details of authentication.
14081 .option acl_smtp_mime main string&!! unset
14082 .cindex "MIME content scanning" "ACL for"
14083 This option is available when Exim is built with the content-scanning
14084 extension. It defines the ACL that is run for each MIME part in a message. See
14085 section &<<SECTscanmimepart>>& for details.
14087 .option acl_smtp_notquit main string&!! unset
14088 .cindex "not-QUIT, ACL for"
14089 This option defines the ACL that is run when an SMTP session
14090 ends without a QUIT command being received.
14091 See chapter &<<CHAPACL>>& for further details.
14093 .option acl_smtp_predata main string&!! unset
14094 This option defines the ACL that is run when an SMTP DATA command is
14095 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14098 .option acl_smtp_quit main string&!! unset
14099 .cindex "QUIT, ACL for"
14100 This option defines the ACL that is run when an SMTP QUIT command is
14101 received. See chapter &<<CHAPACL>>& for further details.
14103 .option acl_smtp_rcpt main string&!! unset
14104 .cindex "RCPT" "ACL for"
14105 This option defines the ACL that is run when an SMTP RCPT command is
14106 received. See chapter &<<CHAPACL>>& for further details.
14108 .option acl_smtp_starttls main string&!! unset
14109 .cindex "STARTTLS, ACL for"
14110 This option defines the ACL that is run when an SMTP STARTTLS command is
14111 received. See chapter &<<CHAPACL>>& for further details.
14113 .option acl_smtp_vrfy main string&!! unset
14114 .cindex "VRFY" "ACL for"
14115 This option defines the ACL that is run when an SMTP VRFY command is
14116 received. See chapter &<<CHAPACL>>& for further details.
14118 .option add_environment main "string list" empty
14119 .cindex "environment" "set values"
14120 This option allows to set individual environment variables that the
14121 currently linked libraries and programs in child processes use.
14122 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
14124 .option admin_groups main "string list&!!" unset
14125 .cindex "admin user"
14126 This option is expanded just once, at the start of Exim's processing. If the
14127 current group or any of the supplementary groups of an Exim caller is in this
14128 colon-separated list, the caller has admin privileges. If all your system
14129 programmers are in a specific group, for example, you can give them all Exim
14130 admin privileges by putting that group in &%admin_groups%&. However, this does
14131 not permit them to read Exim's spool files (whose group owner is the Exim gid).
14132 To permit this, you have to add individuals to the Exim group.
14134 .option allow_domain_literals main boolean false
14135 .cindex "domain literal"
14136 If this option is set, the RFC 2822 domain literal format is permitted in
14137 email addresses. The option is not set by default, because the domain literal
14138 format is not normally required these days, and few people know about it. It
14139 has, however, been exploited by mail abusers.
14141 Unfortunately, it seems that some DNS black list maintainers are using this
14142 format to report black listing to postmasters. If you want to accept messages
14143 addressed to your hosts by IP address, you need to set
14144 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
14145 domains (defined in the named domain list &%local_domains%& in the default
14146 configuration). This &"magic string"& matches the domain literal form of all
14147 the local host's IP addresses.
14150 .option allow_mx_to_ip main boolean false
14151 .cindex "MX record" "pointing to IP address"
14152 It appears that more and more DNS zone administrators are breaking the rules
14153 and putting domain names that look like IP addresses on the right hand side of
14154 MX records. Exim follows the rules and rejects this, giving an error message
14155 that explains the misconfiguration. However, some other MTAs support this
14156 practice, so to avoid &"Why can't Exim do this?"& complaints,
14157 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14158 recommended, except when you have no other choice.
14160 .option allow_utf8_domains main boolean false
14161 .cindex "domain" "UTF-8 characters in"
14162 .cindex "UTF-8" "in domain name"
14163 Lots of discussion is going on about internationalized domain names. One
14164 camp is strongly in favour of just using UTF-8 characters, and it seems
14165 that at least two other MTAs permit this. This option allows Exim users to
14166 experiment if they wish.
14168 If it is set true, Exim's domain parsing function allows valid
14169 UTF-8 multicharacters to appear in domain name components, in addition to
14170 letters, digits, and hyphens. However, just setting this option is not
14171 enough; if you want to look up these domain names in the DNS, you must also
14172 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14173 suitable setting is:
14175 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14176 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14178 Alternatively, you can just disable this feature by setting
14180 dns_check_names_pattern =
14182 That is, set the option to an empty string so that no check is done.
14185 .option auth_advertise_hosts main "host list&!!" *
14186 .cindex "authentication" "advertising"
14187 .cindex "AUTH" "advertising"
14188 If any server authentication mechanisms are configured, Exim advertises them in
14189 response to an EHLO command only if the calling host matches this list.
14190 Otherwise, Exim does not advertise AUTH.
14191 Exim does not accept AUTH commands from clients to which it has not
14192 advertised the availability of AUTH. The advertising of individual
14193 authentication mechanisms can be controlled by the use of the
14194 &%server_advertise_condition%& generic authenticator option on the individual
14195 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14197 Certain mail clients (for example, Netscape) require the user to provide a name
14198 and password for authentication if AUTH is advertised, even though it may
14199 not be needed (the host may accept messages from hosts on its local LAN without
14200 authentication, for example). The &%auth_advertise_hosts%& option can be used
14201 to make these clients more friendly by excluding them from the set of hosts to
14202 which Exim advertises AUTH.
14204 .cindex "AUTH" "advertising when encrypted"
14205 If you want to advertise the availability of AUTH only when the connection
14206 is encrypted using TLS, you can make use of the fact that the value of this
14207 option is expanded, with a setting like this:
14209 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14211 .vindex "&$tls_in_cipher$&"
14212 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14213 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14214 expansion is *, which matches all hosts.
14217 .option auto_thaw main time 0s
14218 .cindex "thawing messages"
14219 .cindex "unfreezing messages"
14220 If this option is set to a time greater than zero, a queue runner will try a
14221 new delivery attempt on any frozen message, other than a bounce message, if
14222 this much time has passed since it was frozen. This may result in the message
14223 being re-frozen if nothing has changed since the last attempt. It is a way of
14224 saying &"keep on trying, even though there are big problems"&.
14226 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14227 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14228 thought to be very useful any more, and its use should probably be avoided.
14231 .option av_scanner main string "see below"
14232 This option is available if Exim is built with the content-scanning extension.
14233 It specifies which anti-virus scanner to use. The default value is:
14235 sophie:/var/run/sophie
14237 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14238 before use. See section &<<SECTscanvirus>>& for further details.
14241 .option bi_command main string unset
14243 This option supplies the name of a command that is run when Exim is called with
14244 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14245 just the command name, it is not a complete command line. If an argument is
14246 required, it must come from the &%-oA%& command line option.
14249 .option bounce_message_file main string unset
14250 .cindex "bounce message" "customizing"
14251 .cindex "customizing" "bounce message"
14252 This option defines a template file containing paragraphs of text to be used
14253 for constructing bounce messages. Details of the file's contents are given in
14254 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14257 .option bounce_message_text main string unset
14258 When this option is set, its contents are included in the default bounce
14259 message immediately after &"This message was created automatically by mail
14260 delivery software."& It is not used if &%bounce_message_file%& is set.
14262 .option bounce_return_body main boolean true
14263 .cindex "bounce message" "including body"
14264 This option controls whether the body of an incoming message is included in a
14265 bounce message when &%bounce_return_message%& is true. The default setting
14266 causes the entire message, both header and body, to be returned (subject to the
14267 value of &%bounce_return_size_limit%&). If this option is false, only the
14268 message header is included. In the case of a non-SMTP message containing an
14269 error that is detected during reception, only those header lines preceding the
14270 point at which the error was detected are returned.
14271 .cindex "bounce message" "including original"
14273 .option bounce_return_linesize_limit main integer 998
14274 .cindex "size" "of bounce lines, limit"
14275 .cindex "bounce message" "line length limit"
14276 .cindex "limit" "bounce message line length"
14277 This option sets a limit in bytes on the line length of messages
14278 that are returned to senders due to delivery problems,
14279 when &%bounce_return_message%& is true.
14280 The default value corresponds to RFC limits.
14281 If the message being returned has lines longer than this value it is
14282 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14284 The option also applies to bounces returned when an error is detected
14285 during reception of a message.
14286 In this case lines from the original are truncated.
14288 The option does not apply to messages generated by an &(autoreply)& transport.
14291 .option bounce_return_message main boolean true
14292 If this option is set false, none of the original message is included in
14293 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14294 &%bounce_return_body%&.
14297 .option bounce_return_size_limit main integer 100K
14298 .cindex "size" "of bounce, limit"
14299 .cindex "bounce message" "size limit"
14300 .cindex "limit" "bounce message size"
14301 This option sets a limit in bytes on the size of messages that are returned to
14302 senders as part of bounce messages when &%bounce_return_message%& is true. The
14303 limit should be less than the value of the global &%message_size_limit%& and of
14304 any &%message_size_limit%& settings on transports, to allow for the bounce text
14305 that Exim generates. If this option is set to zero there is no limit.
14307 When the body of any message that is to be included in a bounce message is
14308 greater than the limit, it is truncated, and a comment pointing this out is
14309 added at the top. The actual cutoff may be greater than the value given, owing
14310 to the use of buffering for transferring the message in chunks (typically 8K in
14311 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14314 .option bounce_sender_authentication main string unset
14315 .cindex "bounce message" "sender authentication"
14316 .cindex "authentication" "bounce message"
14317 .cindex "AUTH" "on bounce message"
14318 This option provides an authenticated sender address that is sent with any
14319 bounce messages generated by Exim that are sent over an authenticated SMTP
14320 connection. A typical setting might be:
14322 bounce_sender_authentication = mailer-daemon@my.domain.example
14324 which would cause bounce messages to be sent using the SMTP command:
14326 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14328 The value of &%bounce_sender_authentication%& must always be a complete email
14331 .option callout_domain_negative_expire main time 3h
14332 .cindex "caching" "callout timeouts"
14333 .cindex "callout" "caching timeouts"
14334 This option specifies the expiry time for negative callout cache data for a
14335 domain. See section &<<SECTcallver>>& for details of callout verification, and
14336 section &<<SECTcallvercache>>& for details of the caching.
14339 .option callout_domain_positive_expire main time 7d
14340 This option specifies the expiry time for positive callout cache data for a
14341 domain. See section &<<SECTcallver>>& for details of callout verification, and
14342 section &<<SECTcallvercache>>& for details of the caching.
14345 .option callout_negative_expire main time 2h
14346 This option specifies the expiry time for negative callout cache data for an
14347 address. See section &<<SECTcallver>>& for details of callout verification, and
14348 section &<<SECTcallvercache>>& for details of the caching.
14351 .option callout_positive_expire main time 24h
14352 This option specifies the expiry time for positive callout cache data for an
14353 address. See section &<<SECTcallver>>& for details of callout verification, and
14354 section &<<SECTcallvercache>>& for details of the caching.
14357 .option callout_random_local_part main string&!! "see below"
14358 This option defines the &"random"& local part that can be used as part of
14359 callout verification. The default value is
14361 $primary_hostname-$tod_epoch-testing
14363 See section &<<CALLaddparcall>>& for details of how this value is used.
14366 .option check_log_inodes main integer 100
14367 See &%check_spool_space%& below.
14370 .option check_log_space main integer 10M
14371 See &%check_spool_space%& below.
14373 .oindex "&%check_rfc2047_length%&"
14374 .cindex "RFC 2047" "disabling length check"
14375 .option check_rfc2047_length main boolean true
14376 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14377 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14378 word; strings to be encoded that exceed this length are supposed to use
14379 multiple encoded words. By default, Exim does not recognize encoded words that
14380 exceed the maximum length. However, it seems that some software, in violation
14381 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14382 set false, Exim recognizes encoded words of any length.
14385 .option check_spool_inodes main integer 100
14386 See &%check_spool_space%& below.
14389 .option check_spool_space main integer 10M
14390 .cindex "checking disk space"
14391 .cindex "disk space, checking"
14392 .cindex "spool directory" "checking space"
14393 The four &%check_...%& options allow for checking of disk resources before a
14394 message is accepted.
14396 .vindex "&$log_inodes$&"
14397 .vindex "&$log_space$&"
14398 .vindex "&$spool_inodes$&"
14399 .vindex "&$spool_space$&"
14400 When any of these options are nonzero, they apply to all incoming messages. If you
14401 want to apply different checks to different kinds of message, you can do so by
14402 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14403 &$spool_space$& in an ACL with appropriate additional conditions.
14406 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14407 either value is greater than zero, for example:
14409 check_spool_space = 100M
14410 check_spool_inodes = 100
14412 The spool partition is the one that contains the directory defined by
14413 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14416 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14417 files are written if either is greater than zero. These should be set only if
14418 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14420 If there is less space or fewer inodes than requested, Exim refuses to accept
14421 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14422 error response to the MAIL command. If ESMTP is in use and there was a
14423 SIZE parameter on the MAIL command, its value is added to the
14424 &%check_spool_space%& value, and the check is performed even if
14425 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14427 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14428 number of kilobytes (though specified in bytes).
14429 If a non-multiple of 1024 is specified, it is rounded up.
14431 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14432 failure a message is written to stderr and Exim exits with a non-zero code, as
14433 it obviously cannot send an error message of any kind.
14435 There is a slight performance penalty for these checks.
14436 Versions of Exim preceding 4.88 had these disabled by default;
14437 high-rate installations confident they will never run out of resources
14438 may wish to deliberately disable them.
14440 .option chunking_advertise_hosts main "host list&!!" *
14441 .cindex CHUNKING advertisement
14442 .cindex "RFC 3030" "CHUNKING"
14443 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
14445 Hosts may use the BDAT command as an alternate to DATA.
14447 .option debug_store main boolean &`false`&
14448 .cindex debugging "memory corruption"
14449 .cindex memory debugging
14450 This option, when true, enables extra checking in Exim's internal memory
14451 management. For use when a memory corruption issue is being investigated,
14452 it should normally be left as default.
14454 .option daemon_smtp_ports main string &`smtp`&
14455 .cindex "port" "for daemon"
14456 .cindex "TCP/IP" "setting listening ports"
14457 This option specifies one or more default SMTP ports on which the Exim daemon
14458 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14459 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14461 .option daemon_startup_retries main integer 9
14462 .cindex "daemon startup, retrying"
14463 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14464 the daemon at startup when it cannot immediately bind a listening socket
14465 (typically because the socket is already in use): &%daemon_startup_retries%&
14466 defines the number of retries after the first failure, and
14467 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14469 .option daemon_startup_sleep main time 30s
14470 See &%daemon_startup_retries%&.
14472 .option delay_warning main "time list" 24h
14473 .cindex "warning of delay"
14474 .cindex "delay warning, specifying"
14475 .cindex "queue" "delay warning"
14476 When a message is delayed, Exim sends a warning message to the sender at
14477 intervals specified by this option. The data is a colon-separated list of times
14478 after which to send warning messages. If the value of the option is an empty
14479 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14480 message has been on the queue for longer than the last time, the last interval
14481 between the times is used to compute subsequent warning times. For example,
14484 delay_warning = 4h:8h:24h
14486 the first message is sent after 4 hours, the second after 8 hours, and
14487 the third one after 24 hours. After that, messages are sent every 16 hours,
14488 because that is the interval between the last two times on the list. If you set
14489 just one time, it specifies the repeat interval. For example, with:
14493 messages are repeated every six hours. To stop warnings after a given time, set
14494 a very large time at the end of the list. For example:
14496 delay_warning = 2h:12h:99d
14498 Note that the option is only evaluated at the time a delivery attempt fails,
14499 which depends on retry and queue-runner configuration.
14500 Typically retries will be configured more frequently than warning messages.
14502 .option delay_warning_condition main string&!! "see below"
14503 .vindex "&$domain$&"
14504 The string is expanded at the time a warning message might be sent. If all the
14505 deferred addresses have the same domain, it is set in &$domain$& during the
14506 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14507 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14508 &"false"& (the comparison being done caselessly) then the warning message is
14509 not sent. The default is:
14511 delay_warning_condition = ${if or {\
14512 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14513 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14514 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14517 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14518 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14519 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14520 &"auto-replied"& in an &'Auto-Submitted:'& header.
14522 .option deliver_drop_privilege main boolean false
14523 .cindex "unprivileged delivery"
14524 .cindex "delivery" "unprivileged"
14525 If this option is set true, Exim drops its root privilege at the start of a
14526 delivery process, and runs as the Exim user throughout. This severely restricts
14527 the kinds of local delivery that are possible, but is viable in certain types
14528 of configuration. There is a discussion about the use of root privilege in
14529 chapter &<<CHAPsecurity>>&.
14531 .option deliver_queue_load_max main fixed-point unset
14532 .cindex "load average"
14533 .cindex "queue runner" "abandoning"
14534 When this option is set, a queue run is abandoned if the system load average
14535 becomes greater than the value of the option. The option has no effect on
14536 ancient operating systems on which Exim cannot determine the load average.
14537 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14540 .option delivery_date_remove main boolean true
14541 .cindex "&'Delivery-date:'& header line"
14542 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14543 message when it is delivered, in exactly the same way as &'Return-path:'& is
14544 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14545 should not be present in incoming messages, and this option causes them to be
14546 removed at the time the message is received, to avoid any problems that might
14547 occur when a delivered message is subsequently sent on to some other recipient.
14549 .option disable_fsync main boolean false
14550 .cindex "&[fsync()]&, disabling"
14551 This option is available only if Exim was built with the compile-time option
14552 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14553 a runtime configuration generates an &"unknown option"& error. You should not
14554 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14555 really, really, really understand what you are doing. &'No pre-compiled
14556 distributions of Exim should ever make this option available.'&
14558 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14559 updated files' data to be written to disc before continuing. Unexpected events
14560 such as crashes and power outages may cause data to be lost or scrambled.
14561 Here be Dragons. &*Beware.*&
14564 .option disable_ipv6 main boolean false
14565 .cindex "IPv6" "disabling"
14566 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14567 activities take place. AAAA records are never looked up, and any IPv6 addresses
14568 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14569 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14570 to handle IPv6 literal addresses.
14573 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14574 .cindex DKIM "controlling calls to the ACL"
14575 This option gives a list of DKIM domains for which the DKIM ACL is run.
14576 It is expanded after the message is received; by default it runs
14577 the ACL once for each signature in the message.
14578 See chapter &<<CHAPdkim>>&.
14581 .option dns_again_means_nonexist main "domain list&!!" unset
14582 .cindex "DNS" "&""try again""& response; overriding"
14583 DNS lookups give a &"try again"& response for the DNS errors
14584 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14585 keep trying to deliver a message, or to give repeated temporary errors to
14586 incoming mail. Sometimes the effect is caused by a badly set up name server and
14587 may persist for a long time. If a domain which exhibits this problem matches
14588 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14589 This option should be used with care. You can make it apply to reverse lookups
14590 by a setting such as this:
14592 dns_again_means_nonexist = *.in-addr.arpa
14594 This option applies to all DNS lookups that Exim does. It also applies when the
14595 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14596 since these are most likely to be caused by DNS lookup problems. The
14597 &(dnslookup)& router has some options of its own for controlling what happens
14598 when lookups for MX or SRV records give temporary errors. These more specific
14599 options are applied after this global option.
14601 .option dns_check_names_pattern main string "see below"
14602 .cindex "DNS" "pre-check of name syntax"
14603 When this option is set to a non-empty string, it causes Exim to check domain
14604 names for characters that are not allowed in host names before handing them to
14605 the DNS resolver, because some resolvers give temporary errors for names that
14606 contain unusual characters. If a domain name contains any unwanted characters,
14607 a &"not found"& result is forced, and the resolver is not called. The check is
14608 done by matching the domain name against a regular expression, which is the
14609 value of this option. The default pattern is
14611 dns_check_names_pattern = \
14612 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14614 which permits only letters, digits, slashes, and hyphens in components, but
14615 they must start and end with a letter or digit. Slashes are not, in fact,
14616 permitted in host names, but they are found in certain NS records (which can be
14617 accessed in Exim by using a &%dnsdb%& lookup). If you set
14618 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14621 .option dns_csa_search_limit main integer 5
14622 This option controls the depth of parental searching for CSA SRV records in the
14623 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14625 .option dns_csa_use_reverse main boolean true
14626 This option controls whether or not an IP address, given as a CSA domain, is
14627 reversed and looked up in the reverse DNS, as described in more detail in
14628 section &<<SECTverifyCSA>>&.
14631 .option dns_dnssec_ok main integer -1
14632 .cindex "DNS" "resolver options"
14633 .cindex "DNS" "DNSSEC"
14634 If this option is set to a non-negative number then Exim will initialise the
14635 DNS resolver library to either use or not use DNSSEC, overriding the system
14636 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14638 If the resolver library does not support DNSSEC then this option has no effect.
14641 .option dns_ipv4_lookup main "domain list&!!" unset
14642 .cindex "IPv6" "DNS lookup for AAAA records"
14643 .cindex "DNS" "IPv6 lookup for AAAA records"
14644 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14645 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14646 (A records) when trying to find IP addresses for hosts, unless the host's
14647 domain matches this list.
14649 This is a fudge to help with name servers that give big delays or otherwise do
14650 not work for the AAAA record type. In due course, when the world's name
14651 servers have all been upgraded, there should be no need for this option.
14654 .option dns_retrans main time 0s
14655 .cindex "DNS" "resolver options"
14656 .cindex timeout "dns lookup"
14657 .cindex "DNS" timeout
14658 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14659 retransmission and retry parameters for DNS lookups. Values of zero (the
14660 defaults) leave the system default settings unchanged. The first value is the
14661 time between retries, and the second is the number of retries. It isn't
14662 totally clear exactly how these settings affect the total time a DNS lookup may
14663 take. I haven't found any documentation about timeouts on DNS lookups; these
14664 parameter values are available in the external resolver interface structure,
14665 but nowhere does it seem to describe how they are used or what you might want
14667 See also the &%slow_lookup_log%& option.
14670 .option dns_retry main integer 0
14671 See &%dns_retrans%& above.
14674 .option dns_trust_aa main "domain list&!!" unset
14675 .cindex "DNS" "resolver options"
14676 .cindex "DNS" "DNSSEC"
14677 If this option is set then lookup results marked with the AA bit
14678 (Authoritative Answer) are trusted the same way as if they were
14679 DNSSEC-verified. The authority section's name of the answer must
14680 match with this expanded domain list.
14682 Use this option only if you talk directly to a resolver that is
14683 authoritative for some zones and does not set the AD (Authentic Data)
14684 bit in the answer. Some DNS servers may have an configuration option to
14685 mark the answers from their own zones as verified (they set the AD bit).
14686 Others do not have this option. It is considered as poor practice using
14687 a resolver that is an authoritative server for some zones.
14689 Use this option only if you really have to (e.g. if you want
14690 to use DANE for remote delivery to a server that is listed in the DNS
14691 zones that your resolver is authoritative for).
14693 If the DNS answer packet has the AA bit set and contains resource record
14694 in the answer section, the name of the first NS record appearing in the
14695 authority section is compared against the list. If the answer packet is
14696 authoritative but the answer section is empty, the name of the first SOA
14697 record in the authoritative section is used instead.
14699 .cindex "DNS" "resolver options"
14700 .option dns_use_edns0 main integer -1
14701 .cindex "DNS" "resolver options"
14702 .cindex "DNS" "EDNS0"
14703 .cindex "DNS" "OpenBSD
14704 If this option is set to a non-negative number then Exim will initialise the
14705 DNS resolver library to either use or not use EDNS0 extensions, overriding
14706 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14709 If the resolver library does not support EDNS0 then this option has no effect.
14711 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
14712 means that DNSSEC will not work with Exim on that platform either, unless Exim
14713 is linked against an alternative DNS client library.
14716 .option drop_cr main boolean false
14717 This is an obsolete option that is now a no-op. It used to affect the way Exim
14718 handled CR and LF characters in incoming messages. What happens now is
14719 described in section &<<SECTlineendings>>&.
14721 .option dsn_advertise_hosts main "host list&!!" unset
14722 .cindex "bounce messages" "success"
14723 .cindex "DSN" "success"
14724 .cindex "Delivery Status Notification" "success"
14725 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14726 and accepted from, these hosts.
14727 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14728 and RET and ORCPT options on MAIL FROM commands.
14729 A NOTIFY=SUCCESS option requests success-DSN messages.
14730 A NOTIFY= option with no argument requests that no delay or failure DSNs
14733 .option dsn_from main "string&!!" "see below"
14734 .cindex "&'From:'& header line" "in bounces"
14735 .cindex "bounce messages" "&'From:'& line, specifying"
14736 This option can be used to vary the contents of &'From:'& header lines in
14737 bounces and other automatically generated messages (&"Delivery Status
14738 Notifications"& &-- hence the name of the option). The default setting is:
14740 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14742 The value is expanded every time it is needed. If the expansion fails, a
14743 panic is logged, and the default value is used.
14745 .option envelope_to_remove main boolean true
14746 .cindex "&'Envelope-to:'& header line"
14747 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14748 message when it is delivered, in exactly the same way as &'Return-path:'& is
14749 handled. &'Envelope-to:'& records the original recipient address from the
14750 message's envelope that caused the delivery to happen. Such headers should not
14751 be present in incoming messages, and this option causes them to be removed at
14752 the time the message is received, to avoid any problems that might occur when a
14753 delivered message is subsequently sent on to some other recipient.
14756 .option errors_copy main "string list&!!" unset
14757 .cindex "bounce message" "copy to other address"
14758 .cindex "copy of bounce message"
14759 Setting this option causes Exim to send bcc copies of bounce messages that it
14760 generates to other addresses. &*Note*&: This does not apply to bounce messages
14761 coming from elsewhere. The value of the option is a colon-separated list of
14762 items. Each item consists of a pattern, terminated by white space, followed by
14763 a comma-separated list of email addresses. If a pattern contains spaces, it
14764 must be enclosed in double quotes.
14766 Each pattern is processed in the same way as a single item in an address list
14767 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14768 the bounce message, the message is copied to the addresses on the list. The
14769 items are scanned in order, and once a matching one is found, no further items
14770 are examined. For example:
14772 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14773 rqps@mydomain hostmaster@mydomain.example,\
14774 postmaster@mydomain.example
14776 .vindex "&$domain$&"
14777 .vindex "&$local_part$&"
14778 The address list is expanded before use. The expansion variables &$local_part$&
14779 and &$domain$& are set from the original recipient of the error message, and if
14780 there was any wildcard matching in the pattern, the expansion
14781 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14782 variables &$0$&, &$1$&, etc. are set in the normal way.
14785 .option errors_reply_to main string unset
14786 .cindex "bounce message" "&'Reply-to:'& in"
14787 By default, Exim's bounce and delivery warning messages contain the header line
14789 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14791 .oindex &%quota_warn_message%&
14792 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14793 A warning message that is generated by the &%quota_warn_message%& option in an
14794 &(appendfile)& transport may contain its own &'From:'& header line that
14795 overrides the default.
14797 Experience shows that people reply to bounce messages. If the
14798 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14799 and warning messages. For example:
14801 errors_reply_to = postmaster@my.domain.example
14803 The value of the option is not expanded. It must specify a valid RFC 2822
14804 address. However, if a warning message that is generated by the
14805 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14806 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14810 .option event_action main string&!! unset
14812 This option declares a string to be expanded for Exim's events mechanism.
14813 For details see chapter &<<CHAPevents>>&.
14816 .option exim_group main string "compile-time configured"
14817 .cindex "gid (group id)" "Exim's own"
14818 .cindex "Exim group"
14819 This option changes the gid under which Exim runs when it gives up root
14820 privilege. The default value is compiled into the binary. The value of this
14821 option is used only when &%exim_user%& is also set. Unless it consists entirely
14822 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14823 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
14827 .option exim_path main string "see below"
14828 .cindex "Exim binary, path name"
14829 This option specifies the path name of the Exim binary, which is used when Exim
14830 needs to re-exec itself. The default is set up to point to the file &'exim'& in
14831 the directory configured at compile time by the BIN_DIRECTORY setting. It
14832 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
14834 &*Warning*&: Do not use a macro to define the value of this option, because
14835 you will break those Exim utilities that scan the configuration file to find
14836 where the binary is. (They then use the &%-bP%& option to extract option
14837 settings such as the value of &%spool_directory%&.)
14840 .option exim_user main string "compile-time configured"
14841 .cindex "uid (user id)" "Exim's own"
14842 .cindex "Exim user"
14843 This option changes the uid under which Exim runs when it gives up root
14844 privilege. The default value is compiled into the binary. Ownership of the run
14845 time configuration file and the use of the &%-C%& and &%-D%& command line
14846 options is checked against the values in the binary, not what is set here.
14848 Unless it consists entirely of digits, the string is looked up using
14849 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
14850 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
14851 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
14854 .option extra_local_interfaces main "string list" unset
14855 This option defines network interfaces that are to be considered local when
14856 routing, but which are not used for listening by the daemon. See section
14857 &<<SECTreclocipadd>>& for details.
14860 . Allow this long option name to split; give it unsplit as a fifth argument
14861 . for the automatic .oindex that is generated by .option.
14863 .option "extract_addresses_remove_arguments" main boolean true &&&
14864 extract_addresses_remove_arguments
14866 .cindex "command line" "addresses with &%-t%&"
14867 .cindex "Sendmail compatibility" "&%-t%& option"
14868 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
14869 are present on the command line when the &%-t%& option is used to build an
14870 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
14871 line addresses are removed from the recipients list. This is also how Smail
14872 behaves. However, other Sendmail documentation (the O'Reilly book) states that
14873 command line addresses are added to those obtained from the header lines. When
14874 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
14875 argument headers. If it is set false, Exim adds rather than removes argument
14879 .option finduser_retries main integer 0
14880 .cindex "NIS, retrying user lookups"
14881 On systems running NIS or other schemes in which user and group information is
14882 distributed from a remote system, there can be times when &[getpwnam()]& and
14883 related functions fail, even when given valid data, because things time out.
14884 Unfortunately these failures cannot be distinguished from genuine &"not found"&
14885 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
14886 many extra times to find a user or a group, waiting for one second between
14889 .cindex "&_/etc/passwd_&" "multiple reading of"
14890 You should not set this option greater than zero if your user information is in
14891 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
14892 search the file multiple times for non-existent users, and also cause delay.
14896 .option freeze_tell main "string list, comma separated" unset
14897 .cindex "freezing messages" "sending a message when freezing"
14898 On encountering certain errors, or when configured to do so in a system filter,
14899 ACL, or special router, Exim freezes a message. This means that no further
14900 delivery attempts take place until an administrator thaws the message, or the
14901 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
14902 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
14903 warning message whenever it freezes something, unless the message it is
14904 freezing is a locally-generated bounce message. (Without this exception there
14905 is the possibility of looping.) The warning message is sent to the addresses
14906 supplied as the comma-separated value of this option. If several of the
14907 message's addresses cause freezing, only a single message is sent. If the
14908 freezing was automatic, the reason(s) for freezing can be found in the message
14909 log. If you configure freezing in a filter or ACL, you must arrange for any
14910 logging that you require.
14913 .option gecos_name main string&!! unset
14915 .cindex "&""gecos""& field, parsing"
14916 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
14917 password file to hold other information in addition to users' real names. Exim
14918 looks up this field for use when it is creating &'Sender:'& or &'From:'&
14919 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
14920 of the field are used unchanged, except that, if an ampersand is encountered,
14921 it is replaced by the user's login name with the first character forced to
14922 upper case, since this is a convention that is observed on many systems.
14924 When these options are set, &%gecos_pattern%& is treated as a regular
14925 expression that is to be applied to the field (again with && replaced by the
14926 login name), and if it matches, &%gecos_name%& is expanded and used as the
14929 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
14930 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
14931 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
14932 name terminates at the first comma, the following can be used:
14934 gecos_pattern = ([^,]*)
14938 .option gecos_pattern main string unset
14939 See &%gecos_name%& above.
14942 .option gnutls_compat_mode main boolean unset
14943 This option controls whether GnuTLS is used in compatibility mode in an Exim
14944 server. This reduces security slightly, but improves interworking with older
14945 implementations of TLS.
14948 option gnutls_allow_auto_pkcs11 main boolean unset
14949 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
14950 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
14953 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
14958 .option headers_charset main string "see below"
14959 This option sets a default character set for translating from encoded MIME
14960 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
14961 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
14962 ultimate default is ISO-8859-1. For more details see the description of header
14963 insertions in section &<<SECTexpansionitems>>&.
14967 .option header_maxsize main integer "see below"
14968 .cindex "header section" "maximum size of"
14969 .cindex "limit" "size of message header section"
14970 This option controls the overall maximum size of a message's header
14971 section. The default is the value of HEADER_MAXSIZE in
14972 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
14973 sections are rejected.
14976 .option header_line_maxsize main integer 0
14977 .cindex "header lines" "maximum size of"
14978 .cindex "limit" "size of one header line"
14979 This option limits the length of any individual header line in a message, after
14980 all the continuations have been joined together. Messages with individual
14981 header lines that are longer than the limit are rejected. The default value of
14982 zero means &"no limit"&.
14987 .option helo_accept_junk_hosts main "host list&!!" unset
14988 .cindex "HELO" "accepting junk data"
14989 .cindex "EHLO" "accepting junk data"
14990 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
14991 mail, and gives an error response for invalid data. Unfortunately, there are
14992 some SMTP clients that send syntactic junk. They can be accommodated by setting
14993 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
14994 if you want to do semantic checking.
14995 See also &%helo_allow_chars%& for a way of extending the permitted character
14999 .option helo_allow_chars main string unset
15000 .cindex "HELO" "underscores in"
15001 .cindex "EHLO" "underscores in"
15002 .cindex "underscore in EHLO/HELO"
15003 This option can be set to a string of rogue characters that are permitted in
15004 all EHLO and HELO names in addition to the standard letters, digits,
15005 hyphens, and dots. If you really must allow underscores, you can set
15007 helo_allow_chars = _
15009 Note that the value is one string, not a list.
15012 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
15013 .cindex "HELO" "forcing reverse lookup"
15014 .cindex "EHLO" "forcing reverse lookup"
15015 If the domain given by a client in a HELO or EHLO command matches this
15016 list, a reverse lookup is done in order to establish the host's true name. The
15017 default forces a lookup if the client host gives the server's name or any of
15018 its IP addresses (in brackets), something that broken clients have been seen to
15022 .option helo_try_verify_hosts main "host list&!!" unset
15023 .cindex "HELO verifying" "optional"
15024 .cindex "EHLO" "verifying, optional"
15025 By default, Exim just checks the syntax of HELO and EHLO commands (see
15026 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
15027 to do more extensive checking of the data supplied by these commands. The ACL
15028 condition &`verify = helo`& is provided to make this possible.
15029 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
15030 to force the check to occur. From release 4.53 onwards, this is no longer
15031 necessary. If the check has not been done before &`verify = helo`& is
15032 encountered, it is done at that time. Consequently, this option is obsolete.
15033 Its specification is retained here for backwards compatibility.
15035 When an EHLO or HELO command is received, if the calling host matches
15036 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
15037 EHLO command either:
15040 is an IP literal matching the calling address of the host, or
15042 .cindex "DNS" "reverse lookup"
15043 .cindex "reverse DNS lookup"
15044 matches the host name that Exim obtains by doing a reverse lookup of the
15045 calling host address, or
15047 when looked up in DNS yields the calling host address.
15050 However, the EHLO or HELO command is not rejected if any of the checks
15051 fail. Processing continues, but the result of the check is remembered, and can
15052 be detected later in an ACL by the &`verify = helo`& condition.
15054 If DNS was used for successful verification, the variable
15055 .cindex "DNS" "DNSSEC"
15056 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
15058 .option helo_verify_hosts main "host list&!!" unset
15059 .cindex "HELO verifying" "mandatory"
15060 .cindex "EHLO" "verifying, mandatory"
15061 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
15062 backwards compatibility. For hosts that match this option, Exim checks the host
15063 name given in the HELO or EHLO in the same way as for
15064 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
15065 rejected with a 550 error, and entries are written to the main and reject logs.
15066 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
15069 .option hold_domains main "domain list&!!" unset
15070 .cindex "domain" "delaying delivery"
15071 .cindex "delivery" "delaying certain domains"
15072 This option allows mail for particular domains to be held on the queue
15073 manually. The option is overridden if a message delivery is forced with the
15074 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
15075 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
15076 item in &%hold_domains%&, no routing or delivery for that address is done, and
15077 it is deferred every time the message is looked at.
15079 This option is intended as a temporary operational measure for delaying the
15080 delivery of mail while some problem is being sorted out, or some new
15081 configuration tested. If you just want to delay the processing of some
15082 domains until a queue run occurs, you should use &%queue_domains%& or
15083 &%queue_smtp_domains%&, not &%hold_domains%&.
15085 A setting of &%hold_domains%& does not override Exim's code for removing
15086 messages from the queue if they have been there longer than the longest retry
15087 time in any retry rule. If you want to hold messages for longer than the normal
15088 retry times, insert a dummy retry rule with a long retry time.
15091 .option host_lookup main "host list&!!" unset
15092 .cindex "host name" "lookup, forcing"
15093 Exim does not look up the name of a calling host from its IP address unless it
15094 is required to compare against some host list, or the host matches
15095 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
15096 option (which normally contains IP addresses rather than host names). The
15097 default configuration file contains
15101 which causes a lookup to happen for all hosts. If the expense of these lookups
15102 is felt to be too great, the setting can be changed or removed.
15104 After a successful reverse lookup, Exim does a forward lookup on the name it
15105 has obtained, to verify that it yields the IP address that it started with. If
15106 this check fails, Exim behaves as if the name lookup failed.
15108 .vindex "&$host_lookup_failed$&"
15109 .vindex "&$sender_host_name$&"
15110 After any kind of failure, the host name (in &$sender_host_name$&) remains
15111 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
15112 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
15113 &`verify = reverse_host_lookup`& in ACLs.
15116 .option host_lookup_order main "string list" &`bydns:byaddr`&
15117 This option specifies the order of different lookup methods when Exim is trying
15118 to find a host name from an IP address. The default is to do a DNS lookup
15119 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
15120 if that fails. You can change the order of these lookups, or omit one entirely,
15123 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
15124 multiple PTR records in the DNS and the IP address is not listed in
15125 &_/etc/hosts_&. Different operating systems give different results in this
15126 case. That is why the default tries a DNS lookup first.
15130 .option host_reject_connection main "host list&!!" unset
15131 .cindex "host" "rejecting connections from"
15132 If this option is set, incoming SMTP calls from the hosts listed are rejected
15133 as soon as the connection is made.
15134 This option is obsolete, and retained only for backward compatibility, because
15135 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
15136 connections immediately.
15138 The ability to give an immediate rejection (either by this option or using an
15139 ACL) is provided for use in unusual cases. Many hosts will just try again,
15140 sometimes without much delay. Normally, it is better to use an ACL to reject
15141 incoming messages at a later stage, such as after RCPT commands. See
15142 chapter &<<CHAPACL>>&.
15145 .option hosts_connection_nolog main "host list&!!" unset
15146 .cindex "host" "not logging connections from"
15147 This option defines a list of hosts for which connection logging does not
15148 happen, even though the &%smtp_connection%& log selector is set. For example,
15149 you might want not to log SMTP connections from local processes, or from
15150 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
15151 the daemon; you should therefore strive to restrict its value to a short inline
15152 list of IP addresses and networks. To disable logging SMTP connections from
15153 local processes, you must create a host list with an empty item. For example:
15155 hosts_connection_nolog = :
15157 If the &%smtp_connection%& log selector is not set, this option has no effect.
15161 .option hosts_proxy main "host list&!!" unset
15162 .cindex proxy "proxy protocol"
15163 This option enables use of Proxy Protocol proxies for incoming
15164 connections. For details see section &<<SECTproxyInbound>>&.
15167 .option hosts_treat_as_local main "domain list&!!" unset
15168 .cindex "local host" "domains treated as"
15169 .cindex "host" "treated as local"
15170 If this option is set, any host names that match the domain list are treated as
15171 if they were the local host when Exim is scanning host lists obtained from MX
15173 or other sources. Note that the value of this option is a domain list, not a
15174 host list, because it is always used to check host names, not IP addresses.
15176 This option also applies when Exim is matching the special items
15177 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15178 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15179 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15180 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15181 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15182 interfaces and recognizing the local host.
15185 .option ibase_servers main "string list" unset
15186 .cindex "InterBase" "server list"
15187 This option provides a list of InterBase servers and associated connection data,
15188 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15189 The option is available only if Exim has been built with InterBase support.
15193 .option ignore_bounce_errors_after main time 10w
15194 .cindex "bounce message" "discarding"
15195 .cindex "discarding bounce message"
15196 This option affects the processing of bounce messages that cannot be delivered,
15197 that is, those that suffer a permanent delivery failure. (Bounce messages that
15198 suffer temporary delivery failures are of course retried in the usual way.)
15200 After a permanent delivery failure, bounce messages are frozen,
15201 because there is no sender to whom they can be returned. When a frozen bounce
15202 message has been on the queue for more than the given time, it is unfrozen at
15203 the next queue run, and a further delivery is attempted. If delivery fails
15204 again, the bounce message is discarded. This makes it possible to keep failed
15205 bounce messages around for a shorter time than the normal maximum retry time
15206 for frozen messages. For example,
15208 ignore_bounce_errors_after = 12h
15210 retries failed bounce message deliveries after 12 hours, discarding any further
15211 failures. If the value of this option is set to a zero time period, bounce
15212 failures are discarded immediately. Setting a very long time (as in the default
15213 value) has the effect of disabling this option. For ways of automatically
15214 dealing with other kinds of frozen message, see &%auto_thaw%& and
15215 &%timeout_frozen_after%&.
15218 .option ignore_fromline_hosts main "host list&!!" unset
15219 .cindex "&""From""& line"
15220 .cindex "UUCP" "&""From""& line"
15221 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15222 the headers of a message. By default this is treated as the start of the
15223 message's body, which means that any following headers are not recognized as
15224 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15225 match those hosts that insist on sending it. If the sender is actually a local
15226 process rather than a remote host, and is using &%-bs%& to inject the messages,
15227 &%ignore_fromline_local%& must be set to achieve this effect.
15230 .option ignore_fromline_local main boolean false
15231 See &%ignore_fromline_hosts%& above.
15233 .option keep_environment main "string list" unset
15234 .cindex "environment" "values from"
15235 This option contains a string list of environment variables to keep.
15236 You have to trust these variables or you have to be sure that
15237 these variables do not impose any security risk. Keep in mind that
15238 during the startup phase Exim is running with an effective UID 0 in most
15239 installations. As the default value is an empty list, the default
15240 environment for using libraries, running embedded Perl code, or running
15241 external binaries is empty, and does not not even contain PATH or HOME.
15243 Actually the list is interpreted as a list of patterns
15244 (&<<SECTlistexpand>>&), except that it is not expanded first.
15246 WARNING: Macro substitution is still done first, so having a macro
15247 FOO and having FOO_HOME in your &%keep_environment%& option may have
15248 unexpected results. You may work around this using a regular expression
15249 that does not match the macro name: ^[F]OO_HOME$.
15251 Current versions of Exim issue a warning during startup if you do not mention
15252 &%keep_environment%& in your runtime configuration file and if your
15253 current environment is not empty. Future versions may not issue that warning
15256 See the &%add_environment%& main config option for a way to set
15257 environment variables to a fixed value. The environment for &(pipe)&
15258 transports is handled separately, see section &<<SECTpipeenv>>& for
15262 .option keep_malformed main time 4d
15263 This option specifies the length of time to keep messages whose spool files
15264 have been corrupted in some way. This should, of course, never happen. At the
15265 next attempt to deliver such a message, it gets removed. The incident is
15269 .option ldap_ca_cert_dir main string unset
15270 .cindex "LDAP", "TLS CA certificate directory"
15271 .cindex certificate "directory for LDAP"
15272 This option indicates which directory contains CA certificates for verifying
15273 a TLS certificate presented by an LDAP server.
15274 While Exim does not provide a default value, your SSL library may.
15275 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15276 and constrained to be a directory.
15279 .option ldap_ca_cert_file main string unset
15280 .cindex "LDAP", "TLS CA certificate file"
15281 .cindex certificate "file for LDAP"
15282 This option indicates which file contains CA certificates for verifying
15283 a TLS certificate presented by an LDAP server.
15284 While Exim does not provide a default value, your SSL library may.
15285 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15286 and constrained to be a file.
15289 .option ldap_cert_file main string unset
15290 .cindex "LDAP" "TLS client certificate file"
15291 .cindex certificate "file for LDAP"
15292 This option indicates which file contains an TLS client certificate which
15293 Exim should present to the LDAP server during TLS negotiation.
15294 Should be used together with &%ldap_cert_key%&.
15297 .option ldap_cert_key main string unset
15298 .cindex "LDAP" "TLS client key file"
15299 .cindex certificate "key for LDAP"
15300 This option indicates which file contains the secret/private key to use
15301 to prove identity to the LDAP server during TLS negotiation.
15302 Should be used together with &%ldap_cert_file%&, which contains the
15303 identity to be proven.
15306 .option ldap_cipher_suite main string unset
15307 .cindex "LDAP" "TLS cipher suite"
15308 This controls the TLS cipher-suite negotiation during TLS negotiation with
15309 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15310 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15313 .option ldap_default_servers main "string list" unset
15314 .cindex "LDAP" "default servers"
15315 This option provides a list of LDAP servers which are tried in turn when an
15316 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15317 details of LDAP queries. This option is available only when Exim has been built
15321 .option ldap_require_cert main string unset.
15322 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15323 This should be one of the values "hard", "demand", "allow", "try" or "never".
15324 A value other than one of these is interpreted as "never".
15325 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15326 Although Exim does not set a default, the LDAP library probably defaults
15330 .option ldap_start_tls main boolean false
15331 .cindex "LDAP" "whether or not to negotiate TLS"
15332 If set, Exim will attempt to negotiate TLS with the LDAP server when
15333 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15334 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15336 In the event of failure to negotiate TLS, the action taken is controlled
15337 by &%ldap_require_cert%&.
15338 This option is ignored for &`ldapi`& connections.
15341 .option ldap_version main integer unset
15342 .cindex "LDAP" "protocol version, forcing"
15343 This option can be used to force Exim to set a specific protocol version for
15344 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15345 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15346 the LDAP headers; otherwise it is 2. This option is available only when Exim
15347 has been built with LDAP support.
15351 .option local_from_check main boolean true
15352 .cindex "&'Sender:'& header line" "disabling addition of"
15353 .cindex "&'From:'& header line" "disabling checking of"
15354 When a message is submitted locally (that is, not over a TCP/IP connection) by
15355 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15356 checks that the &'From:'& header line matches the login of the calling user and
15357 the domain specified by &%qualify_domain%&.
15359 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15360 locally submitted message is automatically qualified by Exim, unless the
15361 &%-bnq%& command line option is used.
15363 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15364 on the local part. If the &'From:'& header line does not match, Exim adds a
15365 &'Sender:'& header with an address constructed from the calling user's login
15366 and the default qualify domain.
15368 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15369 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15370 &'Sender:'& header lines supplied by untrusted users, you must also set
15371 &%local_sender_retain%& to be true.
15373 .cindex "envelope sender"
15374 These options affect only the header lines in the message. The envelope sender
15375 is still forced to be the login id at the qualify domain unless
15376 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15378 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15379 request similar header line checking. See section &<<SECTthesenhea>>&, which
15380 has more details about &'Sender:'& processing.
15385 .option local_from_prefix main string unset
15386 When Exim checks the &'From:'& header line of locally submitted messages for
15387 matching the login id (see &%local_from_check%& above), it can be configured to
15388 ignore certain prefixes and suffixes in the local part of the address. This is
15389 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15390 appropriate lists, in the same form as the &%local_part_prefix%& and
15391 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15394 local_from_prefix = *-
15396 is set, a &'From:'& line containing
15398 From: anything-user@your.domain.example
15400 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15401 matches the actual sender address that is constructed from the login name and
15405 .option local_from_suffix main string unset
15406 See &%local_from_prefix%& above.
15409 .option local_interfaces main "string list" "see below"
15410 This option controls which network interfaces are used by the daemon for
15411 listening; they are also used to identify the local host when routing. Chapter
15412 &<<CHAPinterfaces>>& contains a full description of this option and the related
15413 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15414 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15415 &%local_interfaces%& is
15417 local_interfaces = 0.0.0.0
15419 when Exim is built without IPv6 support; otherwise it is
15421 local_interfaces = <; ::0 ; 0.0.0.0
15424 .option local_scan_timeout main time 5m
15425 .cindex "timeout" "for &[local_scan()]& function"
15426 .cindex "&[local_scan()]& function" "timeout"
15427 This timeout applies to the &[local_scan()]& function (see chapter
15428 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15429 the incoming message is rejected with a temporary error if it is an SMTP
15430 message. For a non-SMTP message, the message is dropped and Exim ends with a
15431 non-zero code. The incident is logged on the main and reject logs.
15435 .option local_sender_retain main boolean false
15436 .cindex "&'Sender:'& header line" "retaining from local submission"
15437 When a message is submitted locally (that is, not over a TCP/IP connection) by
15438 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15439 do not want this to happen, you must set &%local_sender_retain%&, and you must
15440 also set &%local_from_check%& to be false (Exim will complain if you do not).
15441 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15442 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15447 .option localhost_number main string&!! unset
15448 .cindex "host" "locally unique number for"
15449 .cindex "message ids" "with multiple hosts"
15450 .vindex "&$localhost_number$&"
15451 Exim's message ids are normally unique only within the local host. If
15452 uniqueness among a set of hosts is required, each host must set a different
15453 value for the &%localhost_number%& option. The string is expanded immediately
15454 after reading the configuration file (so that a number can be computed from the
15455 host name, for example) and the result of the expansion must be a number in the
15456 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15457 systems). This is available in subsequent string expansions via the variable
15458 &$localhost_number$&. When &%localhost_number is set%&, the final two
15459 characters of the message id, instead of just being a fractional part of the
15460 time, are computed from the time and the local host number as described in
15461 section &<<SECTmessiden>>&.
15465 .option log_file_path main "string list&!!" "set at compile time"
15466 .cindex "log" "file path for"
15467 This option sets the path which is used to determine the names of Exim's log
15468 files, or indicates that logging is to be to syslog, or both. It is expanded
15469 when Exim is entered, so it can, for example, contain a reference to the host
15470 name. If no specific path is set for the log files at compile or run time,
15471 or if the option is unset at run time (i.e. &`log_file_path = `&)
15472 they are written in a sub-directory called &_log_& in Exim's spool directory.
15473 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15474 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15475 used. If this string is fixed at your installation (contains no expansion
15476 variables) it is recommended that you do not set this option in the
15477 configuration file, but instead supply the path using LOG_FILE_PATH in
15478 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15479 early on &-- in particular, failure to read the configuration file.
15482 .option log_selector main string unset
15483 .cindex "log" "selectors"
15484 This option can be used to reduce or increase the number of things that Exim
15485 writes to its log files. Its argument is made up of names preceded by plus or
15486 minus characters. For example:
15488 log_selector = +arguments -retry_defer
15490 A list of possible names and what they control is given in the chapter on
15491 logging, in section &<<SECTlogselector>>&.
15494 .option log_timezone main boolean false
15495 .cindex "log" "timezone for entries"
15496 .vindex "&$tod_log$&"
15497 .vindex "&$tod_zone$&"
15498 By default, the timestamps on log lines are in local time without the
15499 timezone. This means that if your timezone changes twice a year, the timestamps
15500 in log lines are ambiguous for an hour when the clocks go back. One way of
15501 avoiding this problem is to set the timezone to UTC. An alternative is to set
15502 &%log_timezone%& true. This turns on the addition of the timezone offset to
15503 timestamps in log lines. Turning on this option can add quite a lot to the size
15504 of log files because each line is extended by 6 characters. Note that the
15505 &$tod_log$& variable contains the log timestamp without the zone, but there is
15506 another variable called &$tod_zone$& that contains just the timezone offset.
15509 .option lookup_open_max main integer 25
15510 .cindex "too many open files"
15511 .cindex "open files, too many"
15512 .cindex "file" "too many open"
15513 .cindex "lookup" "maximum open files"
15514 .cindex "limit" "open files for lookups"
15515 This option limits the number of simultaneously open files for single-key
15516 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15517 Exim normally keeps these files open during routing, because often the same
15518 file is required several times. If the limit is reached, Exim closes the least
15519 recently used file. Note that if you are using the &'ndbm'& library, it
15520 actually opens two files for each logical DBM database, though it still counts
15521 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15522 open files"& errors with NDBM, you need to reduce the value of
15523 &%lookup_open_max%&.
15526 .option max_username_length main integer 0
15527 .cindex "length of login name"
15528 .cindex "user name" "maximum length"
15529 .cindex "limit" "user name length"
15530 Some operating systems are broken in that they truncate long arguments to
15531 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15532 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15533 an argument that is longer behaves as if &[getpwnam()]& failed.
15536 .option message_body_newlines main bool false
15537 .cindex "message body" "newlines in variables"
15538 .cindex "newline" "in message body variables"
15539 .vindex "&$message_body$&"
15540 .vindex "&$message_body_end$&"
15541 By default, newlines in the message body are replaced by spaces when setting
15542 the &$message_body$& and &$message_body_end$& expansion variables. If this
15543 option is set true, this no longer happens.
15546 .option message_body_visible main integer 500
15547 .cindex "body of message" "visible size"
15548 .cindex "message body" "visible size"
15549 .vindex "&$message_body$&"
15550 .vindex "&$message_body_end$&"
15551 This option specifies how much of a message's body is to be included in the
15552 &$message_body$& and &$message_body_end$& expansion variables.
15555 .option message_id_header_domain main string&!! unset
15556 .cindex "&'Message-ID:'& header line"
15557 If this option is set, the string is expanded and used as the right hand side
15558 (domain) of the &'Message-ID:'& header that Exim creates if a
15559 locally-originated incoming message does not have one. &"Locally-originated"&
15560 means &"not received over TCP/IP."&
15561 Otherwise, the primary host name is used.
15562 Only letters, digits, dot and hyphen are accepted; any other characters are
15563 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15564 empty string, the option is ignored.
15567 .option message_id_header_text main string&!! unset
15568 If this variable is set, the string is expanded and used to augment the text of
15569 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15570 message does not have one. The text of this header is required by RFC 2822 to
15571 take the form of an address. By default, Exim uses its internal message id as
15572 the local part, and the primary host name as the domain. If this option is set,
15573 it is expanded, and provided the expansion is not forced to fail, and does not
15574 yield an empty string, the result is inserted into the header immediately
15575 before the @, separated from the internal message id by a dot. Any characters
15576 that are illegal in an address are automatically converted into hyphens. This
15577 means that variables such as &$tod_log$& can be used, because the spaces and
15578 colons will become hyphens.
15581 .option message_logs main boolean true
15582 .cindex "message logs" "disabling"
15583 .cindex "log" "message log; disabling"
15584 If this option is turned off, per-message log files are not created in the
15585 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15586 Exim, by reducing the number of files involved in handling a message from a
15587 minimum of four (header spool file, body spool file, delivery journal, and
15588 per-message log) to three. The other major I/O activity is Exim's main log,
15589 which is not affected by this option.
15592 .option message_size_limit main string&!! 50M
15593 .cindex "message" "size limit"
15594 .cindex "limit" "message size"
15595 .cindex "size" "of message, limit"
15596 This option limits the maximum size of message that Exim will process. The
15597 value is expanded for each incoming connection so, for example, it can be made
15598 to depend on the IP address of the remote host for messages arriving via
15599 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15600 optionally followed by K or M.
15602 &*Note*&: This limit cannot be made to depend on a message's sender or any
15603 other properties of an individual message, because it has to be advertised in
15604 the server's response to EHLO. String expansion failure causes a temporary
15605 error. A value of zero means no limit, but its use is not recommended. See also
15606 &%bounce_return_size_limit%&.
15608 Incoming SMTP messages are failed with a 552 error if the limit is
15609 exceeded; locally-generated messages either get a stderr message or a delivery
15610 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15611 an oversized message is logged in both the main and the reject logs. See also
15612 the generic transport option &%message_size_limit%&, which limits the size of
15613 message that an individual transport can process.
15615 If you use a virus-scanner and set this option to to a value larger than the
15616 maximum size that your virus-scanner is configured to support, you may get
15617 failures triggered by large mails. The right size to configure for the
15618 virus-scanner depends upon what data is passed and the options in use but it's
15619 probably safest to just set it to a little larger than this value. E.g., with a
15620 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15621 some problems may result.
15623 A value of 0 will disable size limit checking; Exim will still advertise the
15624 SIZE extension in an EHLO response, but without a limit, so as to permit
15625 SMTP clients to still indicate the message size along with the MAIL verb.
15628 .option move_frozen_messages main boolean false
15629 .cindex "frozen messages" "moving"
15630 This option, which is available only if Exim has been built with the setting
15632 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15634 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15635 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15636 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15637 standard utilities for handling such moved messages, and they do not show up in
15638 lists generated by &%-bp%& or by the Exim monitor.
15641 .option mua_wrapper main boolean false
15642 Setting this option true causes Exim to run in a very restrictive mode in which
15643 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15644 contains a full description of this facility.
15648 .option mysql_servers main "string list" unset
15649 .cindex "MySQL" "server list"
15650 This option provides a list of MySQL servers and associated connection data, to
15651 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15652 option is available only if Exim has been built with MySQL support.
15655 .option never_users main "string list&!!" unset
15656 This option is expanded just once, at the start of Exim's processing. Local
15657 message deliveries are normally run in processes that are setuid to the
15658 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15659 It is usually desirable to prevent any deliveries from running as root, as a
15662 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15663 list of users that must not be used for local deliveries. This list is fixed in
15664 the binary and cannot be overridden by the configuration file. By default, it
15665 contains just the single user name &"root"&. The &%never_users%& runtime option
15666 can be used to add more users to the fixed list.
15668 If a message is to be delivered as one of the users on the fixed list or the
15669 &%never_users%& list, an error occurs, and delivery is deferred. A common
15672 never_users = root:daemon:bin
15674 Including root is redundant if it is also on the fixed list, but it does no
15675 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15679 .option openssl_options main "string list" "+no_sslv2 +single_dh_use"
15680 .cindex "OpenSSL "compatibility options"
15681 This option allows an administrator to adjust the SSL options applied
15682 by OpenSSL to connections. It is given as a space-separated list of items,
15683 each one to be +added or -subtracted from the current value.
15685 This option is only available if Exim is built against OpenSSL. The values
15686 available for this option vary according to the age of your OpenSSL install.
15687 The &"all"& value controls a subset of flags which are available, typically
15688 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15689 list the values known on your system and Exim should support all the
15690 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15691 names lose the leading &"SSL_OP_"& and are lower-cased.
15693 Note that adjusting the options can have severe impact upon the security of
15694 SSL as used by Exim. It is possible to disable safety checks and shoot
15695 yourself in the foot in various unpleasant ways. This option should not be
15696 adjusted lightly. An unrecognised item will be detected at startup, by
15697 invoking Exim with the &%-bV%& flag.
15699 The option affects Exim operating both as a server and as a client.
15701 Historical note: prior to release 4.80, Exim defaulted this value to
15702 "+dont_insert_empty_fragments", which may still be needed for compatibility
15703 with some clients, but which lowers security by increasing exposure to
15704 some now infamous attacks.
15708 # Make both old MS and old Eudora happy:
15709 openssl_options = -all +microsoft_big_sslv3_buffer \
15710 +dont_insert_empty_fragments
15712 # Disable older protocol versions:
15713 openssl_options = +no_sslv2 +no_sslv3
15716 Possible options may include:
15720 &`allow_unsafe_legacy_renegotiation`&
15722 &`cipher_server_preference`&
15724 &`dont_insert_empty_fragments`&
15728 &`legacy_server_connect`&
15730 &`microsoft_big_sslv3_buffer`&
15732 &`microsoft_sess_id_bug`&
15734 &`msie_sslv2_rsa_padding`&
15736 &`netscape_challenge_bug`&
15738 &`netscape_reuse_cipher_change_bug`&
15742 &`no_session_resumption_on_renegotiation`&
15756 &`safari_ecdhe_ecdsa_bug`&
15760 &`single_ecdh_use`&
15762 &`ssleay_080_client_dh_bug`&
15764 &`sslref2_reuse_cert_type_bug`&
15766 &`tls_block_padding_bug`&
15770 &`tls_rollback_bug`&
15773 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15774 all clients connecting using the MacOS SecureTransport TLS facility prior
15775 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15776 to negotiate TLS then this option value might help, provided that your OpenSSL
15777 release is new enough to contain this work-around. This may be a situation
15778 where you have to upgrade OpenSSL to get buggy clients working.
15781 .option oracle_servers main "string list" unset
15782 .cindex "Oracle" "server list"
15783 This option provides a list of Oracle servers and associated connection data,
15784 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15785 The option is available only if Exim has been built with Oracle support.
15788 .option percent_hack_domains main "domain list&!!" unset
15789 .cindex "&""percent hack""&"
15790 .cindex "source routing" "in email address"
15791 .cindex "address" "source-routed"
15792 The &"percent hack"& is the convention whereby a local part containing a
15793 percent sign is re-interpreted as a new email address, with the percent
15794 replaced by @. This is sometimes called &"source routing"&, though that term is
15795 also applied to RFC 2822 addresses that begin with an @ character. If this
15796 option is set, Exim implements the percent facility for those domains listed,
15797 but no others. This happens before an incoming SMTP address is tested against
15800 &*Warning*&: The &"percent hack"& has often been abused by people who are
15801 trying to get round relaying restrictions. For this reason, it is best avoided
15802 if at all possible. Unfortunately, a number of less security-conscious MTAs
15803 implement it unconditionally. If you are running Exim on a gateway host, and
15804 routing mail through to internal MTAs without processing the local parts, it is
15805 a good idea to reject recipient addresses with percent characters in their
15806 local parts. Exim's default configuration does this.
15809 .option perl_at_start main boolean false
15811 This option is available only when Exim is built with an embedded Perl
15812 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15815 .option perl_startup main string unset
15817 This option is available only when Exim is built with an embedded Perl
15818 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15820 .option perl_startup main boolean false
15822 This Option enables the taint mode of the embedded Perl interpreter.
15825 .option pgsql_servers main "string list" unset
15826 .cindex "PostgreSQL lookup type" "server list"
15827 This option provides a list of PostgreSQL servers and associated connection
15828 data, to be used in conjunction with &(pgsql)& lookups (see section
15829 &<<SECID72>>&). The option is available only if Exim has been built with
15830 PostgreSQL support.
15833 .option pid_file_path main string&!! "set at compile time"
15834 .cindex "daemon" "pid file path"
15835 .cindex "pid file, path for"
15836 This option sets the name of the file to which the Exim daemon writes its
15837 process id. The string is expanded, so it can contain, for example, references
15840 pid_file_path = /var/log/$primary_hostname/exim.pid
15842 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
15844 The value set by the option can be overridden by the &%-oP%& command line
15845 option. A pid file is not written if a &"non-standard"& daemon is run by means
15846 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
15849 .option pipelining_advertise_hosts main "host list&!!" *
15850 .cindex "PIPELINING" "suppressing advertising"
15851 This option can be used to suppress the advertisement of the SMTP
15852 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
15853 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
15854 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
15855 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
15856 that clients will use it; &"out of order"& commands that are &"expected"& do
15857 not count as protocol errors (see &%smtp_max_synprot_errors%&).
15860 .option prdr_enable main boolean false
15861 .cindex "PRDR" "enabling on server"
15862 This option can be used to enable the Per-Recipient Data Response extension
15863 to SMTP, defined by Eric Hall.
15864 If the option is set, PRDR is advertised by Exim when operating as a server.
15865 If the client requests PRDR, and more than one recipient, for a message
15866 an additional ACL is called for each recipient after the message content
15867 is received. See section &<<SECTPRDRACL>>&.
15869 .option preserve_message_logs main boolean false
15870 .cindex "message logs" "preserving"
15871 If this option is set, message log files are not deleted when messages are
15872 completed. Instead, they are moved to a sub-directory of the spool directory
15873 called &_msglog.OLD_&, where they remain available for statistical or debugging
15874 purposes. This is a dangerous option to set on systems with any appreciable
15875 volume of mail. Use with care!
15878 .option primary_hostname main string "see below"
15879 .cindex "name" "of local host"
15880 .cindex "host" "name of local"
15881 .cindex "local host" "name of"
15882 .vindex "&$primary_hostname$&"
15883 This specifies the name of the current host. It is used in the default EHLO or
15884 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
15885 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
15886 The value is also used by default in some SMTP response messages from an Exim
15887 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
15889 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
15890 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
15891 contains only one component, Exim passes it to &[gethostbyname()]& (or
15892 &[getipnodebyname()]& when available) in order to obtain the fully qualified
15893 version. The variable &$primary_hostname$& contains the host name, whether set
15894 explicitly by this option, or defaulted.
15897 .option print_topbitchars main boolean false
15898 .cindex "printing characters"
15899 .cindex "8-bit characters"
15900 By default, Exim considers only those characters whose codes lie in the range
15901 32&--126 to be printing characters. In a number of circumstances (for example,
15902 when writing log entries) non-printing characters are converted into escape
15903 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
15904 is set, code values of 128 and above are also considered to be printing
15907 This option also affects the header syntax checks performed by the
15908 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
15909 the user's full name when constructing From: and Sender: addresses (as
15910 described in section &<<SECTconstr>>&). Setting this option can cause
15911 Exim to generate eight bit message headers that do not conform to the
15915 .option process_log_path main string unset
15916 .cindex "process log path"
15917 .cindex "log" "process log"
15918 .cindex "&'exiwhat'&"
15919 This option sets the name of the file to which an Exim process writes its
15920 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
15921 utility script. If this option is unset, the file called &_exim-process.info_&
15922 in Exim's spool directory is used. The ability to specify the name explicitly
15923 can be useful in environments where two different Exims are running, using
15924 different spool directories.
15927 .option prod_requires_admin main boolean true
15931 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
15932 admin user unless &%prod_requires_admin%& is set false. See also
15933 &%queue_list_requires_admin%&.
15936 .option qualify_domain main string "see below"
15937 .cindex "domain" "for qualifying addresses"
15938 .cindex "address" "qualification"
15939 This option specifies the domain name that is added to any envelope sender
15940 addresses that do not have a domain qualification. It also applies to
15941 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
15942 are accepted by default only for locally-generated messages. Qualification is
15943 also applied to addresses in header lines such as &'From:'& and &'To:'& for
15944 locally-generated messages, unless the &%-bnq%& command line option is used.
15946 Messages from external sources must always contain fully qualified addresses,
15947 unless the sending host matches &%sender_unqualified_hosts%& or
15948 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
15949 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
15950 necessary. Internally, Exim always works with fully qualified envelope
15951 addresses. If &%qualify_domain%& is not set, it defaults to the
15952 &%primary_hostname%& value.
15955 .option qualify_recipient main string "see below"
15956 This option allows you to specify a different domain for qualifying recipient
15957 addresses to the one that is used for senders. See &%qualify_domain%& above.
15961 .option queue_domains main "domain list&!!" unset
15962 .cindex "domain" "specifying non-immediate delivery"
15963 .cindex "queueing incoming messages"
15964 .cindex "message" "queueing certain domains"
15965 This option lists domains for which immediate delivery is not required.
15966 A delivery process is started whenever a message is received, but only those
15967 domains that do not match are processed. All other deliveries wait until the
15968 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
15971 .option queue_list_requires_admin main boolean true
15973 The &%-bp%& command-line option, which lists the messages that are on the
15974 queue, requires the caller to be an admin user unless
15975 &%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
15978 .option queue_only main boolean false
15979 .cindex "queueing incoming messages"
15980 .cindex "message" "queueing unconditionally"
15981 If &%queue_only%& is set, a delivery process is not automatically started
15982 whenever a message is received. Instead, the message waits on the queue for the
15983 next queue run. Even if &%queue_only%& is false, incoming messages may not get
15984 delivered immediately when certain conditions (such as heavy load) occur.
15986 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
15987 and &%-odi%& command line options override &%queue_only%& unless
15988 &%queue_only_override%& is set false. See also &%queue_only_file%&,
15989 &%queue_only_load%&, and &%smtp_accept_queue%&.
15992 .option queue_only_file main string unset
15993 .cindex "queueing incoming messages"
15994 .cindex "message" "queueing by file existence"
15995 This option can be set to a colon-separated list of absolute path names, each
15996 one optionally preceded by &"smtp"&. When Exim is receiving a message,
15997 it tests for the existence of each listed path using a call to &[stat()]&. For
15998 each path that exists, the corresponding queueing option is set.
15999 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
16000 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
16002 queue_only_file = smtp/some/file
16004 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
16005 &_/some/file_& exists.
16008 .option queue_only_load main fixed-point unset
16009 .cindex "load average"
16010 .cindex "queueing incoming messages"
16011 .cindex "message" "queueing by load"
16012 If the system load average is higher than this value, incoming messages from
16013 all sources are queued, and no automatic deliveries are started. If this
16014 happens during local or remote SMTP input, all subsequent messages received on
16015 the same SMTP connection are queued by default, whatever happens to the load in
16016 the meantime, but this can be changed by setting &%queue_only_load_latch%&
16019 Deliveries will subsequently be performed by queue runner processes. This
16020 option has no effect on ancient operating systems on which Exim cannot
16021 determine the load average. See also &%deliver_queue_load_max%& and
16022 &%smtp_load_reserve%&.
16025 .option queue_only_load_latch main boolean true
16026 .cindex "load average" "re-evaluating per message"
16027 When this option is true (the default), once one message has been queued
16028 because the load average is higher than the value set by &%queue_only_load%&,
16029 all subsequent messages received on the same SMTP connection are also queued.
16030 This is a deliberate choice; even though the load average may fall below the
16031 threshold, it doesn't seem right to deliver later messages on the same
16032 connection when not delivering earlier ones. However, there are special
16033 circumstances such as very long-lived connections from scanning appliances
16034 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
16035 should be set false. This causes the value of the load average to be
16036 re-evaluated for each message.
16039 .option queue_only_override main boolean true
16040 .cindex "queueing incoming messages"
16041 When this option is true, the &%-od%&&'x'& command line options override the
16042 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
16043 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
16044 to override; they are accepted, but ignored.
16047 .option queue_run_in_order main boolean false
16048 .cindex "queue runner" "processing messages in order"
16049 If this option is set, queue runs happen in order of message arrival instead of
16050 in an arbitrary order. For this to happen, a complete list of the entire queue
16051 must be set up before the deliveries start. When the queue is all held in a
16052 single directory (the default), a single list is created for both the ordered
16053 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
16054 single list is not created when &%queue_run_in_order%& is false. In this case,
16055 the sub-directories are processed one at a time (in a random order), and this
16056 avoids setting up one huge list for the whole queue. Thus, setting
16057 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
16058 when the queue is large, because of the extra work in setting up the single,
16059 large list. In most situations, &%queue_run_in_order%& should not be set.
16063 .option queue_run_max main integer&!! 5
16064 .cindex "queue runner" "maximum number of"
16065 This controls the maximum number of queue runner processes that an Exim daemon
16066 can run simultaneously. This does not mean that it starts them all at once,
16067 but rather that if the maximum number are still running when the time comes to
16068 start another one, it refrains from starting another one. This can happen with
16069 very large queues and/or very sluggish deliveries. This option does not,
16070 however, interlock with other processes, so additional queue runners can be
16071 started by other means, or by killing and restarting the daemon.
16073 Setting this option to zero does not suppress queue runs; rather, it disables
16074 the limit, allowing any number of simultaneous queue runner processes to be
16075 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
16076 the daemon's command line.
16078 .cindex queues named
16079 .cindex "named queues"
16080 To set limits for different named queues use
16081 an expansion depending on the &$queue_name$& variable.
16083 .option queue_smtp_domains main "domain list&!!" unset
16084 .cindex "queueing incoming messages"
16085 .cindex "message" "queueing remote deliveries"
16086 When this option is set, a delivery process is started whenever a message is
16087 received, routing is performed, and local deliveries take place.
16088 However, if any SMTP deliveries are required for domains that match
16089 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
16090 message waits on the queue for the next queue run. Since routing of the message
16091 has taken place, Exim knows to which remote hosts it must be delivered, and so
16092 when the queue run happens, multiple messages for the same host are delivered
16093 over a single SMTP connection. The &%-odqs%& command line option causes all
16094 SMTP deliveries to be queued in this way, and is equivalent to setting
16095 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
16099 .option receive_timeout main time 0s
16100 .cindex "timeout" "for non-SMTP input"
16101 This option sets the timeout for accepting a non-SMTP message, that is, the
16102 maximum time that Exim waits when reading a message on the standard input. If
16103 the value is zero, it will wait for ever. This setting is overridden by the
16104 &%-or%& command line option. The timeout for incoming SMTP messages is
16105 controlled by &%smtp_receive_timeout%&.
16107 .option received_header_text main string&!! "see below"
16108 .cindex "customizing" "&'Received:'& header"
16109 .cindex "&'Received:'& header line" "customizing"
16110 This string defines the contents of the &'Received:'& message header that is
16111 added to each message, except for the timestamp, which is automatically added
16112 on at the end (preceded by a semicolon). The string is expanded each time it is
16113 used. If the expansion yields an empty string, no &'Received:'& header line is
16114 added to the message. Otherwise, the string should start with the text
16115 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
16116 header lines. The default setting is:
16119 received_header_text = Received: \
16120 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
16121 {${if def:sender_ident \
16122 {from ${quote_local_part:$sender_ident} }}\
16123 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
16124 by $primary_hostname \
16125 ${if def:received_protocol {with $received_protocol}} \
16126 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
16127 (Exim $version_number)\n\t\
16128 ${if def:sender_address \
16129 {(envelope-from <$sender_address>)\n\t}}\
16130 id $message_exim_id\
16131 ${if def:received_for {\n\tfor $received_for}}
16134 The reference to the TLS cipher is omitted when Exim is built without TLS
16135 support. The use of conditional expansions ensures that this works for both
16136 locally generated messages and messages received from remote hosts, giving
16137 header lines such as the following:
16139 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
16140 by marley.carol.example with esmtp (Exim 4.00)
16141 (envelope-from <bob@carol.example>)
16142 id 16IOWa-00019l-00
16143 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
16144 Received: by scrooge.carol.example with local (Exim 4.00)
16145 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
16147 Until the body of the message has been received, the timestamp is the time when
16148 the message started to be received. Once the body has arrived, and all policy
16149 checks have taken place, the timestamp is updated to the time at which the
16150 message was accepted.
16153 .option received_headers_max main integer 30
16154 .cindex "loop" "prevention"
16155 .cindex "mail loop prevention"
16156 .cindex "&'Received:'& header line" "counting"
16157 When a message is to be delivered, the number of &'Received:'& headers is
16158 counted, and if it is greater than this parameter, a mail loop is assumed to
16159 have occurred, the delivery is abandoned, and an error message is generated.
16160 This applies to both local and remote deliveries.
16163 .option recipient_unqualified_hosts main "host list&!!" unset
16164 .cindex "unqualified addresses"
16165 .cindex "host" "unqualified addresses from"
16166 This option lists those hosts from which Exim is prepared to accept unqualified
16167 recipient addresses in message envelopes. The addresses are made fully
16168 qualified by the addition of the &%qualify_recipient%& value. This option also
16169 affects message header lines. Exim does not reject unqualified recipient
16170 addresses in headers, but it qualifies them only if the message came from a
16171 host that matches &%recipient_unqualified_hosts%&,
16172 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
16173 option was not set.
16176 .option recipients_max main integer 0
16177 .cindex "limit" "number of recipients"
16178 .cindex "recipient" "maximum number"
16179 If this option is set greater than zero, it specifies the maximum number of
16180 original recipients for any message. Additional recipients that are generated
16181 by aliasing or forwarding do not count. SMTP messages get a 452 response for
16182 all recipients over the limit; earlier recipients are delivered as normal.
16183 Non-SMTP messages with too many recipients are failed, and no deliveries are
16186 .cindex "RCPT" "maximum number of incoming"
16187 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
16188 RCPT commands in a single message.
16191 .option recipients_max_reject main boolean false
16192 If this option is set true, Exim rejects SMTP messages containing too many
16193 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16194 error to the eventual DATA command. Otherwise (the default) it gives a 452
16195 error to the surplus RCPT commands and accepts the message on behalf of the
16196 initial set of recipients. The remote server should then re-send the message
16197 for the remaining recipients at a later time.
16200 .option remote_max_parallel main integer 2
16201 .cindex "delivery" "parallelism for remote"
16202 This option controls parallel delivery of one message to a number of remote
16203 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16204 does all the remote deliveries for a message one by one. Otherwise, if a single
16205 message has to be delivered to more than one remote host, or if several copies
16206 have to be sent to the same remote host, up to &%remote_max_parallel%&
16207 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16208 deliveries are required, the maximum number of processes are started, and as
16209 each one finishes, another is begun. The order of starting processes is the
16210 same as if sequential delivery were being done, and can be controlled by the
16211 &%remote_sort_domains%& option. If parallel delivery takes place while running
16212 with debugging turned on, the debugging output from each delivery process is
16213 tagged with its process id.
16215 This option controls only the maximum number of parallel deliveries for one
16216 message in one Exim delivery process. Because Exim has no central queue
16217 manager, there is no way of controlling the total number of simultaneous
16218 deliveries if the configuration allows a delivery attempt as soon as a message
16221 .cindex "number of deliveries"
16222 .cindex "delivery" "maximum number of"
16223 If you want to control the total number of deliveries on the system, you
16224 need to set the &%queue_only%& option. This ensures that all incoming messages
16225 are added to the queue without starting a delivery process. Then set up an Exim
16226 daemon to start queue runner processes at appropriate intervals (probably
16227 fairly often, for example, every minute), and limit the total number of queue
16228 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16229 delivers only one message at a time, the maximum number of deliveries that can
16230 then take place at once is &%queue_run_max%& multiplied by
16231 &%remote_max_parallel%&.
16233 If it is purely remote deliveries you want to control, use
16234 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16235 doing the SMTP routing before queueing, so that several messages for the same
16236 host will eventually get delivered down the same connection.
16239 .option remote_sort_domains main "domain list&!!" unset
16240 .cindex "sorting remote deliveries"
16241 .cindex "delivery" "sorting remote"
16242 When there are a number of remote deliveries for a message, they are sorted by
16243 domain into the order given by this list. For example,
16245 remote_sort_domains = *.cam.ac.uk:*.uk
16247 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16248 then to those in the &%uk%& domain, then to any others.
16251 .option retry_data_expire main time 7d
16252 .cindex "hints database" "data expiry"
16253 This option sets a &"use before"& time on retry information in Exim's hints
16254 database. Any older retry data is ignored. This means that, for example, once a
16255 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16259 .option retry_interval_max main time 24h
16260 .cindex "retry" "limit on interval"
16261 .cindex "limit" "on retry interval"
16262 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16263 intervals between delivery attempts for messages that cannot be delivered
16264 straight away. This option sets an overall limit to the length of time between
16265 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16269 .option return_path_remove main boolean true
16270 .cindex "&'Return-path:'& header line" "removing"
16271 RFC 2821, section 4.4, states that an SMTP server must insert a
16272 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16273 The &'Return-path:'& header preserves the sender address as received in the
16274 MAIL command. This description implies that this header should not be present
16275 in an incoming message. If &%return_path_remove%& is true, any existing
16276 &'Return-path:'& headers are removed from messages at the time they are
16277 received. Exim's transports have options for adding &'Return-path:'& headers at
16278 the time of delivery. They are normally used only for final local deliveries.
16281 .option return_size_limit main integer 100K
16282 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16285 .option rfc1413_hosts main "host list&!!" @[]
16287 .cindex "host" "for RFC 1413 calls"
16288 RFC 1413 identification calls are made to any client host which matches
16289 an item in the list.
16290 The default value specifies just this host, being any local interface
16293 .option rfc1413_query_timeout main time 0s
16294 .cindex "RFC 1413" "query timeout"
16295 .cindex "timeout" "for RFC 1413 call"
16296 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16297 no RFC 1413 calls are ever made.
16300 .option sender_unqualified_hosts main "host list&!!" unset
16301 .cindex "unqualified addresses"
16302 .cindex "host" "unqualified addresses from"
16303 This option lists those hosts from which Exim is prepared to accept unqualified
16304 sender addresses. The addresses are made fully qualified by the addition of
16305 &%qualify_domain%&. This option also affects message header lines. Exim does
16306 not reject unqualified addresses in headers that contain sender addresses, but
16307 it qualifies them only if the message came from a host that matches
16308 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16309 using TCP/IP), and the &%-bnq%& option was not set.
16311 .option set_environment main "string list" empty
16312 .cindex "environment"
16313 This option allows to set individual environment variables that the
16314 currently linked libraries and programs in child processes use. The
16315 default list is empty,
16318 .option slow_lookup_log main integer 0
16319 .cindex "logging" "slow lookups"
16320 .cindex "dns" "logging slow lookups"
16321 This option controls logging of slow lookups.
16322 If the value is nonzero it is taken as a number of milliseconds
16323 and lookups taking longer than this are logged.
16324 Currently this applies only to DNS lookups.
16328 .option smtp_accept_keepalive main boolean true
16329 .cindex "keepalive" "on incoming connection"
16330 This option controls the setting of the SO_KEEPALIVE option on incoming
16331 TCP/IP socket connections. When set, it causes the kernel to probe idle
16332 connections periodically, by sending packets with &"old"& sequence numbers. The
16333 other end of the connection should send an acknowledgment if the connection is
16334 still okay or a reset if the connection has been aborted. The reason for doing
16335 this is that it has the beneficial effect of freeing up certain types of
16336 connection that can get stuck when the remote host is disconnected without
16337 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16338 hours to detect unreachable hosts.
16342 .option smtp_accept_max main integer 20
16343 .cindex "limit" "incoming SMTP connections"
16344 .cindex "SMTP" "incoming connection count"
16346 This option specifies the maximum number of simultaneous incoming SMTP calls
16347 that Exim will accept. It applies only to the listening daemon; there is no
16348 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16349 value is set to zero, no limit is applied. However, it is required to be
16350 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16351 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16353 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16354 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16355 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16356 and &%smtp_load_reserve%& are then checked before accepting the connection.
16359 .option smtp_accept_max_nonmail main integer 10
16360 .cindex "limit" "non-mail SMTP commands"
16361 .cindex "SMTP" "limiting non-mail commands"
16362 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16363 the connection if there are too many. This option defines &"too many"&. The
16364 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16365 client looping sending EHLO, for example. The check is applied only if the
16366 client host matches &%smtp_accept_max_nonmail_hosts%&.
16368 When a new message is expected, one occurrence of RSET is not counted. This
16369 allows a client to send one RSET between messages (this is not necessary,
16370 but some clients do it). Exim also allows one uncounted occurrence of HELO
16371 or EHLO, and one occurrence of STARTTLS between messages. After
16372 starting up a TLS session, another EHLO is expected, and so it too is not
16373 counted. The first occurrence of AUTH in a connection, or immediately
16374 following STARTTLS is not counted. Otherwise, all commands other than
16375 MAIL, RCPT, DATA, and QUIT are counted.
16378 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16379 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16380 check by setting this option. The default value makes it apply to all hosts. By
16381 changing the value, you can exclude any badly-behaved hosts that you have to
16385 . Allow this long option name to split; give it unsplit as a fifth argument
16386 . for the automatic .oindex that is generated by .option.
16387 . We insert " &~&~" which is both pretty nasty visually and results in
16388 . non-searchable text. HowItWorks.txt mentions an option for inserting
16389 . zero-width-space, which would be nicer visually and results in (at least)
16390 . html that Firefox will split on when it's forced to reflow (rather than
16391 . inserting a horizontal scrollbar). However, the text is still not
16392 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16393 . the option name to split.
16395 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16396 smtp_accept_max_per_connection
16397 .cindex "SMTP" "limiting incoming message count"
16398 .cindex "limit" "messages per SMTP connection"
16399 The value of this option limits the number of MAIL commands that Exim is
16400 prepared to accept over a single SMTP connection, whether or not each command
16401 results in the transfer of a message. After the limit is reached, a 421
16402 response is given to subsequent MAIL commands. This limit is a safety
16403 precaution against a client that goes mad (incidents of this type have been
16407 .option smtp_accept_max_per_host main string&!! unset
16408 .cindex "limit" "SMTP connections from one host"
16409 .cindex "host" "limiting SMTP connections from"
16410 This option restricts the number of simultaneous IP connections from a single
16411 host (strictly, from a single IP address) to the Exim daemon. The option is
16412 expanded, to enable different limits to be applied to different hosts by
16413 reference to &$sender_host_address$&. Once the limit is reached, additional
16414 connection attempts from the same host are rejected with error code 421. This
16415 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16416 of zero imposes no limit. If this option is set greater than zero, it is
16417 required that &%smtp_accept_max%& be non-zero.
16419 &*Warning*&: When setting this option you should not use any expansion
16420 constructions that take an appreciable amount of time. The expansion and test
16421 happen in the main daemon loop, in order to reject additional connections
16422 without forking additional processes (otherwise a denial-of-service attack
16423 could cause a vast number or processes to be created). While the daemon is
16424 doing this processing, it cannot accept any other incoming connections.
16428 .option smtp_accept_queue main integer 0
16429 .cindex "SMTP" "incoming connection count"
16430 .cindex "queueing incoming messages"
16431 .cindex "message" "queueing by SMTP connection count"
16432 If the number of simultaneous incoming SMTP connections being handled via the
16433 listening daemon exceeds this value, messages received by SMTP are just placed
16434 on the queue; no delivery processes are started automatically. The count is
16435 fixed at the start of an SMTP connection. It cannot be updated in the
16436 subprocess that receives messages, and so the queueing or not queueing applies
16437 to all messages received in the same connection.
16439 A value of zero implies no limit, and clearly any non-zero value is useful only
16440 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16441 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16442 various &%-od%&&'x'& command line options.
16445 . See the comment on smtp_accept_max_per_connection
16447 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16448 smtp_accept_queue_per_connection
16449 .cindex "queueing incoming messages"
16450 .cindex "message" "queueing by message count"
16451 This option limits the number of delivery processes that Exim starts
16452 automatically when receiving messages via SMTP, whether via the daemon or by
16453 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16454 and the number of messages received in a single SMTP session exceeds this
16455 number, subsequent messages are placed on the queue, but no delivery processes
16456 are started. This helps to limit the number of Exim processes when a server
16457 restarts after downtime and there is a lot of mail waiting for it on other
16458 systems. On large systems, the default should probably be increased, and on
16459 dial-in client systems it should probably be set to zero (that is, disabled).
16462 .option smtp_accept_reserve main integer 0
16463 .cindex "SMTP" "incoming call count"
16464 .cindex "host" "reserved"
16465 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16466 number of SMTP connections that are reserved for connections from the hosts
16467 that are specified in &%smtp_reserve_hosts%&. The value set in
16468 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16469 restricted to this number of connections; the option specifies a minimum number
16470 of connection slots for them, not a maximum. It is a guarantee that this group
16471 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16472 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16475 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16476 set to 5, once there are 45 active connections (from any hosts), new
16477 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16478 provided the other criteria for acceptance are met.
16481 .option smtp_active_hostname main string&!! unset
16482 .cindex "host" "name in SMTP responses"
16483 .cindex "SMTP" "host name in responses"
16484 .vindex "&$primary_hostname$&"
16485 This option is provided for multi-homed servers that want to masquerade as
16486 several different hosts. At the start of an incoming SMTP connection, its value
16487 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16488 responses. For example, it is used as domain name in the response to an
16489 incoming HELO or EHLO command.
16491 .vindex "&$smtp_active_hostname$&"
16492 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16493 is saved with any messages that are received. It is therefore available for use
16494 in routers and transports when the message is later delivered.
16496 If this option is unset, or if its expansion is forced to fail, or if the
16497 expansion results in an empty string, the value of &$primary_hostname$& is
16498 used. Other expansion failures cause a message to be written to the main and
16499 panic logs, and the SMTP command receives a temporary error. Typically, the
16500 value of &%smtp_active_hostname%& depends on the incoming interface address.
16503 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16504 {cox.mydomain}{box.mydomain}}
16507 Although &$smtp_active_hostname$& is primarily concerned with incoming
16508 messages, it is also used as the default for HELO commands in callout
16509 verification if there is no remote transport from which to obtain a
16510 &%helo_data%& value.
16512 .option smtp_banner main string&!! "see below"
16513 .cindex "SMTP" "welcome banner"
16514 .cindex "banner for SMTP"
16515 .cindex "welcome banner for SMTP"
16516 .cindex "customizing" "SMTP banner"
16517 This string, which is expanded every time it is used, is output as the initial
16518 positive response to an SMTP connection. The default setting is:
16520 smtp_banner = $smtp_active_hostname ESMTP Exim \
16521 $version_number $tod_full
16523 Failure to expand the string causes a panic error. If you want to create a
16524 multiline response to the initial SMTP connection, use &"\n"& in the string at
16525 appropriate points, but not at the end. Note that the 220 code is not included
16526 in this string. Exim adds it automatically (several times in the case of a
16527 multiline response).
16530 .option smtp_check_spool_space main boolean true
16531 .cindex "checking disk space"
16532 .cindex "disk space, checking"
16533 .cindex "spool directory" "checking space"
16534 When this option is set, if an incoming SMTP session encounters the SIZE
16535 option on a MAIL command, it checks that there is enough space in the
16536 spool directory's partition to accept a message of that size, while still
16537 leaving free the amount specified by &%check_spool_space%& (even if that value
16538 is zero). If there isn't enough space, a temporary error code is returned.
16541 .option smtp_connect_backlog main integer 20
16542 .cindex "connection backlog"
16543 .cindex "SMTP" "connection backlog"
16544 .cindex "backlog of connections"
16545 This option specifies a maximum number of waiting SMTP connections. Exim passes
16546 this value to the TCP/IP system when it sets up its listener. Once this number
16547 of connections are waiting for the daemon's attention, subsequent connection
16548 attempts are refused at the TCP/IP level. At least, that is what the manuals
16549 say; in some circumstances such connection attempts have been observed to time
16550 out instead. For large systems it is probably a good idea to increase the
16551 value (to 50, say). It also gives some protection against denial-of-service
16552 attacks by SYN flooding.
16555 .option smtp_enforce_sync main boolean true
16556 .cindex "SMTP" "synchronization checking"
16557 .cindex "synchronization checking in SMTP"
16558 The SMTP protocol specification requires the client to wait for a response from
16559 the server at certain points in the dialogue. Without PIPELINING these
16560 synchronization points are after every command; with PIPELINING they are
16561 fewer, but they still exist.
16563 Some spamming sites send out a complete set of SMTP commands without waiting
16564 for any response. Exim protects against this by rejecting a message if the
16565 client has sent further input when it should not have. The error response &"554
16566 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16567 for this error cannot be perfect because of transmission delays (unexpected
16568 input may be on its way but not yet received when Exim checks). However, it
16569 does detect many instances.
16571 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16572 If you want to disable the check selectively (for example, only for certain
16573 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16574 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16578 .option smtp_etrn_command main string&!! unset
16579 .cindex "ETRN" "command to be run"
16580 .vindex "&$domain$&"
16581 If this option is set, the given command is run whenever an SMTP ETRN
16582 command is received from a host that is permitted to issue such commands (see
16583 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16584 are independently expanded. The expansion variable &$domain$& is set to the
16585 argument of the ETRN command, and no syntax checking is done on it. For
16588 smtp_etrn_command = /etc/etrn_command $domain \
16589 $sender_host_address
16591 A new process is created to run the command, but Exim does not wait for it to
16592 complete. Consequently, its status cannot be checked. If the command cannot be
16593 run, a line is written to the panic log, but the ETRN caller still receives
16594 a 250 success response. Exim is normally running under its own uid when
16595 receiving SMTP, so it is not possible for it to change the uid before running
16599 .option smtp_etrn_serialize main boolean true
16600 .cindex "ETRN" "serializing"
16601 When this option is set, it prevents the simultaneous execution of more than
16602 one identical command as a result of ETRN in an SMTP connection. See
16603 section &<<SECTETRN>>& for details.
16606 .option smtp_load_reserve main fixed-point unset
16607 .cindex "load average"
16608 If the system load average ever gets higher than this, incoming SMTP calls are
16609 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16610 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16611 the load is over the limit. The option has no effect on ancient operating
16612 systems on which Exim cannot determine the load average. See also
16613 &%deliver_queue_load_max%& and &%queue_only_load%&.
16617 .option smtp_max_synprot_errors main integer 3
16618 .cindex "SMTP" "limiting syntax and protocol errors"
16619 .cindex "limit" "SMTP syntax and protocol errors"
16620 Exim rejects SMTP commands that contain syntax or protocol errors. In
16621 particular, a syntactically invalid email address, as in this command:
16623 RCPT TO:<abc xyz@a.b.c>
16625 causes immediate rejection of the command, before any other tests are done.
16626 (The ACL cannot be run if there is no valid address to set up for it.) An
16627 example of a protocol error is receiving RCPT before MAIL. If there are
16628 too many syntax or protocol errors in one SMTP session, the connection is
16629 dropped. The limit is set by this option.
16631 .cindex "PIPELINING" "expected errors"
16632 When the PIPELINING extension to SMTP is in use, some protocol errors are
16633 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16634 Exim assumes that PIPELINING will be used if it advertises it (see
16635 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16636 not count towards the limit.
16640 .option smtp_max_unknown_commands main integer 3
16641 .cindex "SMTP" "limiting unknown commands"
16642 .cindex "limit" "unknown SMTP commands"
16643 If there are too many unrecognized commands in an incoming SMTP session, an
16644 Exim server drops the connection. This is a defence against some kinds of abuse
16647 into making connections to SMTP ports; in these circumstances, a number of
16648 non-SMTP command lines are sent first.
16652 .option smtp_ratelimit_hosts main "host list&!!" unset
16653 .cindex "SMTP" "rate limiting"
16654 .cindex "limit" "rate of message arrival"
16655 .cindex "RCPT" "rate limiting"
16656 Some sites find it helpful to be able to limit the rate at which certain hosts
16657 can send them messages, and the rate at which an individual message can specify
16660 Exim has two rate-limiting facilities. This section describes the older
16661 facility, which can limit rates within a single connection. The newer
16662 &%ratelimit%& ACL condition can limit rates across all connections. See section
16663 &<<SECTratelimiting>>& for details of the newer facility.
16665 When a host matches &%smtp_ratelimit_hosts%&, the values of
16666 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16667 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16668 respectively. Each option, if set, must contain a set of four comma-separated
16672 A threshold, before which there is no rate limiting.
16674 An initial time delay. Unlike other times in Exim, numbers with decimal
16675 fractional parts are allowed here.
16677 A factor by which to increase the delay each time.
16679 A maximum value for the delay. This should normally be less than 5 minutes,
16680 because after that time, the client is liable to timeout the SMTP command.
16683 For example, these settings have been used successfully at the site which
16684 first suggested this feature, for controlling mail from their customers:
16686 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16687 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16689 The first setting specifies delays that are applied to MAIL commands after
16690 two have been received over a single connection. The initial delay is 0.5
16691 seconds, increasing by a factor of 1.05 each time. The second setting applies
16692 delays to RCPT commands when more than four occur in a single message.
16695 .option smtp_ratelimit_mail main string unset
16696 See &%smtp_ratelimit_hosts%& above.
16699 .option smtp_ratelimit_rcpt main string unset
16700 See &%smtp_ratelimit_hosts%& above.
16703 .option smtp_receive_timeout main time&!! 5m
16704 .cindex "timeout" "for SMTP input"
16705 .cindex "SMTP" "input timeout"
16706 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16707 input, including batch SMTP. If a line of input (either an SMTP command or a
16708 data line) is not received within this time, the SMTP connection is dropped and
16709 the message is abandoned.
16710 A line is written to the log containing one of the following messages:
16712 SMTP command timeout on connection from...
16713 SMTP data timeout on connection from...
16715 The former means that Exim was expecting to read an SMTP command; the latter
16716 means that it was in the DATA phase, reading the contents of a message.
16718 If the first character of the option is a &"$"& the option is
16719 expanded before use and may depend on
16720 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16724 The value set by this option can be overridden by the
16725 &%-os%& command-line option. A setting of zero time disables the timeout, but
16726 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16727 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16728 timeout is controlled by &%receive_timeout%& and &%-or%&.
16731 .option smtp_reserve_hosts main "host list&!!" unset
16732 This option defines hosts for which SMTP connections are reserved; see
16733 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16736 .option smtp_return_error_details main boolean false
16737 .cindex "SMTP" "details policy failures"
16738 .cindex "policy control" "rejection, returning details"
16739 In the default state, Exim uses bland messages such as
16740 &"Administrative prohibition"& when it rejects SMTP commands for policy
16741 reasons. Many sysadmins like this because it gives away little information
16742 to spammers. However, some other sysadmins who are applying strict checking
16743 policies want to give out much fuller information about failures. Setting
16744 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16745 example, instead of &"Administrative prohibition"&, it might give:
16747 550-Rejected after DATA: '>' missing at end of address:
16748 550 failing address in "From" header is: <user@dom.ain
16752 .option smtputf8_advertise_hosts main "host list&!!" *
16753 .cindex "SMTPUTF8" "advertising"
16754 When Exim is built with support for internationalised mail names,
16755 the availability thereof is advertised in
16756 response to EHLO only to those client hosts that match this option. See
16757 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
16760 .option spamd_address main string "see below"
16761 This option is available when Exim is compiled with the content-scanning
16762 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16763 The default value is
16767 See section &<<SECTscanspamass>>& for more details.
16771 .option split_spool_directory main boolean false
16772 .cindex "multiple spool directories"
16773 .cindex "spool directory" "split"
16774 .cindex "directories, multiple"
16775 If this option is set, it causes Exim to split its input directory into 62
16776 subdirectories, each with a single alphanumeric character as its name. The
16777 sixth character of the message id is used to allocate messages to
16778 subdirectories; this is the least significant base-62 digit of the time of
16779 arrival of the message.
16781 Splitting up the spool in this way may provide better performance on systems
16782 where there are long mail queues, by reducing the number of files in any one
16783 directory. The msglog directory is also split up in a similar way to the input
16784 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16785 are still placed in the single directory &_msglog.OLD_&.
16787 It is not necessary to take any special action for existing messages when
16788 changing &%split_spool_directory%&. Exim notices messages that are in the
16789 &"wrong"& place, and continues to process them. If the option is turned off
16790 after a period of being on, the subdirectories will eventually empty and be
16791 automatically deleted.
16793 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16794 changes. Instead of creating a list of all messages in the queue, and then
16795 trying to deliver each one in turn, it constructs a list of those in one
16796 sub-directory and tries to deliver them, before moving on to the next
16797 sub-directory. The sub-directories are processed in a random order. This
16798 spreads out the scanning of the input directories, and uses less memory. It is
16799 particularly beneficial when there are lots of messages on the queue. However,
16800 if &%queue_run_in_order%& is set, none of this new processing happens. The
16801 entire queue has to be scanned and sorted before any deliveries can start.
16804 .option spool_directory main string&!! "set at compile time"
16805 .cindex "spool directory" "path to"
16806 This defines the directory in which Exim keeps its spool, that is, the messages
16807 it is waiting to deliver. The default value is taken from the compile-time
16808 configuration setting, if there is one. If not, this option must be set. The
16809 string is expanded, so it can contain, for example, a reference to
16810 &$primary_hostname$&.
16812 If the spool directory name is fixed on your installation, it is recommended
16813 that you set it at build time rather than from this option, particularly if the
16814 log files are being written to the spool directory (see &%log_file_path%&).
16815 Otherwise log files cannot be used for errors that are detected early on, such
16816 as failures in the configuration file.
16818 By using this option to override the compiled-in path, it is possible to run
16819 tests of Exim without using the standard spool.
16821 .option sqlite_lock_timeout main time 5s
16822 .cindex "sqlite lookup type" "lock timeout"
16823 This option controls the timeout that the &(sqlite)& lookup uses when trying to
16824 access an SQLite database. See section &<<SECTsqlite>>& for more details.
16826 .option strict_acl_vars main boolean false
16827 .cindex "&ACL;" "variables, handling unset"
16828 This option controls what happens if a syntactically valid but undefined ACL
16829 variable is referenced. If it is false (the default), an empty string
16830 is substituted; if it is true, an error is generated. See section
16831 &<<SECTaclvariables>>& for details of ACL variables.
16833 .option strip_excess_angle_brackets main boolean false
16834 .cindex "angle brackets, excess"
16835 If this option is set, redundant pairs of angle brackets round &"route-addr"&
16836 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
16837 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
16838 passed on to another MTA, the excess angle brackets are not passed on. If this
16839 option is not set, multiple pairs of angle brackets cause a syntax error.
16842 .option strip_trailing_dot main boolean false
16843 .cindex "trailing dot on domain"
16844 .cindex "dot" "trailing on domain"
16845 If this option is set, a trailing dot at the end of a domain in an address is
16846 ignored. If this is in the envelope and the message is passed on to another
16847 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
16848 domain causes a syntax error.
16849 However, addresses in header lines are checked only when an ACL requests header
16853 .option syslog_duplication main boolean true
16854 .cindex "syslog" "duplicate log lines; suppressing"
16855 When Exim is logging to syslog, it writes the log lines for its three
16856 separate logs at different syslog priorities so that they can in principle
16857 be separated on the logging hosts. Some installations do not require this
16858 separation, and in those cases, the duplication of certain log lines is a
16859 nuisance. If &%syslog_duplication%& is set false, only one copy of any
16860 particular log line is written to syslog. For lines that normally go to
16861 both the main log and the reject log, the reject log version (possibly
16862 containing message header lines) is written, at LOG_NOTICE priority.
16863 Lines that normally go to both the main and the panic log are written at
16864 the LOG_ALERT priority.
16867 .option syslog_facility main string unset
16868 .cindex "syslog" "facility; setting"
16869 This option sets the syslog &"facility"& name, used when Exim is logging to
16870 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
16871 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
16872 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
16873 details of Exim's logging.
16876 .option syslog_pid main boolean true
16877 .cindex "syslog" "pid"
16878 If &%syslog_pid%& is set false, the PID on Exim's log lines are
16879 omitted when these lines are sent to syslog. (Syslog normally prefixes
16880 the log lines with the PID of the logging process automatically.) You need
16881 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
16882 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
16886 .option syslog_processname main string &`exim`&
16887 .cindex "syslog" "process name; setting"
16888 This option sets the syslog &"ident"& name, used when Exim is logging to
16889 syslog. The value must be no longer than 32 characters. See chapter
16890 &<<CHAPlog>>& for details of Exim's logging.
16894 .option syslog_timestamp main boolean true
16895 .cindex "syslog" "timestamps"
16896 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
16897 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
16898 details of Exim's logging.
16901 .option system_filter main string&!! unset
16902 .cindex "filter" "system filter"
16903 .cindex "system filter" "specifying"
16904 .cindex "Sieve filter" "not available for system filter"
16905 This option specifies an Exim filter file that is applied to all messages at
16906 the start of each delivery attempt, before any routing is done. System filters
16907 must be Exim filters; they cannot be Sieve filters. If the system filter
16908 generates any deliveries to files or pipes, or any new mail messages, the
16909 appropriate &%system_filter_..._transport%& option(s) must be set, to define
16910 which transports are to be used. Details of this facility are given in chapter
16911 &<<CHAPsystemfilter>>&.
16912 A forced expansion failure results in no filter operation.
16915 .option system_filter_directory_transport main string&!! unset
16916 .vindex "&$address_file$&"
16917 This sets the name of the transport driver that is to be used when the
16918 &%save%& command in a system message filter specifies a path ending in &"/"&,
16919 implying delivery of each message into a separate file in some directory.
16920 During the delivery, the variable &$address_file$& contains the path name.
16923 .option system_filter_file_transport main string&!! unset
16924 .cindex "file" "transport for system filter"
16925 This sets the name of the transport driver that is to be used when the &%save%&
16926 command in a system message filter specifies a path not ending in &"/"&. During
16927 the delivery, the variable &$address_file$& contains the path name.
16929 .option system_filter_group main string unset
16930 .cindex "gid (group id)" "system filter"
16931 This option is used only when &%system_filter_user%& is also set. It sets the
16932 gid under which the system filter is run, overriding any gid that is associated
16933 with the user. The value may be numerical or symbolic.
16935 .option system_filter_pipe_transport main string&!! unset
16936 .cindex "&(pipe)& transport" "for system filter"
16937 .vindex "&$address_pipe$&"
16938 This specifies the transport driver that is to be used when a &%pipe%& command
16939 is used in a system filter. During the delivery, the variable &$address_pipe$&
16940 contains the pipe command.
16943 .option system_filter_reply_transport main string&!! unset
16944 .cindex "&(autoreply)& transport" "for system filter"
16945 This specifies the transport driver that is to be used when a &%mail%& command
16946 is used in a system filter.
16949 .option system_filter_user main string unset
16950 .cindex "uid (user id)" "system filter"
16951 If this option is set to root, the system filter is run in the main Exim
16952 delivery process, as root. Otherwise, the system filter runs in a separate
16953 process, as the given user, defaulting to the Exim run-time user.
16954 Unless the string consists entirely of digits, it
16955 is looked up in the password data. Failure to find the named user causes a
16956 configuration error. The gid is either taken from the password data, or
16957 specified by &%system_filter_group%&. When the uid is specified numerically,
16958 &%system_filter_group%& is required to be set.
16960 If the system filter generates any pipe, file, or reply deliveries, the uid
16961 under which the filter is run is used when transporting them, unless a
16962 transport option overrides.
16965 .option tcp_nodelay main boolean true
16966 .cindex "daemon" "TCP_NODELAY on sockets"
16967 .cindex "Nagle algorithm"
16968 .cindex "TCP_NODELAY on listening sockets"
16969 If this option is set false, it stops the Exim daemon setting the
16970 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
16971 turns off the &"Nagle algorithm"&, which is a way of improving network
16972 performance in interactive (character-by-character) situations. Turning it off
16973 should improve Exim's performance a bit, so that is what happens by default.
16974 However, it appears that some broken clients cannot cope, and time out. Hence
16975 this option. It affects only those sockets that are set up for listening by the
16976 daemon. Sockets created by the smtp transport for delivering mail always set
16980 .option timeout_frozen_after main time 0s
16981 .cindex "frozen messages" "timing out"
16982 .cindex "timeout" "frozen messages"
16983 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
16984 message of any kind that has been on the queue for longer than the given time
16985 is automatically cancelled at the next queue run. If the frozen message is a
16986 bounce message, it is just discarded; otherwise, a bounce is sent to the
16987 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
16988 If you want to timeout frozen bounce messages earlier than other kinds of
16989 frozen message, see &%ignore_bounce_errors_after%&.
16991 &*Note:*& the default value of zero means no timeouts; with this setting,
16992 frozen messages remain on the queue forever (except for any frozen bounce
16993 messages that are released by &%ignore_bounce_errors_after%&).
16996 .option timezone main string unset
16997 .cindex "timezone, setting"
16998 .cindex "environment" "values from"
16999 The value of &%timezone%& is used to set the environment variable TZ while
17000 running Exim (if it is different on entry). This ensures that all timestamps
17001 created by Exim are in the required timezone. If you want all your timestamps
17002 to be in UTC (aka GMT) you should set
17006 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
17007 or, if that is not set, from the value of the TZ environment variable when Exim
17008 is built. If &%timezone%& is set to the empty string, either at build or run
17009 time, any existing TZ variable is removed from the environment when Exim
17010 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
17011 unfortunately not all, operating systems.
17014 .option tls_advertise_hosts main "host list&!!" *
17015 .cindex "TLS" "advertising"
17016 .cindex "encryption" "on SMTP connection"
17017 .cindex "SMTP" "encrypted connection"
17018 When Exim is built with support for TLS encrypted connections, the availability
17019 of the STARTTLS command to set up an encrypted session is advertised in
17020 response to EHLO only to those client hosts that match this option. See
17021 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
17022 Note that the default value requires that a certificate be supplied
17023 using the &%tls_certificate%& option. If TLS support for incoming connections
17024 is not required the &%tls_advertise_hosts%& option should be set empty.
17027 .option tls_certificate main string&!! unset
17028 .cindex "TLS" "server certificate; location of"
17029 .cindex "certificate" "server, location of"
17030 The value of this option is expanded, and must then be the absolute path to a
17031 file which contains the server's certificates. The server's private key is also
17032 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
17033 &<<CHAPTLS>>& for further details.
17035 &*Note*&: The certificates defined by this option are used only when Exim is
17036 receiving incoming messages as a server. If you want to supply certificates for
17037 use when sending messages as a client, you must set the &%tls_certificate%&
17038 option in the relevant &(smtp)& transport.
17040 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
17041 if the OpenSSL build supports TLS extensions and the TLS client sends the
17042 Server Name Indication extension, then this option and others documented in
17043 &<<SECTtlssni>>& will be re-expanded.
17045 If this option is unset or empty a fresh self-signed certificate will be
17046 generated for every connection.
17048 .option tls_crl main string&!! unset
17049 .cindex "TLS" "server certificate revocation list"
17050 .cindex "certificate" "revocation list for server"
17051 This option specifies a certificate revocation list. The expanded value must
17052 be the name of a file that contains a CRL in PEM format.
17054 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17057 .option tls_dh_max_bits main integer 2236
17058 .cindex "TLS" "D-H bit count"
17059 The number of bits used for Diffie-Hellman key-exchange may be suggested by
17060 the chosen TLS library. That value might prove to be too high for
17061 interoperability. This option provides a maximum clamp on the value
17062 suggested, trading off security for interoperability.
17064 The value must be at least 1024.
17066 The value 2236 was chosen because, at time of adding the option, it was the
17067 hard-coded maximum value supported by the NSS cryptographic library, as used
17068 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
17070 If you prefer more security and are willing to break some clients, raise this
17073 Note that the value passed to GnuTLS for *generating* a new prime may be a
17074 little less than this figure, because GnuTLS is inexact and may produce a
17075 larger prime than requested.
17078 .option tls_dhparam main string&!! unset
17079 .cindex "TLS" "D-H parameters for server"
17080 The value of this option is expanded and indicates the source of DH parameters
17081 to be used by Exim.
17083 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
17084 local DH parameters*&, which has been supported across all versions of Exim. The
17085 other specific constants available are a fallback so that even when
17086 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
17088 If &%tls_dhparam%& is a filename starting with a &`/`&,
17089 then it names a file from which DH
17090 parameters should be loaded. If the file exists, it should hold a PEM-encoded
17091 PKCS#3 representation of the DH prime. If the file does not exist, for
17092 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
17093 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
17094 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
17095 and treated as though the &%tls_dhparam%& were set to "none".
17097 If this option expands to the string "none", then no DH parameters will be
17100 If this option expands to the string "historic" and Exim is using GnuTLS, then
17101 Exim will attempt to load a file from inside the spool directory. If the file
17102 does not exist, Exim will attempt to create it.
17103 See section &<<SECTgnutlsparam>>& for further details.
17105 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
17106 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
17108 In older versions of Exim the default was the 2048 bit prime described in section
17109 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
17110 in IKE is assigned number 23.
17112 Otherwise, the option must expand to the name used by Exim for any of a number
17113 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
17114 sources. As names, Exim uses a standard specified name, else "ike" followed by
17115 the number used by IKE, or "default" which corresponds to
17116 &`exim.dev.20160529.3`&.
17118 The available standard primes are:
17119 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
17120 &`ike1`&, &`ike2`&, &`ike5`&,
17121 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
17122 &`ike22`&, &`ike23`& and &`ike24`&.
17124 The available additional primes are:
17125 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
17127 Some of these will be too small to be accepted by clients.
17128 Some may be too large to be accepted by clients.
17129 The open cryptographic community has suspicions about the integrity of some
17130 of the later IKE values, which led into RFC7919 providing new fixed constants
17131 (the "ffdhe" identifiers).
17133 At this point, all of the "ike" values should be considered obsolete;
17134 they're still in Exim to avoid breaking unusual configurations, but are
17135 candidates for removal the next time we have backwards-incompatible changes.
17137 The TLS protocol does not negotiate an acceptable size for this; clients tend
17138 to hard-drop connections if what is offered by the server is unacceptable,
17139 whether too large or too small, and there's no provision for the client to
17140 tell the server what these constraints are. Thus, as a server operator, you
17141 need to make an educated guess as to what is most likely to work for your
17144 Some known size constraints suggest that a bit-size in the range 2048 to 2236
17145 is most likely to maximise interoperability. The upper bound comes from
17146 applications using the Mozilla Network Security Services (NSS) library, which
17147 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
17148 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
17149 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
17150 acceptable bound from 1024 to 2048.
17153 .option tls_eccurve main string&!! &`auto`&
17154 .cindex TLS "EC cryptography"
17155 This option selects a EC curve for use by Exim when used with OpenSSL.
17156 It has no effect when Exim is used with GnuTLS.
17158 After expansion it must contain a valid EC curve parameter, such as
17159 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
17160 for valid selections.
17162 For OpenSSL versions before (and not including) 1.0.2, the string
17163 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
17164 &`auto`& tells the library to choose.
17166 If the option expands to an empty string, no EC curves will be enabled.
17169 .option tls_ocsp_file main string&!! unset
17170 .cindex TLS "certificate status"
17171 .cindex TLS "OCSP proof file"
17173 must if set expand to the absolute path to a file which contains a current
17174 status proof for the server's certificate, as obtained from the
17175 Certificate Authority.
17177 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
17180 .option tls_on_connect_ports main "string list" unset
17183 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
17184 operate the obsolete SSMTP (SMTPS) protocol, where a TLS session is immediately
17185 set up without waiting for the client to issue a STARTTLS command. For
17186 further details, see section &<<SECTsupobssmt>>&.
17190 .option tls_privatekey main string&!! unset
17191 .cindex "TLS" "server private key; location of"
17192 The value of this option is expanded, and must then be the absolute path to a
17193 file which contains the server's private key. If this option is unset, or if
17194 the expansion is forced to fail, or the result is an empty string, the private
17195 key is assumed to be in the same file as the server's certificates. See chapter
17196 &<<CHAPTLS>>& for further details.
17198 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17201 .option tls_remember_esmtp main boolean false
17202 .cindex "TLS" "esmtp state; remembering"
17203 .cindex "TLS" "broken clients"
17204 If this option is set true, Exim violates the RFCs by remembering that it is in
17205 &"esmtp"& state after successfully negotiating a TLS session. This provides
17206 support for broken clients that fail to send a new EHLO after starting a
17210 .option tls_require_ciphers main string&!! unset
17211 .cindex "TLS" "requiring specific ciphers"
17212 .cindex "cipher" "requiring specific"
17213 This option controls which ciphers can be used for incoming TLS connections.
17214 The &(smtp)& transport has an option of the same name for controlling outgoing
17215 connections. This option is expanded for each connection, so can be varied for
17216 different clients if required. The value of this option must be a list of
17217 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
17218 in somewhat different ways. If GnuTLS is being used, the client controls the
17219 preference order of the available ciphers. Details are given in sections
17220 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17223 .option tls_try_verify_hosts main "host list&!!" unset
17224 .cindex "TLS" "client certificate verification"
17225 .cindex "certificate" "verification of client"
17226 See &%tls_verify_hosts%& below.
17229 .option tls_verify_certificates main string&!! system
17230 .cindex "TLS" "client certificate verification"
17231 .cindex "certificate" "verification of client"
17232 The value of this option is expanded, and must then be either the
17234 or the absolute path to
17235 a file or directory containing permitted certificates for clients that
17236 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17238 The "system" value for the option will use a
17239 system default location compiled into the SSL library.
17240 This is not available for GnuTLS versions preceding 3.0.20,
17241 and will be taken as empty; an explicit location
17244 The use of a directory for the option value is not available for GnuTLS versions
17245 preceding 3.3.6 and a single file must be used.
17247 With OpenSSL the certificates specified
17249 either by file or directory
17250 are added to those given by the system default location.
17252 These certificates should be for the certificate authorities trusted, rather
17253 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17254 the value is a file then the certificates are sent by Exim as a server to
17255 connecting clients, defining the list of accepted certificate authorities.
17256 Thus the values defined should be considered public data. To avoid this,
17257 use the explicit directory version.
17259 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17261 A forced expansion failure or setting to an empty string is equivalent to
17265 .option tls_verify_hosts main "host list&!!" unset
17266 .cindex "TLS" "client certificate verification"
17267 .cindex "certificate" "verification of client"
17268 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17269 certificates from clients. The expected certificates are defined by
17270 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17271 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17272 &%tls_verify_certificates%& is not set.
17274 Any client that matches &%tls_verify_hosts%& is constrained by
17275 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17276 present one of the listed certificates. If it does not, the connection is
17277 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17278 the host to use TLS. It can still send SMTP commands through unencrypted
17279 connections. Forcing a client to use TLS has to be done separately using an
17280 ACL to reject inappropriate commands when the connection is not encrypted.
17282 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17283 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17284 certificate and checks it against &%tls_verify_certificates%&, but does not
17285 abort the connection if there is no certificate or if it does not match. This
17286 state can be detected in an ACL, which makes it possible to implement policies
17287 such as &"accept for relay only if a verified certificate has been received,
17288 but accept for local delivery if encrypted, even without a verified
17291 Client hosts that match neither of these lists are not asked to present
17295 .option trusted_groups main "string list&!!" unset
17296 .cindex "trusted groups"
17297 .cindex "groups" "trusted"
17298 This option is expanded just once, at the start of Exim's processing. If this
17299 option is set, any process that is running in one of the listed groups, or
17300 which has one of them as a supplementary group, is trusted. The groups can be
17301 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17302 details of what trusted callers are permitted to do. If neither
17303 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17306 .option trusted_users main "string list&!!" unset
17307 .cindex "trusted users"
17308 .cindex "user" "trusted"
17309 This option is expanded just once, at the start of Exim's processing. If this
17310 option is set, any process that is running as one of the listed users is
17311 trusted. The users can be specified numerically or by name. See section
17312 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17313 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17314 Exim user are trusted.
17316 .option unknown_login main string&!! unset
17317 .cindex "uid (user id)" "unknown caller"
17318 .vindex "&$caller_uid$&"
17319 This is a specialized feature for use in unusual configurations. By default, if
17320 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17321 gives up. The &%unknown_login%& option can be used to set a login name to be
17322 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17323 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17324 is used for the user's real name (gecos field), unless this has been set by the
17327 .option unknown_username main string unset
17328 See &%unknown_login%&.
17330 .option untrusted_set_sender main "address list&!!" unset
17331 .cindex "trusted users"
17332 .cindex "sender" "setting by untrusted user"
17333 .cindex "untrusted user setting sender"
17334 .cindex "user" "untrusted setting sender"
17335 .cindex "envelope sender"
17336 When an untrusted user submits a message to Exim using the standard input, Exim
17337 normally creates an envelope sender address from the user's login and the
17338 default qualification domain. Data from the &%-f%& option (for setting envelope
17339 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17340 is used) is ignored.
17342 However, untrusted users are permitted to set an empty envelope sender address,
17343 to declare that a message should never generate any bounces. For example:
17345 exim -f '<>' user@domain.example
17347 .vindex "&$sender_ident$&"
17348 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17349 other envelope sender addresses in a controlled way. When it is set, untrusted
17350 users are allowed to set envelope sender addresses that match any of the
17351 patterns in the list. Like all address lists, the string is expanded. The
17352 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17353 users to setting senders that start with their login ids
17354 followed by a hyphen
17355 by a setting like this:
17357 untrusted_set_sender = ^$sender_ident-
17359 If you want to allow untrusted users to set envelope sender addresses without
17360 restriction, you can use
17362 untrusted_set_sender = *
17364 The &%untrusted_set_sender%& option applies to all forms of local input, but
17365 only to the setting of the envelope sender. It does not permit untrusted users
17366 to use the other options which trusted user can use to override message
17367 parameters. Furthermore, it does not stop Exim from removing an existing
17368 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17369 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17370 overriding these actions. The handling of the &'Sender:'& header is also
17371 described in section &<<SECTthesenhea>>&.
17373 The log line for a message's arrival shows the envelope sender following
17374 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17375 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17376 envelope sender address, the user's login is shown in parentheses after the
17380 .option uucp_from_pattern main string "see below"
17381 .cindex "&""From""& line"
17382 .cindex "UUCP" "&""From""& line"
17383 Some applications that pass messages to an MTA via a command line interface use
17384 an initial line starting with &"From&~"& to pass the envelope sender. In
17385 particular, this is used by UUCP software. Exim recognizes such a line by means
17386 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17387 matches, the sender address is constructed by expanding the contents of
17388 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17389 default pattern recognizes lines in the following two forms:
17391 From ph10 Fri Jan 5 12:35 GMT 1996
17392 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17394 The pattern can be seen by running
17396 exim -bP uucp_from_pattern
17398 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17399 year in the second case. The first word after &"From&~"& is matched in the
17400 regular expression by a parenthesized subpattern. The default value for
17401 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17402 (&"ph10"& in the example above) as the message's sender. See also
17403 &%ignore_fromline_hosts%&.
17406 .option uucp_from_sender main string&!! &`$1`&
17407 See &%uucp_from_pattern%& above.
17410 .option warn_message_file main string unset
17411 .cindex "warning of delay" "customizing the message"
17412 .cindex "customizing" "warning message"
17413 This option defines a template file containing paragraphs of text to be used
17414 for constructing the warning message which is sent by Exim when a message has
17415 been on the queue for a specified amount of time, as specified by
17416 &%delay_warning%&. Details of the file's contents are given in chapter
17417 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17420 .option write_rejectlog main boolean true
17421 .cindex "reject log" "disabling"
17422 If this option is set false, Exim no longer writes anything to the reject log.
17423 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17424 .ecindex IIDconfima
17425 .ecindex IIDmaiconf
17430 . ////////////////////////////////////////////////////////////////////////////
17431 . ////////////////////////////////////////////////////////////////////////////
17433 .chapter "Generic options for routers" "CHAProutergeneric"
17434 .scindex IIDgenoprou1 "options" "generic; for routers"
17435 .scindex IIDgenoprou2 "generic options" "router"
17436 This chapter describes the generic options that apply to all routers.
17437 Those that are preconditions are marked with ‡ in the &"use"& field.
17439 For a general description of how a router operates, see sections
17440 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17441 which the preconditions are tested. The order of expansion of the options that
17442 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17443 &%headers_remove%&, &%transport%&.
17447 .option address_data routers string&!! unset
17448 .cindex "router" "data attached to address"
17449 The string is expanded just before the router is run, that is, after all the
17450 precondition tests have succeeded. If the expansion is forced to fail, the
17451 router declines, the value of &%address_data%& remains unchanged, and the
17452 &%more%& option controls what happens next. Other expansion failures cause
17453 delivery of the address to be deferred.
17455 .vindex "&$address_data$&"
17456 When the expansion succeeds, the value is retained with the address, and can be
17457 accessed using the variable &$address_data$& in the current router, subsequent
17458 routers, and the eventual transport.
17460 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17461 that runs a user's filter file, the contents of &$address_data$& are accessible
17462 in the filter. This is not normally a problem, because such data is usually
17463 either not confidential or it &"belongs"& to the current user, but if you do
17464 put confidential data into &$address_data$& you need to remember this point.
17466 Even if the router declines or passes, the value of &$address_data$& remains
17467 with the address, though it can be changed by another &%address_data%& setting
17468 on a subsequent router. If a router generates child addresses, the value of
17469 &$address_data$& propagates to them. This also applies to the special kind of
17470 &"child"& that is generated by a router with the &%unseen%& option.
17472 The idea of &%address_data%& is that you can use it to look up a lot of data
17473 for the address once, and then pick out parts of the data later. For example,
17474 you could use a single LDAP lookup to return a string of the form
17476 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17478 In the transport you could pick out the mailbox by a setting such as
17480 file = ${extract{mailbox}{$address_data}}
17482 This makes the configuration file less messy, and also reduces the number of
17483 lookups (though Exim does cache lookups).
17485 .vindex "&$sender_address_data$&"
17486 .vindex "&$address_data$&"
17487 The &%address_data%& facility is also useful as a means of passing information
17488 from one router to another, and from a router to a transport. In addition, if
17489 &$address_data$& is set by a router when verifying a recipient address from an
17490 ACL, it remains available for use in the rest of the ACL statement. After
17491 verifying a sender, the value is transferred to &$sender_address_data$&.
17495 .option address_test routers&!? boolean true
17497 .cindex "router" "skipping when address testing"
17498 If this option is set false, the router is skipped when routing is being tested
17499 by means of the &%-bt%& command line option. This can be a convenience when
17500 your first router sends messages to an external scanner, because it saves you
17501 having to set the &"already scanned"& indicator when testing real address
17506 .option cannot_route_message routers string&!! unset
17507 .cindex "router" "customizing &""cannot route""& message"
17508 .cindex "customizing" "&""cannot route""& message"
17509 This option specifies a text message that is used when an address cannot be
17510 routed because Exim has run out of routers. The default message is
17511 &"Unrouteable address"&. This option is useful only on routers that have
17512 &%more%& set false, or on the very last router in a configuration, because the
17513 value that is used is taken from the last router that is considered. This
17514 includes a router that is skipped because its preconditions are not met, as
17515 well as a router that declines. For example, using the default configuration,
17518 cannot_route_message = Remote domain not found in DNS
17520 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17523 cannot_route_message = Unknown local user
17525 on the final router that checks for local users. If string expansion fails for
17526 this option, the default message is used. Unless the expansion failure was
17527 explicitly forced, a message about the failure is written to the main and panic
17528 logs, in addition to the normal message about the routing failure.
17531 .option caseful_local_part routers boolean false
17532 .cindex "case of local parts"
17533 .cindex "router" "case of local parts"
17534 By default, routers handle the local parts of addresses in a case-insensitive
17535 manner, though the actual case is preserved for transmission with the message.
17536 If you want the case of letters to be significant in a router, you must set
17537 this option true. For individual router options that contain address or local
17538 part lists (for example, &%local_parts%&), case-sensitive matching can be
17539 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17542 .vindex "&$local_part$&"
17543 .vindex "&$original_local_part$&"
17544 .vindex "&$parent_local_part$&"
17545 The value of the &$local_part$& variable is forced to lower case while a
17546 router is running unless &%caseful_local_part%& is set. When a router assigns
17547 an address to a transport, the value of &$local_part$& when the transport runs
17548 is the same as it was in the router. Similarly, when a router generates child
17549 addresses by aliasing or forwarding, the values of &$original_local_part$&
17550 and &$parent_local_part$& are those that were used by the redirecting router.
17552 This option applies to the processing of an address by a router. When a
17553 recipient address is being processed in an ACL, there is a separate &%control%&
17554 modifier that can be used to specify case-sensitive processing within the ACL
17555 (see section &<<SECTcontrols>>&).
17559 .option check_local_user routers&!? boolean false
17560 .cindex "local user, checking in router"
17561 .cindex "router" "checking for local user"
17562 .cindex "&_/etc/passwd_&"
17564 When this option is true, Exim checks that the local part of the recipient
17565 address (with affixes removed if relevant) is the name of an account on the
17566 local system. The check is done by calling the &[getpwnam()]& function rather
17567 than trying to read &_/etc/passwd_& directly. This means that other methods of
17568 holding password data (such as NIS) are supported. If the local part is a local
17569 user, &$home$& is set from the password data, and can be tested in other
17570 preconditions that are evaluated after this one (the order of evaluation is
17571 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17572 overridden by &%router_home_directory%&. If the local part is not a local user,
17573 the router is skipped.
17575 If you want to check that the local part is either the name of a local user
17576 or matches something else, you cannot combine &%check_local_user%& with a
17577 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17578 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17579 setting to achieve this. For example:
17581 local_parts = passwd;$local_part : lsearch;/etc/other/users
17583 Note, however, that the side effects of &%check_local_user%& (such as setting
17584 up a home directory) do not occur when a &(passwd)& lookup is used in a
17585 &%local_parts%& (or any other) precondition.
17589 .option condition routers&!? string&!! unset
17590 .cindex "router" "customized precondition"
17591 This option specifies a general precondition test that has to succeed for the
17592 router to be called. The &%condition%& option is the last precondition to be
17593 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17594 result is a forced failure, or an empty string, or one of the strings &"0"& or
17595 &"no"& or &"false"& (checked without regard to the case of the letters), the
17596 router is skipped, and the address is offered to the next one.
17598 If the result is any other value, the router is run (as this is the last
17599 precondition to be evaluated, all the other preconditions must be true).
17601 This option is unusual in that multiple &%condition%& options may be present.
17602 All &%condition%& options must succeed.
17604 The &%condition%& option provides a means of applying custom conditions to the
17605 running of routers. Note that in the case of a simple conditional expansion,
17606 the default expansion values are exactly what is wanted. For example:
17608 condition = ${if >{$message_age}{600}}
17610 Because of the default behaviour of the string expansion, this is equivalent to
17612 condition = ${if >{$message_age}{600}{true}{}}
17615 A multiple condition example, which succeeds:
17617 condition = ${if >{$message_age}{600}}
17618 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17622 If the expansion fails (other than forced failure) delivery is deferred. Some
17623 of the other precondition options are common special cases that could in fact
17624 be specified using &%condition%&.
17626 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17627 are far older, and use one set of semantics. ACLs are newer and when
17628 they were created, the ACL &%condition%& process was given far stricter
17629 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17630 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17631 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17632 Router rules processing behavior.
17634 This is best illustrated in an example:
17636 # If used in an ACL condition will fail with a syntax error, but
17637 # in a router condition any extra characters are treated as a string
17639 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17642 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17645 In each example above, the &%if%& statement actually ends after
17646 &"{google.com}}"&. Since no true or false braces were defined, the
17647 default &%if%& behavior is to return a boolean true or a null answer
17648 (which evaluates to false). The rest of the line is then treated as a
17649 string. So the first example resulted in the boolean answer &"true"&
17650 with the string &" {yes} {no}}"& appended to it. The second example
17651 resulted in the null output (indicating false) with the string
17652 &" {yes} {no}}"& appended to it.
17654 In fact you can put excess forward braces in too. In the router
17655 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17656 mean something, like after a &"$"& or when required as part of a
17657 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17660 Thus, in a Router, the above expansion strings will both always evaluate
17661 true, as the result of expansion is a non-empty string which doesn't
17662 match an explicit false value. This can be tricky to debug. By
17663 contrast, in an ACL either of those strings will always result in an
17664 expansion error because the result doesn't look sufficiently boolean.
17667 .option debug_print routers string&!! unset
17668 .cindex "testing" "variables in drivers"
17669 If this option is set and debugging is enabled (see the &%-d%& command line
17670 option) or in address-testing mode (see the &%-bt%& command line option),
17671 the string is expanded and included in the debugging output.
17672 If expansion of the string fails, the error message is written to the debugging
17673 output, and Exim carries on processing.
17674 This option is provided to help with checking out the values of variables and
17675 so on when debugging router configurations. For example, if a &%condition%&
17676 option appears not to be working, &%debug_print%& can be used to output the
17677 variables it references. The output happens after checks for &%domains%&,
17678 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17679 are tested. A newline is added to the text if it does not end with one.
17680 The variable &$router_name$& contains the name of the router.
17684 .option disable_logging routers boolean false
17685 If this option is set true, nothing is logged for any routing errors
17686 or for any deliveries caused by this router. You should not set this option
17687 unless you really, really know what you are doing. See also the generic
17688 transport option of the same name.
17690 .option dnssec_request_domains routers "domain list&!!" unset
17691 .cindex "MX record" "security"
17692 .cindex "DNSSEC" "MX lookup"
17693 .cindex "security" "MX lookup"
17694 .cindex "DNS" "DNSSEC"
17695 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17696 the dnssec request bit set.
17697 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17699 .option dnssec_require_domains routers "domain list&!!" unset
17700 .cindex "MX record" "security"
17701 .cindex "DNSSEC" "MX lookup"
17702 .cindex "security" "MX lookup"
17703 .cindex "DNS" "DNSSEC"
17704 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
17705 the dnssec request bit set. Any returns not having the Authenticated Data bit
17706 (AD bit) set will be ignored and logged as a host-lookup failure.
17707 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17710 .option domains routers&!? "domain list&!!" unset
17711 .cindex "router" "restricting to specific domains"
17712 .vindex "&$domain_data$&"
17713 If this option is set, the router is skipped unless the current domain matches
17714 the list. If the match is achieved by means of a file lookup, the data that the
17715 lookup returned for the domain is placed in &$domain_data$& for use in string
17716 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17717 a list of the order in which preconditions are evaluated.
17721 .option driver routers string unset
17722 This option must always be set. It specifies which of the available routers is
17726 .option dsn_lasthop routers boolean false
17727 .cindex "DSN" "success"
17728 .cindex "Delivery Status Notification" "success"
17729 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17730 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17731 instead send a success DSN as if the next hop does not support DSN.
17732 Not effective on redirect routers.
17736 .option errors_to routers string&!! unset
17737 .cindex "envelope sender"
17738 .cindex "router" "changing address for errors"
17739 If a router successfully handles an address, it may assign the address to a
17740 transport for delivery or it may generate child addresses. In both cases, if
17741 there is a delivery problem during later processing, the resulting bounce
17742 message is sent to the address that results from expanding this string,
17743 provided that the address verifies successfully. The &%errors_to%& option is
17744 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17746 The &%errors_to%& setting associated with an address can be overridden if it
17747 subsequently passes through other routers that have their own &%errors_to%&
17748 settings, or if the message is delivered by a transport with a &%return_path%&
17751 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17752 the expansion fails to verify, the errors address associated with the incoming
17753 address is used. At top level, this is the envelope sender. A non-forced
17754 expansion failure causes delivery to be deferred.
17756 If an address for which &%errors_to%& has been set ends up being delivered over
17757 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17758 any bounces that are generated by other MTAs on the delivery route are also
17759 sent there. You can set &%errors_to%& to the empty string by either of these
17765 An expansion item that yields an empty string has the same effect. If you do
17766 this, a locally detected delivery error for addresses processed by this router
17767 no longer gives rise to a bounce message; the error is discarded. If the
17768 address is delivered to a remote host, the return path is set to &`<>`&, unless
17769 overridden by the &%return_path%& option on the transport.
17771 .vindex "&$address_data$&"
17772 If for some reason you want to discard local errors, but use a non-empty
17773 MAIL command for remote delivery, you can preserve the original return
17774 path in &$address_data$& in the router, and reinstate it in the transport by
17775 setting &%return_path%&.
17777 The most common use of &%errors_to%& is to direct mailing list bounces to the
17778 manager of the list, as described in section &<<SECTmailinglists>>&, or to
17779 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
17783 .option expn routers&!? boolean true
17784 .cindex "address" "testing"
17785 .cindex "testing" "addresses"
17786 .cindex "EXPN" "router skipping"
17787 .cindex "router" "skipping for EXPN"
17788 If this option is turned off, the router is skipped when testing an address
17789 as a result of processing an SMTP EXPN command. You might, for example,
17790 want to turn it off on a router for users' &_.forward_& files, while leaving it
17791 on for the system alias file.
17792 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
17795 The use of the SMTP EXPN command is controlled by an ACL (see chapter
17796 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
17797 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
17801 .option fail_verify routers boolean false
17802 .cindex "router" "forcing verification failure"
17803 Setting this option has the effect of setting both &%fail_verify_sender%& and
17804 &%fail_verify_recipient%& to the same value.
17808 .option fail_verify_recipient routers boolean false
17809 If this option is true and an address is accepted by this router when
17810 verifying a recipient, verification fails.
17814 .option fail_verify_sender routers boolean false
17815 If this option is true and an address is accepted by this router when
17816 verifying a sender, verification fails.
17820 .option fallback_hosts routers "string list" unset
17821 .cindex "router" "fallback hosts"
17822 .cindex "fallback" "hosts specified on router"
17823 String expansion is not applied to this option. The argument must be a
17824 colon-separated list of host names or IP addresses. The list separator can be
17825 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
17826 each name or address. In fact, the format of each item is exactly the same as
17827 defined for the list of hosts in a &(manualroute)& router (see section
17828 &<<SECTformatonehostitem>>&).
17830 If a router queues an address for a remote transport, this host list is
17831 associated with the address, and used instead of the transport's fallback host
17832 list. If &%hosts_randomize%& is set on the transport, the order of the list is
17833 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
17834 transport for further details.
17837 .option group routers string&!! "see below"
17838 .cindex "gid (group id)" "local delivery"
17839 .cindex "local transports" "uid and gid"
17840 .cindex "transport" "local"
17841 .cindex "router" "setting group"
17842 When a router queues an address for a transport, and the transport does not
17843 specify a group, the group given here is used when running the delivery
17845 The group may be specified numerically or by name. If expansion fails, the
17846 error is logged and delivery is deferred.
17847 The default is unset, unless &%check_local_user%& is set, when the default
17848 is taken from the password information. See also &%initgroups%& and &%user%&
17849 and the discussion in chapter &<<CHAPenvironment>>&.
17853 .option headers_add routers list&!! unset
17854 .cindex "header lines" "adding"
17855 .cindex "router" "adding header lines"
17856 This option specifies a list of text headers,
17857 newline-separated (by default, changeable in the usual way),
17858 that is associated with any addresses that are accepted by the router.
17859 Each item is separately expanded, at routing time. However, this
17860 option has no effect when an address is just being verified. The way in which
17861 the text is used to add header lines at transport time is described in section
17862 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
17863 message is in the process of being transported. This means that references to
17864 header lines in string expansions in the transport's configuration do not
17865 &"see"& the added header lines.
17867 The &%headers_add%& option is expanded after &%errors_to%&, but before
17868 &%headers_remove%& and &%transport%&. If an item is empty, or if
17869 an item expansion is forced to fail, the item has no effect. Other expansion
17870 failures are treated as configuration errors.
17872 Unlike most options, &%headers_add%& can be specified multiple times
17873 for a router; all listed headers are added.
17875 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
17876 router that has the &%one_time%& option set.
17878 .cindex "duplicate addresses"
17879 .oindex "&%unseen%&"
17880 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17881 additions are deleted when the address is passed on to subsequent routers.
17882 For a &%redirect%& router, if a generated address is the same as the incoming
17883 address, this can lead to duplicate addresses with different header
17884 modifications. Exim does not do duplicate deliveries (except, in certain
17885 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
17886 which of the duplicates is discarded, so this ambiguous situation should be
17887 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
17891 .option headers_remove routers list&!! unset
17892 .cindex "header lines" "removing"
17893 .cindex "router" "removing header lines"
17894 This option specifies a list of text headers,
17895 colon-separated (by default, changeable in the usual way),
17896 that is associated with any addresses that are accepted by the router.
17897 Each item is separately expanded, at routing time. However, this
17898 option has no effect when an address is just being verified. The way in which
17899 the text is used to remove header lines at transport time is described in
17900 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
17901 the message is in the process of being transported. This means that references
17902 to header lines in string expansions in the transport's configuration still
17903 &"see"& the original header lines.
17905 The &%headers_remove%& option is expanded after &%errors_to%& and
17906 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
17907 the item has no effect. Other expansion failures are treated as configuration
17910 Unlike most options, &%headers_remove%& can be specified multiple times
17911 for a router; all listed headers are removed.
17913 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
17914 router that has the &%one_time%& option set.
17916 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
17917 removal requests are deleted when the address is passed on to subsequent
17918 routers, and this can lead to problems with duplicates -- see the similar
17919 warning for &%headers_add%& above.
17921 &*Warning 3*&: Because of the separate expansion of the list items,
17922 items that contain a list separator must have it doubled.
17923 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
17927 .option ignore_target_hosts routers "host list&!!" unset
17928 .cindex "IP address" "discarding"
17929 .cindex "router" "discarding IP addresses"
17930 Although this option is a host list, it should normally contain IP address
17931 entries rather than names. If any host that is looked up by the router has an
17932 IP address that matches an item in this list, Exim behaves as if that IP
17933 address did not exist. This option allows you to cope with rogue DNS entries
17936 remote.domain.example. A 127.0.0.1
17940 ignore_target_hosts = 127.0.0.1
17942 on the relevant router. If all the hosts found by a &(dnslookup)& router are
17943 discarded in this way, the router declines. In a conventional configuration, an
17944 attempt to mail to such a domain would normally provoke the &"unrouteable
17945 domain"& error, and an attempt to verify an address in the domain would fail.
17946 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
17947 router declines if presented with one of the listed addresses.
17949 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
17950 means of the first or the second of the following settings, respectively:
17952 ignore_target_hosts = 0.0.0.0/0
17953 ignore_target_hosts = <; 0::0/0
17955 The pattern in the first line matches all IPv4 addresses, whereas the pattern
17956 in the second line matches all IPv6 addresses.
17958 This option may also be useful for ignoring link-local and site-local IPv6
17959 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
17960 is expanded before use as a list, it is possible to make it dependent on the
17961 domain that is being routed.
17963 .vindex "&$host_address$&"
17964 During its expansion, &$host_address$& is set to the IP address that is being
17967 .option initgroups routers boolean false
17968 .cindex "additional groups"
17969 .cindex "groups" "additional"
17970 .cindex "local transports" "uid and gid"
17971 .cindex "transport" "local"
17972 If the router queues an address for a transport, and this option is true, and
17973 the uid supplied by the router is not overridden by the transport, the
17974 &[initgroups()]& function is called when running the transport to ensure that
17975 any additional groups associated with the uid are set up. See also &%group%&
17976 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
17980 .option local_part_prefix routers&!? "string list" unset
17981 .cindex "router" "prefix for local part"
17982 .cindex "prefix" "for local part, used in router"
17983 If this option is set, the router is skipped unless the local part starts with
17984 one of the given strings, or &%local_part_prefix_optional%& is true. See
17985 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
17988 The list is scanned from left to right, and the first prefix that matches is
17989 used. A limited form of wildcard is available; if the prefix begins with an
17990 asterisk, it matches the longest possible sequence of arbitrary characters at
17991 the start of the local part. An asterisk should therefore always be followed by
17992 some character that does not occur in normal local parts.
17993 .cindex "multiple mailboxes"
17994 .cindex "mailbox" "multiple"
17995 Wildcarding can be used to set up multiple user mailboxes, as described in
17996 section &<<SECTmulbox>>&.
17998 .vindex "&$local_part$&"
17999 .vindex "&$local_part_prefix$&"
18000 During the testing of the &%local_parts%& option, and while the router is
18001 running, the prefix is removed from the local part, and is available in the
18002 expansion variable &$local_part_prefix$&. When a message is being delivered, if
18003 the router accepts the address, this remains true during subsequent delivery by
18004 a transport. In particular, the local part that is transmitted in the RCPT
18005 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
18006 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
18007 the relevant transport.
18009 When an address is being verified, &%local_part_prefix%& affects only the
18010 behaviour of the router. If the callout feature of verification is in use, this
18011 means that the full address, including the prefix, will be used during the
18014 The prefix facility is commonly used to handle local parts of the form
18015 &%owner-something%&. Another common use is to support local parts of the form
18016 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
18017 to tell a user their forwarding is broken &-- by placing a router like this one
18018 immediately before the router that handles &_.forward_& files:
18022 local_part_prefix = real-
18024 transport = local_delivery
18026 For security, it would probably be a good idea to restrict the use of this
18027 router to locally-generated messages, using a condition such as this:
18029 condition = ${if match {$sender_host_address}\
18030 {\N^(|127\.0\.0\.1)$\N}}
18033 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
18034 both conditions must be met if not optional. Care must be taken if wildcards
18035 are used in both a prefix and a suffix on the same router. Different
18036 separator characters must be used to avoid ambiguity.
18039 .option local_part_prefix_optional routers boolean false
18040 See &%local_part_prefix%& above.
18044 .option local_part_suffix routers&!? "string list" unset
18045 .cindex "router" "suffix for local part"
18046 .cindex "suffix for local part" "used in router"
18047 This option operates in the same way as &%local_part_prefix%&, except that the
18048 local part must end (rather than start) with the given string, the
18049 &%local_part_suffix_optional%& option determines whether the suffix is
18050 mandatory, and the wildcard * character, if present, must be the last
18051 character of the suffix. This option facility is commonly used to handle local
18052 parts of the form &%something-request%& and multiple user mailboxes of the form
18056 .option local_part_suffix_optional routers boolean false
18057 See &%local_part_suffix%& above.
18061 .option local_parts routers&!? "local part list&!!" unset
18062 .cindex "router" "restricting to specific local parts"
18063 .cindex "local part" "checking in router"
18064 The router is run only if the local part of the address matches the list.
18065 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18067 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
18068 string is expanded, it is possible to make it depend on the domain, for
18071 local_parts = dbm;/usr/local/specials/$domain
18073 .vindex "&$local_part_data$&"
18074 If the match is achieved by a lookup, the data that the lookup returned
18075 for the local part is placed in the variable &$local_part_data$& for use in
18076 expansions of the router's private options. You might use this option, for
18077 example, if you have a large number of local virtual domains, and you want to
18078 send all postmaster mail to the same place without having to set up an alias in
18079 each virtual domain:
18083 local_parts = postmaster
18084 data = postmaster@real.domain.example
18088 .option log_as_local routers boolean "see below"
18089 .cindex "log" "delivery line"
18090 .cindex "delivery" "log line format"
18091 Exim has two logging styles for delivery, the idea being to make local
18092 deliveries stand out more visibly from remote ones. In the &"local"& style, the
18093 recipient address is given just as the local part, without a domain. The use of
18094 this style is controlled by this option. It defaults to true for the &(accept)&
18095 router, and false for all the others. This option applies only when a
18096 router assigns an address to a transport. It has no effect on routers that
18097 redirect addresses.
18101 .option more routers boolean&!! true
18102 The result of string expansion for this option must be a valid boolean value,
18103 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18104 result causes an error, and delivery is deferred. If the expansion is forced to
18105 fail, the default value for the option (true) is used. Other failures cause
18106 delivery to be deferred.
18108 If this option is set false, and the router declines to handle the address, no
18109 further routers are tried, routing fails, and the address is bounced.
18111 However, if the router explicitly passes an address to the following router by
18112 means of the setting
18116 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
18117 does not affect the behaviour if one of the precondition tests fails. In that
18118 case, the address is always passed to the next router.
18120 Note that &%address_data%& is not considered to be a precondition. If its
18121 expansion is forced to fail, the router declines, and the value of &%more%&
18122 controls what happens next.
18125 .option pass_on_timeout routers boolean false
18126 .cindex "timeout" "of router"
18127 .cindex "router" "timeout"
18128 If a router times out during a host lookup, it normally causes deferral of the
18129 address. If &%pass_on_timeout%& is set, the address is passed on to the next
18130 router, overriding &%no_more%&. This may be helpful for systems that are
18131 intermittently connected to the Internet, or those that want to pass to a smart
18132 host any messages that cannot immediately be delivered.
18134 There are occasional other temporary errors that can occur while doing DNS
18135 lookups. They are treated in the same way as a timeout, and this option
18136 applies to all of them.
18140 .option pass_router routers string unset
18141 .cindex "router" "go to after &""pass""&"
18142 Routers that recognize the generic &%self%& option (&(dnslookup)&,
18143 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
18144 routing to continue, and overriding a false setting of &%more%&. When one of
18145 these routers returns &"pass"&, the address is normally handed on to the next
18146 router in sequence. This can be changed by setting &%pass_router%& to the name
18147 of another router. However (unlike &%redirect_router%&) the named router must
18148 be below the current router, to avoid loops. Note that this option applies only
18149 to the special case of &"pass"&. It does not apply when a router returns
18150 &"decline"& because it cannot handle an address.
18154 .option redirect_router routers string unset
18155 .cindex "router" "start at after redirection"
18156 Sometimes an administrator knows that it is pointless to reprocess addresses
18157 generated from alias or forward files with the same router again. For
18158 example, if an alias file translates real names into login ids there is no
18159 point searching the alias file a second time, especially if it is a large file.
18161 The &%redirect_router%& option can be set to the name of any router instance.
18162 It causes the routing of any generated addresses to start at the named router
18163 instead of at the first router. This option has no effect if the router in
18164 which it is set does not generate new addresses.
18168 .option require_files routers&!? "string list&!!" unset
18169 .cindex "file" "requiring for router"
18170 .cindex "router" "requiring file existence"
18171 This option provides a general mechanism for predicating the running of a
18172 router on the existence or non-existence of certain files or directories.
18173 Before running a router, as one of its precondition tests, Exim works its way
18174 through the &%require_files%& list, expanding each item separately.
18176 Because the list is split before expansion, any colons in expansion items must
18177 be doubled, or the facility for using a different list separator must be used.
18178 If any expansion is forced to fail, the item is ignored. Other expansion
18179 failures cause routing of the address to be deferred.
18181 If any expanded string is empty, it is ignored. Otherwise, except as described
18182 below, each string must be a fully qualified file path, optionally preceded by
18183 &"!"&. The paths are passed to the &[stat()]& function to test for the
18184 existence of the files or directories. The router is skipped if any paths not
18185 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
18188 If &[stat()]& cannot determine whether a file exists or not, delivery of
18189 the message is deferred. This can happen when NFS-mounted filesystems are
18192 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
18193 options, so you cannot use it to check for the existence of a file in which to
18194 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
18195 full list of the order in which preconditions are evaluated.) However, as
18196 these options are all expanded, you can use the &%exists%& expansion condition
18197 to make such tests. The &%require_files%& option is intended for checking files
18198 that the router may be going to use internally, or which are needed by a
18199 transport (for example &_.procmailrc_&).
18201 During delivery, the &[stat()]& function is run as root, but there is a
18202 facility for some checking of the accessibility of a file by another user.
18203 This is not a proper permissions check, but just a &"rough"& check that
18204 operates as follows:
18206 If an item in a &%require_files%& list does not contain any forward slash
18207 characters, it is taken to be the user (and optional group, separated by a
18208 comma) to be checked for subsequent files in the list. If no group is specified
18209 but the user is specified symbolically, the gid associated with the uid is
18212 require_files = mail:/some/file
18213 require_files = $local_part:$home/.procmailrc
18215 If a user or group name in a &%require_files%& list does not exist, the
18216 &%require_files%& condition fails.
18218 Exim performs the check by scanning along the components of the file path, and
18219 checking the access for the given uid and gid. It checks for &"x"& access on
18220 directories, and &"r"& access on the final file. Note that this means that file
18221 access control lists, if the operating system has them, are ignored.
18223 &*Warning 1*&: When the router is being run to verify addresses for an
18224 incoming SMTP message, Exim is not running as root, but under its own uid. This
18225 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18226 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18227 user is not permitted to read one of the directories on the file's path.
18229 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18230 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18231 without root access. In this case, if a check for access by a particular user
18232 is requested, Exim creates a subprocess that runs as that user, and tries the
18233 check again in that process.
18235 The default action for handling an unresolved EACCES is to consider it to
18236 be caused by a configuration error, and routing is deferred because the
18237 existence or non-existence of the file cannot be determined. However, in some
18238 circumstances it may be desirable to treat this condition as if the file did
18239 not exist. If the file name (or the exclamation mark that precedes the file
18240 name for non-existence) is preceded by a plus sign, the EACCES error is treated
18241 as if the file did not exist. For example:
18243 require_files = +/some/file
18245 If the router is not an essential part of verification (for example, it
18246 handles users' &_.forward_& files), another solution is to set the &%verify%&
18247 option false so that the router is skipped when verifying.
18251 .option retry_use_local_part routers boolean "see below"
18252 .cindex "hints database" "retry keys"
18253 .cindex "local part" "in retry keys"
18254 When a delivery suffers a temporary routing failure, a retry record is created
18255 in Exim's hints database. For addresses whose routing depends only on the
18256 domain, the key for the retry record should not involve the local part, but for
18257 other addresses, both the domain and the local part should be included.
18258 Usually, remote routing is of the former kind, and local routing is of the
18261 This option controls whether the local part is used to form the key for retry
18262 hints for addresses that suffer temporary errors while being handled by this
18263 router. The default value is true for any router that has &%check_local_user%&
18264 set, and false otherwise. Note that this option does not apply to hints keys
18265 for transport delays; they are controlled by a generic transport option of the
18268 The setting of &%retry_use_local_part%& applies only to the router on which it
18269 appears. If the router generates child addresses, they are routed
18270 independently; this setting does not become attached to them.
18274 .option router_home_directory routers string&!! unset
18275 .cindex "router" "home directory for"
18276 .cindex "home directory" "for router"
18278 This option sets a home directory for use while the router is running. (Compare
18279 &%transport_home_directory%&, which sets a home directory for later
18280 transporting.) In particular, if used on a &(redirect)& router, this option
18281 sets a value for &$home$& while a filter is running. The value is expanded;
18282 forced expansion failure causes the option to be ignored &-- other failures
18283 cause the router to defer.
18285 Expansion of &%router_home_directory%& happens immediately after the
18286 &%check_local_user%& test (if configured), before any further expansions take
18288 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18290 While the router is running, &%router_home_directory%& overrides the value of
18291 &$home$& that came from &%check_local_user%&.
18293 When a router accepts an address and assigns it to a local transport (including
18294 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18295 delivery), the home directory setting for the transport is taken from the first
18296 of these values that is set:
18299 The &%home_directory%& option on the transport;
18301 The &%transport_home_directory%& option on the router;
18303 The password data if &%check_local_user%& is set on the router;
18305 The &%router_home_directory%& option on the router.
18308 In other words, &%router_home_directory%& overrides the password data for the
18309 router, but not for the transport.
18313 .option self routers string freeze
18314 .cindex "MX record" "pointing to local host"
18315 .cindex "local host" "MX pointing to"
18316 This option applies to those routers that use a recipient address to find a
18317 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18318 and &(manualroute)& routers.
18319 Certain configurations of the &(queryprogram)& router can also specify a list
18321 Usually such routers are configured to send the message to a remote host via an
18322 &(smtp)& transport. The &%self%& option specifies what happens when the first
18323 host on the list turns out to be the local host.
18324 The way in which Exim checks for the local host is described in section
18325 &<<SECTreclocipadd>>&.
18327 Normally this situation indicates either an error in Exim's configuration (for
18328 example, the router should be configured not to process this domain), or an
18329 error in the DNS (for example, the MX should not point to this host). For this
18330 reason, the default action is to log the incident, defer the address, and
18331 freeze the message. The following alternatives are provided for use in special
18336 Delivery of the message is tried again later, but the message is not frozen.
18338 .vitem "&%reroute%&: <&'domain'&>"
18339 The domain is changed to the given domain, and the address is passed back to
18340 be reprocessed by the routers. No rewriting of headers takes place. This
18341 behaviour is essentially a redirection.
18343 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18344 The domain is changed to the given domain, and the address is passed back to be
18345 reprocessed by the routers. Any headers that contain the original domain are
18350 .vindex "&$self_hostname$&"
18351 The router passes the address to the next router, or to the router named in the
18352 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18353 subsequent routing and delivery, the variable &$self_hostname$& contains the
18354 name of the local host that the router encountered. This can be used to
18355 distinguish between different cases for hosts with multiple names. The
18361 ensures that only those addresses that routed to the local host are passed on.
18362 Without &%no_more%&, addresses that were declined for other reasons would also
18363 be passed to the next router.
18366 Delivery fails and an error report is generated.
18369 .cindex "local host" "sending to"
18370 The anomaly is ignored and the address is queued for the transport. This
18371 setting should be used with extreme caution. For an &(smtp)& transport, it
18372 makes sense only in cases where the program that is listening on the SMTP port
18373 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18374 different configuration file that handles the domain in another way.
18379 .option senders routers&!? "address list&!!" unset
18380 .cindex "router" "checking senders"
18381 If this option is set, the router is skipped unless the message's sender
18382 address matches something on the list.
18383 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18386 There are issues concerning verification when the running of routers is
18387 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18388 setting, it sets the sender to the null string. When using the &%-bt%& option
18389 to check a configuration file, it is necessary also to use the &%-f%& option to
18390 set an appropriate sender. For incoming mail, the sender is unset when
18391 verifying the sender, but is available when verifying any recipients. If the
18392 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18396 .option translate_ip_address routers string&!! unset
18397 .cindex "IP address" "translating"
18398 .cindex "packet radio"
18399 .cindex "router" "IP address translation"
18400 There exist some rare networking situations (for example, packet radio) where
18401 it is helpful to be able to translate IP addresses generated by normal routing
18402 mechanisms into other IP addresses, thus performing a kind of manual IP
18403 routing. This should be done only if the normal IP routing of the TCP/IP stack
18404 is inadequate or broken. Because this is an extremely uncommon requirement, the
18405 code to support this option is not included in the Exim binary unless
18406 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18408 .vindex "&$host_address$&"
18409 The &%translate_ip_address%& string is expanded for every IP address generated
18410 by the router, with the generated address set in &$host_address$&. If the
18411 expansion is forced to fail, no action is taken.
18412 For any other expansion error, delivery of the message is deferred.
18413 If the result of the expansion is an IP address, that replaces the original
18414 address; otherwise the result is assumed to be a host name &-- this is looked
18415 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18416 produce one or more replacement IP addresses. For example, to subvert all IP
18417 addresses in some specific networks, this could be added to a router:
18419 translate_ip_address = \
18420 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18423 The file would contain lines like
18425 10.2.3.128/26 some.host
18426 10.8.4.34/26 10.44.8.15
18428 You should not make use of this facility unless you really understand what you
18433 .option transport routers string&!! unset
18434 This option specifies the transport to be used when a router accepts an address
18435 and sets it up for delivery. A transport is never needed if a router is used
18436 only for verification. The value of the option is expanded at routing time,
18437 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18438 and result must be the name of one of the configured transports. If it is not,
18439 delivery is deferred.
18441 The &%transport%& option is not used by the &(redirect)& router, but it does
18442 have some private options that set up transports for pipe and file deliveries
18443 (see chapter &<<CHAPredirect>>&).
18447 .option transport_current_directory routers string&!! unset
18448 .cindex "current directory for local transport"
18449 This option associates a current directory with any address that is routed
18450 to a local transport. This can happen either because a transport is
18451 explicitly configured for the router, or because it generates a delivery to a
18452 file or a pipe. During the delivery process (that is, at transport time), this
18453 option string is expanded and is set as the current directory, unless
18454 overridden by a setting on the transport.
18455 If the expansion fails for any reason, including forced failure, an error is
18456 logged, and delivery is deferred.
18457 See chapter &<<CHAPenvironment>>& for details of the local delivery
18463 .option transport_home_directory routers string&!! "see below"
18464 .cindex "home directory" "for local transport"
18465 This option associates a home directory with any address that is routed to a
18466 local transport. This can happen either because a transport is explicitly
18467 configured for the router, or because it generates a delivery to a file or a
18468 pipe. During the delivery process (that is, at transport time), the option
18469 string is expanded and is set as the home directory, unless overridden by a
18470 setting of &%home_directory%& on the transport.
18471 If the expansion fails for any reason, including forced failure, an error is
18472 logged, and delivery is deferred.
18474 If the transport does not specify a home directory, and
18475 &%transport_home_directory%& is not set for the router, the home directory for
18476 the transport is taken from the password data if &%check_local_user%& is set for
18477 the router. Otherwise it is taken from &%router_home_directory%& if that option
18478 is set; if not, no home directory is set for the transport.
18480 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18486 .option unseen routers boolean&!! false
18487 .cindex "router" "carrying on after success"
18488 The result of string expansion for this option must be a valid boolean value,
18489 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18490 result causes an error, and delivery is deferred. If the expansion is forced to
18491 fail, the default value for the option (false) is used. Other failures cause
18492 delivery to be deferred.
18494 When this option is set true, routing does not cease if the router accepts the
18495 address. Instead, a copy of the incoming address is passed to the next router,
18496 overriding a false setting of &%more%&. There is little point in setting
18497 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18498 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18499 sometimes true and sometimes false).
18501 .cindex "copy of message (&%unseen%& option)"
18502 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18503 qualifier in filter files. It can be used to cause copies of messages to be
18504 delivered to some other destination, while also carrying out a normal delivery.
18505 In effect, the current address is made into a &"parent"& that has two children
18506 &-- one that is delivered as specified by this router, and a clone that goes on
18507 to be routed further. For this reason, &%unseen%& may not be combined with the
18508 &%one_time%& option in a &(redirect)& router.
18510 &*Warning*&: Header lines added to the address (or specified for removal) by
18511 this router or by previous routers affect the &"unseen"& copy of the message
18512 only. The clone that continues to be processed by further routers starts with
18513 no added headers and none specified for removal. For a &%redirect%& router, if
18514 a generated address is the same as the incoming address, this can lead to
18515 duplicate addresses with different header modifications. Exim does not do
18516 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18517 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18518 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18519 &%redirect%& router may be of help.
18521 Unlike the handling of header modifications, any data that was set by the
18522 &%address_data%& option in the current or previous routers &'is'& passed on to
18523 subsequent routers.
18526 .option user routers string&!! "see below"
18527 .cindex "uid (user id)" "local delivery"
18528 .cindex "local transports" "uid and gid"
18529 .cindex "transport" "local"
18530 .cindex "router" "user for filter processing"
18531 .cindex "filter" "user for processing"
18532 When a router queues an address for a transport, and the transport does not
18533 specify a user, the user given here is used when running the delivery process.
18534 The user may be specified numerically or by name. If expansion fails, the
18535 error is logged and delivery is deferred.
18536 This user is also used by the &(redirect)& router when running a filter file.
18537 The default is unset, except when &%check_local_user%& is set. In this case,
18538 the default is taken from the password information. If the user is specified as
18539 a name, and &%group%& is not set, the group associated with the user is used.
18540 See also &%initgroups%& and &%group%& and the discussion in chapter
18541 &<<CHAPenvironment>>&.
18545 .option verify routers&!? boolean true
18546 Setting this option has the effect of setting &%verify_sender%& and
18547 &%verify_recipient%& to the same value.
18550 .option verify_only routers&!? boolean false
18551 .cindex "EXPN" "with &%verify_only%&"
18553 .cindex "router" "used only when verifying"
18554 If this option is set, the router is used only when verifying an address,
18555 delivering in cutthrough mode or
18556 testing with the &%-bv%& option, not when actually doing a delivery, testing
18557 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18558 restricted to verifying only senders or recipients by means of
18559 &%verify_sender%& and &%verify_recipient%&.
18561 &*Warning*&: When the router is being run to verify addresses for an incoming
18562 SMTP message, Exim is not running as root, but under its own uid. If the router
18563 accesses any files, you need to make sure that they are accessible to the Exim
18567 .option verify_recipient routers&!? boolean true
18568 If this option is false, the router is skipped when verifying recipient
18570 delivering in cutthrough mode
18571 or testing recipient verification using &%-bv%&.
18572 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18574 See also the &$verify_mode$& variable.
18577 .option verify_sender routers&!? boolean true
18578 If this option is false, the router is skipped when verifying sender addresses
18579 or testing sender verification using &%-bvs%&.
18580 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18582 See also the &$verify_mode$& variable.
18583 .ecindex IIDgenoprou1
18584 .ecindex IIDgenoprou2
18591 . ////////////////////////////////////////////////////////////////////////////
18592 . ////////////////////////////////////////////////////////////////////////////
18594 .chapter "The accept router" "CHID4"
18595 .cindex "&(accept)& router"
18596 .cindex "routers" "&(accept)&"
18597 The &(accept)& router has no private options of its own. Unless it is being
18598 used purely for verification (see &%verify_only%&) a transport is required to
18599 be defined by the generic &%transport%& option. If the preconditions that are
18600 specified by generic options are met, the router accepts the address and queues
18601 it for the given transport. The most common use of this router is for setting
18602 up deliveries to local mailboxes. For example:
18606 domains = mydomain.example
18608 transport = local_delivery
18610 The &%domains%& condition in this example checks the domain of the address, and
18611 &%check_local_user%& checks that the local part is the login of a local user.
18612 When both preconditions are met, the &(accept)& router runs, and queues the
18613 address for the &(local_delivery)& transport.
18620 . ////////////////////////////////////////////////////////////////////////////
18621 . ////////////////////////////////////////////////////////////////////////////
18623 .chapter "The dnslookup router" "CHAPdnslookup"
18624 .scindex IIDdnsrou1 "&(dnslookup)& router"
18625 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18626 The &(dnslookup)& router looks up the hosts that handle mail for the
18627 recipient's domain in the DNS. A transport must always be set for this router,
18628 unless &%verify_only%& is set.
18630 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18631 SRV records. If none are found, or if SRV support is not configured,
18632 MX records are looked up. If no MX records exist, address records are sought.
18633 However, &%mx_domains%& can be set to disable the direct use of address
18636 MX records of equal priority are sorted by Exim into a random order. Exim then
18637 looks for address records for the host names obtained from MX or SRV records.
18638 When a host has more than one IP address, they are sorted into a random order,
18639 except that IPv6 addresses are always sorted before IPv4 addresses. If all the
18640 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18641 generic option, the router declines.
18643 Unless they have the highest priority (lowest MX value), MX records that point
18644 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18645 are discarded, together with any other MX records of equal or lower priority.
18647 .cindex "MX record" "pointing to local host"
18648 .cindex "local host" "MX pointing to"
18649 .oindex "&%self%&" "in &(dnslookup)& router"
18650 If the host pointed to by the highest priority MX record, or looked up as an
18651 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18652 happens is controlled by the generic &%self%& option.
18655 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18656 There have been problems with DNS servers when SRV records are looked up.
18657 Some misbehaving servers return a DNS error or timeout when a non-existent
18658 SRV record is sought. Similar problems have in the past been reported for
18659 MX records. The global &%dns_again_means_nonexist%& option can help with this
18660 problem, but it is heavy-handed because it is a global option.
18662 For this reason, there are two options, &%srv_fail_domains%& and
18663 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18664 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18665 an attempt to look up an SRV or MX record causes one of these results, and the
18666 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18667 such record"&. In the case of an SRV lookup, this means that the router
18668 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18669 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18670 case routing fails.
18673 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18674 .cindex "&(dnslookup)& router" "declines"
18675 There are a few cases where a &(dnslookup)& router will decline to accept
18676 an address; if such a router is expected to handle "all remaining non-local
18677 domains", then it is important to set &%no_more%&.
18679 The router will defer rather than decline if the domain
18680 is found in the &%fail_defer_domains%& router option.
18682 Reasons for a &(dnslookup)& router to decline currently include:
18684 The domain does not exist in DNS
18686 The domain exists but the MX record's host part is just "."; this is a common
18687 convention (borrowed from SRV) used to indicate that there is no such service
18688 for this domain and to not fall back to trying A/AAAA records.
18690 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18692 MX record points to a non-existent host.
18694 MX record points to an IP address and the main section option
18695 &%allow_mx_to_ip%& is not set.
18697 MX records exist and point to valid hosts, but all hosts resolve only to
18698 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18700 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18701 &%dns_check_names_pattern%& for handling one variant of this)
18703 &%check_secondary_mx%& is set on this router but the local host can
18704 not be found in the MX records (see below)
18710 .section "Private options for dnslookup" "SECID118"
18711 .cindex "options" "&(dnslookup)& router"
18712 The private options for the &(dnslookup)& router are as follows:
18714 .option check_secondary_mx dnslookup boolean false
18715 .cindex "MX record" "checking for secondary"
18716 If this option is set, the router declines unless the local host is found in
18717 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18718 process domains for which the local host is a secondary mail exchanger
18719 differently to other domains. The way in which Exim decides whether a host is
18720 the local host is described in section &<<SECTreclocipadd>>&.
18723 .option check_srv dnslookup string&!! unset
18724 .cindex "SRV record" "enabling use of"
18725 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18726 addition to MX and address records. The support is disabled by default. To
18727 enable SRV support, set the &%check_srv%& option to the name of the service
18728 required. For example,
18732 looks for SRV records that refer to the normal smtp service. The option is
18733 expanded, so the service name can vary from message to message or address
18734 to address. This might be helpful if SRV records are being used for a
18735 submission service. If the expansion is forced to fail, the &%check_srv%&
18736 option is ignored, and the router proceeds to look for MX records in the
18739 When the expansion succeeds, the router searches first for SRV records for
18740 the given service (it assumes TCP protocol). A single SRV record with a
18741 host name that consists of just a single dot indicates &"no such service for
18742 this domain"&; if this is encountered, the router declines. If other kinds of
18743 SRV record are found, they are used to construct a host list for delivery
18744 according to the rules of RFC 2782. MX records are not sought in this case.
18746 When no SRV records are found, MX records (and address records) are sought in
18747 the traditional way. In other words, SRV records take precedence over MX
18748 records, just as MX records take precedence over address records. Note that
18749 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18750 defined it. It is apparently believed that MX records are sufficient for email
18751 and that SRV records should not be used for this purpose. However, SRV records
18752 have an additional &"weight"& feature which some people might find useful when
18753 trying to split an SMTP load between hosts of different power.
18755 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18756 when there is a DNS lookup error.
18761 .option fail_defer_domains dnslookup "domain list&!!" unset
18762 .cindex "MX record" "not found"
18763 DNS lookups for domains matching &%fail_defer_domains%&
18764 which find no matching record will cause the router to defer
18765 rather than the default behaviour of decline.
18766 This maybe be useful for queueing messages for a newly created
18767 domain while the DNS configuration is not ready.
18768 However, it will result in any message with mistyped domains
18772 .option mx_domains dnslookup "domain list&!!" unset
18773 .cindex "MX record" "required to exist"
18774 .cindex "SRV record" "required to exist"
18775 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
18776 record in order to be recognized. (The name of this option could be improved.)
18777 For example, if all the mail hosts in &'fict.example'& are known to have MX
18778 records, except for those in &'discworld.fict.example'&, you could use this
18781 mx_domains = ! *.discworld.fict.example : *.fict.example
18783 This specifies that messages addressed to a domain that matches the list but
18784 has no MX record should be bounced immediately instead of being routed using
18785 the address record.
18788 .option mx_fail_domains dnslookup "domain list&!!" unset
18789 If the DNS lookup for MX records for one of the domains in this list causes a
18790 DNS lookup error, Exim behaves as if no MX records were found. See section
18791 &<<SECTprowitdnsloo>>& for more discussion.
18796 .option qualify_single dnslookup boolean true
18797 .cindex "DNS" "resolver options"
18798 .cindex "DNS" "qualifying single-component names"
18799 When this option is true, the resolver option RES_DEFNAMES is set for DNS
18800 lookups. Typically, but not standardly, this causes the resolver to qualify
18801 single-component names with the default domain. For example, on a machine
18802 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
18803 &'thesaurus.ref.example'& inside the resolver. For details of what your
18804 resolver actually does, consult your man pages for &'resolver'& and
18809 .option rewrite_headers dnslookup boolean true
18810 .cindex "rewriting" "header lines"
18811 .cindex "header lines" "rewriting"
18812 If the domain name in the address that is being processed is not fully
18813 qualified, it may be expanded to its full form by a DNS lookup. For example, if
18814 an address is specified as &'dormouse@teaparty'&, the domain might be
18815 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
18816 occur as a result of setting the &%widen_domains%& option. If
18817 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
18818 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
18819 header lines of the message are rewritten with the full domain name.
18821 This option should be turned off only when it is known that no message is
18822 ever going to be sent outside an environment where the abbreviation makes
18825 When an MX record is looked up in the DNS and matches a wildcard record, name
18826 servers normally return a record containing the name that has been looked up,
18827 making it impossible to detect whether a wildcard was present or not. However,
18828 some name servers have recently been seen to return the wildcard entry. If the
18829 name returned by a DNS lookup begins with an asterisk, it is not used for
18833 .option same_domain_copy_routing dnslookup boolean false
18834 .cindex "address" "copying routing"
18835 Addresses with the same domain are normally routed by the &(dnslookup)& router
18836 to the same list of hosts. However, this cannot be presumed, because the router
18837 options and preconditions may refer to the local part of the address. By
18838 default, therefore, Exim routes each address in a message independently. DNS
18839 servers run caches, so repeated DNS lookups are not normally expensive, and in
18840 any case, personal messages rarely have more than a few recipients.
18842 If you are running mailing lists with large numbers of subscribers at the same
18843 domain, and you are using a &(dnslookup)& router which is independent of the
18844 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
18845 lookups for identical domains in one message. In this case, when &(dnslookup)&
18846 routes an address to a remote transport, any other unrouted addresses in the
18847 message that have the same domain are automatically given the same routing
18848 without processing them independently,
18849 provided the following conditions are met:
18852 No router that processed the address specified &%headers_add%& or
18853 &%headers_remove%&.
18855 The router did not change the address in any way, for example, by &"widening"&
18862 .option search_parents dnslookup boolean false
18863 .cindex "DNS" "resolver options"
18864 When this option is true, the resolver option RES_DNSRCH is set for DNS
18865 lookups. This is different from the &%qualify_single%& option in that it
18866 applies to domains containing dots. Typically, but not standardly, it causes
18867 the resolver to search for the name in the current domain and in parent
18868 domains. For example, on a machine in the &'fict.example'& domain, if looking
18869 up &'teaparty.wonderland'& failed, the resolver would try
18870 &'teaparty.wonderland.fict.example'&. For details of what your resolver
18871 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
18873 Setting this option true can cause problems in domains that have a wildcard MX
18874 record, because any domain that does not have its own MX record matches the
18879 .option srv_fail_domains dnslookup "domain list&!!" unset
18880 If the DNS lookup for SRV records for one of the domains in this list causes a
18881 DNS lookup error, Exim behaves as if no SRV records were found. See section
18882 &<<SECTprowitdnsloo>>& for more discussion.
18887 .option widen_domains dnslookup "string list" unset
18888 .cindex "domain" "partial; widening"
18889 If a DNS lookup fails and this option is set, each of its strings in turn is
18890 added onto the end of the domain, and the lookup is tried again. For example,
18893 widen_domains = fict.example:ref.example
18895 is set and a lookup of &'klingon.dictionary'& fails,
18896 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
18897 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
18898 and &%search_parents%& options can cause some widening to be undertaken inside
18899 the DNS resolver. &%widen_domains%& is not applied to sender addresses
18900 when verifying, unless &%rewrite_headers%& is false (not the default).
18903 .section "Effect of qualify_single and search_parents" "SECID119"
18904 When a domain from an envelope recipient is changed by the resolver as a result
18905 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
18906 corresponding address in the message's header lines unless &%rewrite_headers%&
18907 is set false. Exim then re-routes the address, using the full domain.
18909 These two options affect only the DNS lookup that takes place inside the router
18910 for the domain of the address that is being routed. They do not affect lookups
18911 such as that implied by
18915 that may happen while processing a router precondition before the router is
18916 entered. No widening ever takes place for these lookups.
18917 .ecindex IIDdnsrou1
18918 .ecindex IIDdnsrou2
18928 . ////////////////////////////////////////////////////////////////////////////
18929 . ////////////////////////////////////////////////////////////////////////////
18931 .chapter "The ipliteral router" "CHID5"
18932 .cindex "&(ipliteral)& router"
18933 .cindex "domain literal" "routing"
18934 .cindex "routers" "&(ipliteral)&"
18935 This router has no private options. Unless it is being used purely for
18936 verification (see &%verify_only%&) a transport is required to be defined by the
18937 generic &%transport%& option. The router accepts the address if its domain part
18938 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
18939 router handles the address
18943 by setting up delivery to the host with that IP address. IPv4 domain literals
18944 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
18945 are similar, but the address is preceded by &`ipv6:`&. For example:
18947 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
18949 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
18950 grounds that sooner or later somebody will try it.
18952 .oindex "&%self%&" "in &(ipliteral)& router"
18953 If the IP address matches something in &%ignore_target_hosts%&, the router
18954 declines. If an IP literal turns out to refer to the local host, the generic
18955 &%self%& option determines what happens.
18957 The RFCs require support for domain literals; however, their use is
18958 controversial in today's Internet. If you want to use this router, you must
18959 also set the main configuration option &%allow_domain_literals%&. Otherwise,
18960 Exim will not recognize the domain literal syntax in addresses.
18964 . ////////////////////////////////////////////////////////////////////////////
18965 . ////////////////////////////////////////////////////////////////////////////
18967 .chapter "The iplookup router" "CHID6"
18968 .cindex "&(iplookup)& router"
18969 .cindex "routers" "&(iplookup)&"
18970 The &(iplookup)& router was written to fulfil a specific requirement in
18971 Cambridge University (which in fact no longer exists). For this reason, it is
18972 not included in the binary of Exim by default. If you want to include it, you
18975 ROUTER_IPLOOKUP=yes
18977 in your &_Local/Makefile_& configuration file.
18979 The &(iplookup)& router routes an address by sending it over a TCP or UDP
18980 connection to one or more specific hosts. The host can then return the same or
18981 a different address &-- in effect rewriting the recipient address in the
18982 message's envelope. The new address is then passed on to subsequent routers. If
18983 this process fails, the address can be passed on to other routers, or delivery
18984 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
18985 must not be specified for it.
18987 .cindex "options" "&(iplookup)& router"
18988 .option hosts iplookup string unset
18989 This option must be supplied. Its value is a colon-separated list of host
18990 names. The hosts are looked up using &[gethostbyname()]&
18991 (or &[getipnodebyname()]& when available)
18992 and are tried in order until one responds to the query. If none respond, what
18993 happens is controlled by &%optional%&.
18996 .option optional iplookup boolean false
18997 If &%optional%& is true, if no response is obtained from any host, the address
18998 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
18999 delivery to the address is deferred.
19002 .option port iplookup integer 0
19003 .cindex "port" "&(iplookup)& router"
19004 This option must be supplied. It specifies the port number for the TCP or UDP
19008 .option protocol iplookup string udp
19009 This option can be set to &"udp"& or &"tcp"& to specify which of the two
19010 protocols is to be used.
19013 .option query iplookup string&!! "see below"
19014 This defines the content of the query that is sent to the remote hosts. The
19017 $local_part@$domain $local_part@$domain
19019 The repetition serves as a way of checking that a response is to the correct
19020 query in the default case (see &%response_pattern%& below).
19023 .option reroute iplookup string&!! unset
19024 If this option is not set, the rerouted address is precisely the byte string
19025 returned by the remote host, up to the first white space, if any. If set, the
19026 string is expanded to form the rerouted address. It can include parts matched
19027 in the response by &%response_pattern%& by means of numeric variables such as
19028 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
19029 whether or not a pattern is in use. In all cases, the rerouted address must end
19030 up in the form &'local_part@domain'&.
19033 .option response_pattern iplookup string unset
19034 This option can be set to a regular expression that is applied to the string
19035 returned from the remote host. If the pattern does not match the response, the
19036 router declines. If &%response_pattern%& is not set, no checking of the
19037 response is done, unless the query was defaulted, in which case there is a
19038 check that the text returned after the first white space is the original
19039 address. This checks that the answer that has been received is in response to
19040 the correct question. For example, if the response is just a new domain, the
19041 following could be used:
19043 response_pattern = ^([^@]+)$
19044 reroute = $local_part@$1
19047 .option timeout iplookup time 5s
19048 This specifies the amount of time to wait for a response from the remote
19049 machine. The same timeout is used for the &[connect()]& function for a TCP
19050 call. It does not apply to UDP.
19055 . ////////////////////////////////////////////////////////////////////////////
19056 . ////////////////////////////////////////////////////////////////////////////
19058 .chapter "The manualroute router" "CHID7"
19059 .scindex IIDmanrou1 "&(manualroute)& router"
19060 .scindex IIDmanrou2 "routers" "&(manualroute)&"
19061 .cindex "domain" "manually routing"
19062 The &(manualroute)& router is so-called because it provides a way of manually
19063 routing an address according to its domain. It is mainly used when you want to
19064 route addresses to remote hosts according to your own rules, bypassing the
19065 normal DNS routing that looks up MX records. However, &(manualroute)& can also
19066 route to local transports, a facility that may be useful if you want to save
19067 messages for dial-in hosts in local files.
19069 The &(manualroute)& router compares a list of domain patterns with the domain
19070 it is trying to route. If there is no match, the router declines. Each pattern
19071 has associated with it a list of hosts and some other optional data, which may
19072 include a transport. The combination of a pattern and its data is called a
19073 &"routing rule"&. For patterns that do not have an associated transport, the
19074 generic &%transport%& option must specify a transport, unless the router is
19075 being used purely for verification (see &%verify_only%&).
19078 In the case of verification, matching the domain pattern is sufficient for the
19079 router to accept the address. When actually routing an address for delivery,
19080 an address that matches a domain pattern is queued for the associated
19081 transport. If the transport is not a local one, a host list must be associated
19082 with the pattern; IP addresses are looked up for the hosts, and these are
19083 passed to the transport along with the mail address. For local transports, a
19084 host list is optional. If it is present, it is passed in &$host$& as a single
19087 The list of routing rules can be provided as an inline string in
19088 &%route_list%&, or the data can be obtained by looking up the domain in a file
19089 or database by setting &%route_data%&. Only one of these settings may appear in
19090 any one instance of &(manualroute)&. The format of routing rules is described
19091 below, following the list of private options.
19094 .section "Private options for manualroute" "SECTprioptman"
19096 .cindex "options" "&(manualroute)& router"
19097 The private options for the &(manualroute)& router are as follows:
19099 .option host_all_ignored manualroute string defer
19100 See &%host_find_failed%&.
19102 .option host_find_failed manualroute string freeze
19103 This option controls what happens when &(manualroute)& tries to find an IP
19104 address for a host, and the host does not exist. The option can be set to one
19105 of the following values:
19114 The default (&"freeze"&) assumes that this state is a serious configuration
19115 error. The difference between &"pass"& and &"decline"& is that the former
19116 forces the address to be passed to the next router (or the router defined by
19119 overriding &%no_more%&, whereas the latter passes the address to the next
19120 router only if &%more%& is true.
19122 The value &"ignore"& causes Exim to completely ignore a host whose IP address
19123 cannot be found. If all the hosts in the list are ignored, the behaviour is
19124 controlled by the &%host_all_ignored%& option. This takes the same values
19125 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
19127 The &%host_find_failed%& option applies only to a definite &"does not exist"&
19128 state; if a host lookup gets a temporary error, delivery is deferred unless the
19129 generic &%pass_on_timeout%& option is set.
19132 .option hosts_randomize manualroute boolean false
19133 .cindex "randomized host list"
19134 .cindex "host" "list of; randomized"
19135 If this option is set, the order of the items in a host list in a routing rule
19136 is randomized each time the list is used, unless an option in the routing rule
19137 overrides (see below). Randomizing the order of a host list can be used to do
19138 crude load sharing. However, if more than one mail address is routed by the
19139 same router to the same host list, the host lists are considered to be the same
19140 (even though they may be randomized into different orders) for the purpose of
19141 deciding whether to batch the deliveries into a single SMTP transaction.
19143 When &%hosts_randomize%& is true, a host list may be split
19144 into groups whose order is separately randomized. This makes it possible to
19145 set up MX-like behaviour. The boundaries between groups are indicated by an
19146 item that is just &`+`& in the host list. For example:
19148 route_list = * host1:host2:host3:+:host4:host5
19150 The order of the first three hosts and the order of the last two hosts is
19151 randomized for each use, but the first three always end up before the last two.
19152 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
19153 randomized host list is passed to an &(smtp)& transport that also has
19154 &%hosts_randomize set%&, the list is not re-randomized.
19157 .option route_data manualroute string&!! unset
19158 If this option is set, it must expand to yield the data part of a routing rule.
19159 Typically, the expansion string includes a lookup based on the domain. For
19162 route_data = ${lookup{$domain}dbm{/etc/routes}}
19164 If the expansion is forced to fail, or the result is an empty string, the
19165 router declines. Other kinds of expansion failure cause delivery to be
19169 .option route_list manualroute "string list" unset
19170 This string is a list of routing rules, in the form defined below. Note that,
19171 unlike most string lists, the items are separated by semicolons. This is so
19172 that they may contain colon-separated host lists.
19175 .option same_domain_copy_routing manualroute boolean false
19176 .cindex "address" "copying routing"
19177 Addresses with the same domain are normally routed by the &(manualroute)&
19178 router to the same list of hosts. However, this cannot be presumed, because the
19179 router options and preconditions may refer to the local part of the address. By
19180 default, therefore, Exim routes each address in a message independently. DNS
19181 servers run caches, so repeated DNS lookups are not normally expensive, and in
19182 any case, personal messages rarely have more than a few recipients.
19184 If you are running mailing lists with large numbers of subscribers at the same
19185 domain, and you are using a &(manualroute)& router which is independent of the
19186 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19187 lookups for identical domains in one message. In this case, when
19188 &(manualroute)& routes an address to a remote transport, any other unrouted
19189 addresses in the message that have the same domain are automatically given the
19190 same routing without processing them independently. However, this is only done
19191 if &%headers_add%& and &%headers_remove%& are unset.
19196 .section "Routing rules in route_list" "SECID120"
19197 The value of &%route_list%& is a string consisting of a sequence of routing
19198 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
19199 entered as two semicolons. Alternatively, the list separator can be changed as
19200 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
19201 Empty rules are ignored. The format of each rule is
19203 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
19205 The following example contains two rules, each with a simple domain pattern and
19209 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
19210 thes.ref.example mail-3.ref.example:mail-4.ref.example
19212 The three parts of a rule are separated by white space. The pattern and the
19213 list of hosts can be enclosed in quotes if necessary, and if they are, the
19214 usual quoting rules apply. Each rule in a &%route_list%& must start with a
19215 single domain pattern, which is the only mandatory item in the rule. The
19216 pattern is in the same format as one item in a domain list (see section
19217 &<<SECTdomainlist>>&),
19218 except that it may not be the name of an interpolated file.
19219 That is, it may be wildcarded, or a regular expression, or a file or database
19220 lookup (with semicolons doubled, because of the use of semicolon as a separator
19221 in a &%route_list%&).
19223 The rules in &%route_list%& are searched in order until one of the patterns
19224 matches the domain that is being routed. The list of hosts and then options are
19225 then used as described below. If there is no match, the router declines. When
19226 &%route_list%& is set, &%route_data%& must not be set.
19230 .section "Routing rules in route_data" "SECID121"
19231 The use of &%route_list%& is convenient when there are only a small number of
19232 routing rules. For larger numbers, it is easier to use a file or database to
19233 hold the routing information, and use the &%route_data%& option instead.
19234 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19235 Most commonly, &%route_data%& is set as a string that contains an
19236 expansion lookup. For example, suppose we place two routing rules in a file
19239 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19240 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19242 This data can be accessed by setting
19244 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19246 Failure of the lookup results in an empty string, causing the router to
19247 decline. However, you do not have to use a lookup in &%route_data%&. The only
19248 requirement is that the result of expanding the string is a list of hosts,
19249 possibly followed by options, separated by white space. The list of hosts must
19250 be enclosed in quotes if it contains white space.
19255 .section "Format of the list of hosts" "SECID122"
19256 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19257 always separately expanded before use. If the expansion fails, the router
19258 declines. The result of the expansion must be a colon-separated list of names
19259 and/or IP addresses, optionally also including ports. The format of each item
19260 in the list is described in the next section. The list separator can be changed
19261 as described in section &<<SECTlistconstruct>>&.
19263 If the list of hosts was obtained from a &%route_list%& item, the following
19264 variables are set during its expansion:
19267 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19268 If the domain was matched against a regular expression, the numeric variables
19269 &$1$&, &$2$&, etc. may be set. For example:
19271 route_list = ^domain(\d+) host-$1.text.example
19274 &$0$& is always set to the entire domain.
19276 &$1$& is also set when partial matching is done in a file lookup.
19279 .vindex "&$value$&"
19280 If the pattern that matched the domain was a lookup item, the data that was
19281 looked up is available in the expansion variable &$value$&. For example:
19283 route_list = lsearch;;/some/file.routes $value
19287 Note the doubling of the semicolon in the pattern that is necessary because
19288 semicolon is the default route list separator.
19292 .section "Format of one host item" "SECTformatonehostitem"
19293 Each item in the list of hosts is either a host name or an IP address,
19294 optionally with an attached port number. When no port is given, an IP address
19295 is not enclosed in brackets. When a port is specified, it overrides the port
19296 specification on the transport. The port is separated from the name or address
19297 by a colon. This leads to some complications:
19300 Because colon is the default separator for the list of hosts, either
19301 the colon that specifies a port must be doubled, or the list separator must
19302 be changed. The following two examples have the same effect:
19304 route_list = * "host1.tld::1225 : host2.tld::1226"
19305 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19308 When IPv6 addresses are involved, it gets worse, because they contain
19309 colons of their own. To make this case easier, it is permitted to
19310 enclose an IP address (either v4 or v6) in square brackets if a port
19311 number follows. For example:
19313 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19317 .section "How the list of hosts is used" "SECThostshowused"
19318 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19319 the hosts is tried, in the order specified, when carrying out the SMTP
19320 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19321 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19324 Hosts may be listed by name or by IP address. An unadorned name in the list of
19325 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19326 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19327 records in the DNS. For example:
19329 route_list = * x.y.z:p.q.r/MX:e.f.g
19331 If this feature is used with a port specifier, the port must come last. For
19334 route_list = * dom1.tld/mx::1225
19336 If the &%hosts_randomize%& option is set, the order of the items in the list is
19337 randomized before any lookups are done. Exim then scans the list; for any name
19338 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19339 be an interface on the local host and the item is not the first in the list,
19340 Exim discards it and any subsequent items. If it is the first item, what
19341 happens is controlled by the
19342 .oindex "&%self%&" "in &(manualroute)& router"
19343 &%self%& option of the router.
19345 A name on the list that is followed by &`/MX`& is replaced with the list of
19346 hosts obtained by looking up MX records for the name. This is always a DNS
19347 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19348 below) are not relevant here. The order of these hosts is determined by the
19349 preference values in the MX records, according to the usual rules. Because
19350 randomizing happens before the MX lookup, it does not affect the order that is
19351 defined by MX preferences.
19353 If the local host is present in the sublist obtained from MX records, but is
19354 not the most preferred host in that list, it and any equally or less
19355 preferred hosts are removed before the sublist is inserted into the main list.
19357 If the local host is the most preferred host in the MX list, what happens
19358 depends on where in the original list of hosts the &`/MX`& item appears. If it
19359 is not the first item (that is, there are previous hosts in the main list),
19360 Exim discards this name and any subsequent items in the main list.
19362 If the MX item is first in the list of hosts, and the local host is the
19363 most preferred host, what happens is controlled by the &%self%& option of the
19366 DNS failures when lookup up the MX records are treated in the same way as DNS
19367 failures when looking up IP addresses: &%pass_on_timeout%& and
19368 &%host_find_failed%& are used when relevant.
19370 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19371 whether obtained from an MX lookup or not.
19375 .section "How the options are used" "SECThowoptused"
19376 The options are a sequence of words; in practice no more than three are ever
19377 present. One of the words can be the name of a transport; this overrides the
19378 &%transport%& option on the router for this particular routing rule only. The
19379 other words (if present) control randomization of the list of hosts on a
19380 per-rule basis, and how the IP addresses of the hosts are to be found when
19381 routing to a remote transport. These options are as follows:
19384 &%randomize%&: randomize the order of the hosts in this list, overriding the
19385 setting of &%hosts_randomize%& for this routing rule only.
19387 &%no_randomize%&: do not randomize the order of the hosts in this list,
19388 overriding the setting of &%hosts_randomize%& for this routing rule only.
19390 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19391 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19392 also look in &_/etc/hosts_& or other sources of information.
19394 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19395 no address records are found. If there is a temporary DNS error (such as a
19396 timeout), delivery is deferred.
19401 route_list = domain1 host1:host2:host3 randomize bydns;\
19402 domain2 host4:host5
19404 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19405 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19406 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19407 or &[gethostbyname()]&, and the result of the lookup is the result of that
19410 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19411 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19412 instead of TRY_AGAIN. That is why the default action is to try a DNS
19413 lookup first. Only if that gives a definite &"no such host"& is the local
19418 If no IP address for a host can be found, what happens is controlled by the
19419 &%host_find_failed%& option.
19422 When an address is routed to a local transport, IP addresses are not looked up.
19423 The host list is passed to the transport in the &$host$& variable.
19427 .section "Manualroute examples" "SECID123"
19428 In some of the examples that follow, the presence of the &%remote_smtp%&
19429 transport, as defined in the default configuration file, is assumed:
19432 .cindex "smart host" "example router"
19433 The &(manualroute)& router can be used to forward all external mail to a
19434 &'smart host'&. If you have set up, in the main part of the configuration, a
19435 named domain list that contains your local domains, for example:
19437 domainlist local_domains = my.domain.example
19439 You can arrange for all other domains to be routed to a smart host by making
19440 your first router something like this:
19443 driver = manualroute
19444 domains = !+local_domains
19445 transport = remote_smtp
19446 route_list = * smarthost.ref.example
19448 This causes all non-local addresses to be sent to the single host
19449 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19450 they are tried in order
19451 (but you can use &%hosts_randomize%& to vary the order each time).
19452 Another way of configuring the same thing is this:
19455 driver = manualroute
19456 transport = remote_smtp
19457 route_list = !+local_domains smarthost.ref.example
19459 There is no difference in behaviour between these two routers as they stand.
19460 However, they behave differently if &%no_more%& is added to them. In the first
19461 example, the router is skipped if the domain does not match the &%domains%&
19462 precondition; the following router is always tried. If the router runs, it
19463 always matches the domain and so can never decline. Therefore, &%no_more%&
19464 would have no effect. In the second case, the router is never skipped; it
19465 always runs. However, if it doesn't match the domain, it declines. In this case
19466 &%no_more%& would prevent subsequent routers from running.
19469 .cindex "mail hub example"
19470 A &'mail hub'& is a host which receives mail for a number of domains via MX
19471 records in the DNS and delivers it via its own private routing mechanism. Often
19472 the final destinations are behind a firewall, with the mail hub being the one
19473 machine that can connect to machines both inside and outside the firewall. The
19474 &(manualroute)& router is usually used on a mail hub to route incoming messages
19475 to the correct hosts. For a small number of domains, the routing can be inline,
19476 using the &%route_list%& option, but for a larger number a file or database
19477 lookup is easier to manage.
19479 If the domain names are in fact the names of the machines to which the mail is
19480 to be sent by the mail hub, the configuration can be quite simple. For
19484 driver = manualroute
19485 transport = remote_smtp
19486 route_list = *.rhodes.tvs.example $domain
19488 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19489 whose names are the same as the mail domains. A similar approach can be taken
19490 if the host name can be obtained from the domain name by a string manipulation
19491 that the expansion facilities can handle. Otherwise, a lookup based on the
19492 domain can be used to find the host:
19495 driver = manualroute
19496 transport = remote_smtp
19497 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19499 The result of the lookup must be the name or IP address of the host (or
19500 hosts) to which the address is to be routed. If the lookup fails, the route
19501 data is empty, causing the router to decline. The address then passes to the
19505 .cindex "batched SMTP output example"
19506 .cindex "SMTP" "batched outgoing; example"
19507 You can use &(manualroute)& to deliver messages to pipes or files in batched
19508 SMTP format for onward transportation by some other means. This is one way of
19509 storing mail for a dial-up host when it is not connected. The route list entry
19510 can be as simple as a single domain name in a configuration like this:
19513 driver = manualroute
19514 transport = batchsmtp_appendfile
19515 route_list = saved.domain.example
19517 though often a pattern is used to pick up more than one domain. If there are
19518 several domains or groups of domains with different transport requirements,
19519 different transports can be listed in the routing information:
19522 driver = manualroute
19524 *.saved.domain1.example $domain batch_appendfile; \
19525 *.saved.domain2.example \
19526 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19529 .vindex "&$domain$&"
19531 The first of these just passes the domain in the &$host$& variable, which
19532 doesn't achieve much (since it is also in &$domain$&), but the second does a
19533 file lookup to find a value to pass, causing the router to decline to handle
19534 the address if the lookup fails.
19537 .cindex "UUCP" "example of router for"
19538 Routing mail directly to UUCP software is a specific case of the use of
19539 &(manualroute)& in a gateway to another mail environment. This is an example of
19540 one way it can be done:
19546 command = /usr/local/bin/uux -r - \
19547 ${substr_-5:$host}!rmail ${local_part}
19548 return_fail_output = true
19553 driver = manualroute
19555 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19557 The file &_/usr/local/exim/uucphosts_& contains entries like
19559 darksite.ethereal.example: darksite.UUCP
19561 It can be set up more simply without adding and removing &".UUCP"& but this way
19562 makes clear the distinction between the domain name
19563 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19565 .ecindex IIDmanrou1
19566 .ecindex IIDmanrou2
19575 . ////////////////////////////////////////////////////////////////////////////
19576 . ////////////////////////////////////////////////////////////////////////////
19578 .chapter "The queryprogram router" "CHAPdriverlast"
19579 .scindex IIDquerou1 "&(queryprogram)& router"
19580 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19581 .cindex "routing" "by external program"
19582 The &(queryprogram)& router routes an address by running an external command
19583 and acting on its output. This is an expensive way to route, and is intended
19584 mainly for use in lightly-loaded systems, or for performing experiments.
19585 However, if it is possible to use the precondition options (&%domains%&,
19586 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19587 be used in special cases, even on a busy host. There are the following private
19589 .cindex "options" "&(queryprogram)& router"
19591 .option command queryprogram string&!! unset
19592 This option must be set. It specifies the command that is to be run. The
19593 command is split up into a command name and arguments, and then each is
19594 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19595 &<<CHAPpipetransport>>&).
19598 .option command_group queryprogram string unset
19599 .cindex "gid (group id)" "in &(queryprogram)& router"
19600 This option specifies a gid to be set when running the command while routing an
19601 address for deliver. It must be set if &%command_user%& specifies a numerical
19602 uid. If it begins with a digit, it is interpreted as the numerical value of the
19603 gid. Otherwise it is looked up using &[getgrnam()]&.
19606 .option command_user queryprogram string unset
19607 .cindex "uid (user id)" "for &(queryprogram)&"
19608 This option must be set. It specifies the uid which is set when running the
19609 command while routing an address for delivery. If the value begins with a digit,
19610 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19611 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19612 not set, a value for the gid also.
19614 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19615 root, which it does during a normal delivery in a conventional configuration.
19616 However, when an address is being verified during message reception, Exim is
19617 usually running as the Exim user, not as root. If the &(queryprogram)& router
19618 is called from a non-root process, Exim cannot change uid or gid before running
19619 the command. In this circumstance the command runs under the current uid and
19623 .option current_directory queryprogram string /
19624 This option specifies an absolute path which is made the current directory
19625 before running the command.
19628 .option timeout queryprogram time 1h
19629 If the command does not complete within the timeout period, its process group
19630 is killed and the message is frozen. A value of zero time specifies no
19634 The standard output of the command is connected to a pipe, which is read when
19635 the command terminates. It should consist of a single line of output,
19636 containing up to five fields, separated by white space. The maximum length of
19637 the line is 1023 characters. Longer lines are silently truncated. The first
19638 field is one of the following words (case-insensitive):
19641 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19644 &'Decline'&: the router declines; pass the address to the next router, unless
19645 &%no_more%& is set.
19647 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19648 subsequent text on the line is an error message. If the router is run as part
19649 of address verification during an incoming SMTP message, the message is
19650 included in the SMTP response.
19652 &'Defer'&: routing could not be completed at this time; try again later. Any
19653 subsequent text on the line is an error message which is logged. It is not
19654 included in any SMTP response.
19656 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19658 &'Pass'&: pass the address to the next router (or the router specified by
19659 &%pass_router%&), overriding &%no_more%&.
19661 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19662 new addresses, which are routed independently, starting with the first router,
19663 or the router specified by &%redirect_router%&, if set.
19666 When the first word is &'accept'&, the remainder of the line consists of a
19667 number of keyed data values, as follows (split into two lines here, to fit on
19670 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19671 LOOKUP=byname|bydns DATA=<text>
19673 The data items can be given in any order, and all are optional. If no transport
19674 is included, the transport specified by the generic &%transport%& option is
19675 used. The list of hosts and the lookup type are needed only if the transport is
19676 an &(smtp)& transport that does not itself supply a list of hosts.
19678 The format of the list of hosts is the same as for the &(manualroute)& router.
19679 As well as host names and IP addresses with optional port numbers, as described
19680 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19681 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19682 (see section &<<SECThostshowused>>&).
19684 If the lookup type is not specified, Exim behaves as follows when trying to
19685 find an IP address for each host: First, a DNS lookup is done. If this yields
19686 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19687 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19688 result of the lookup is the result of that call.
19690 .vindex "&$address_data$&"
19691 If the DATA field is set, its value is placed in the &$address_data$&
19692 variable. For example, this return line
19694 accept hosts=x1.y.example:x2.y.example data="rule1"
19696 routes the address to the default transport, passing a list of two hosts. When
19697 the transport runs, the string &"rule1"& is in &$address_data$&.
19698 .ecindex IIDquerou1
19699 .ecindex IIDquerou2
19704 . ////////////////////////////////////////////////////////////////////////////
19705 . ////////////////////////////////////////////////////////////////////////////
19707 .chapter "The redirect router" "CHAPredirect"
19708 .scindex IIDredrou1 "&(redirect)& router"
19709 .scindex IIDredrou2 "routers" "&(redirect)&"
19710 .cindex "alias file" "in a &(redirect)& router"
19711 .cindex "address redirection" "&(redirect)& router"
19712 The &(redirect)& router handles several kinds of address redirection. Its most
19713 common uses are for resolving local part aliases from a central alias file
19714 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19715 files, but it has many other potential uses. The incoming address can be
19716 redirected in several different ways:
19719 It can be replaced by one or more new addresses which are themselves routed
19722 It can be routed to be delivered to a given file or directory.
19724 It can be routed to be delivered to a specified pipe command.
19726 It can cause an automatic reply to be generated.
19728 It can be forced to fail, optionally with a custom error message.
19730 It can be temporarily deferred, optionally with a custom message.
19732 It can be discarded.
19735 The generic &%transport%& option must not be set for &(redirect)& routers.
19736 However, there are some private options which define transports for delivery to
19737 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19738 &%pipe_transport%& and &%reply_transport%& descriptions below.
19740 If success DSNs have been requested
19741 .cindex "DSN" "success"
19742 .cindex "Delivery Status Notification" "success"
19743 redirection triggers one and the DSN options are not passed any further.
19747 .section "Redirection data" "SECID124"
19748 The router operates by interpreting a text string which it obtains either by
19749 expanding the contents of the &%data%& option, or by reading the entire
19750 contents of a file whose name is given in the &%file%& option. These two
19751 options are mutually exclusive. The first is commonly used for handling system
19752 aliases, in a configuration like this:
19756 data = ${lookup{$local_part}lsearch{/etc/aliases}}
19758 If the lookup fails, the expanded string in this example is empty. When the
19759 expansion of &%data%& results in an empty string, the router declines. A forced
19760 expansion failure also causes the router to decline; other expansion failures
19761 cause delivery to be deferred.
19763 A configuration using &%file%& is commonly used for handling users'
19764 &_.forward_& files, like this:
19769 file = $home/.forward
19772 If the file does not exist, or causes no action to be taken (for example, it is
19773 empty or consists only of comments), the router declines. &*Warning*&: This
19774 is not the case when the file contains syntactically valid items that happen to
19775 yield empty addresses, for example, items containing only RFC 2822 address
19780 .section "Forward files and address verification" "SECID125"
19781 .cindex "address redirection" "while verifying"
19782 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
19783 &_.forward_& files, as in the example above. There are two reasons for this:
19786 When Exim is receiving an incoming SMTP message from a remote host, it is
19787 running under the Exim uid, not as root. Exim is unable to change uid to read
19788 the file as the user, and it may not be able to read it as the Exim user. So in
19789 practice the router may not be able to operate.
19791 However, even when the router can operate, the existence of a &_.forward_& file
19792 is unimportant when verifying an address. What should be checked is whether the
19793 local part is a valid user name or not. Cutting out the redirection processing
19794 saves some resources.
19802 .section "Interpreting redirection data" "SECID126"
19803 .cindex "Sieve filter" "specifying in redirection data"
19804 .cindex "filter" "specifying in redirection data"
19805 The contents of the data string, whether obtained from &%data%& or &%file%&,
19806 can be interpreted in two different ways:
19809 If the &%allow_filter%& option is set true, and the data begins with the text
19810 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
19811 &'filtering'& instructions in the form of an Exim or Sieve filter file,
19812 respectively. Details of the syntax and semantics of filter files are described
19813 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
19814 document is intended for use by end users.
19816 Otherwise, the data must be a comma-separated list of redirection items, as
19817 described in the next section.
19820 When a message is redirected to a file (a &"mail folder"&), the file name given
19821 in a non-filter redirection list must always be an absolute path. A filter may
19822 generate a relative path &-- how this is handled depends on the transport's
19823 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
19824 for the &(appendfile)& transport.
19828 .section "Items in a non-filter redirection list" "SECTitenonfilred"
19829 .cindex "address redirection" "non-filter list items"
19830 When the redirection data is not an Exim or Sieve filter, for example, if it
19831 comes from a conventional alias or forward file, it consists of a list of
19832 addresses, file names, pipe commands, or certain special items (see section
19833 &<<SECTspecitredli>>& below). The special items can be individually enabled or
19834 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
19835 depending on their default values. The items in the list are separated by
19836 commas or newlines.
19837 If a comma is required in an item, the entire item must be enclosed in double
19840 Lines starting with a # character are comments, and are ignored, and # may
19841 also appear following a comma, in which case everything between the # and the
19842 next newline character is ignored.
19844 If an item is entirely enclosed in double quotes, these are removed. Otherwise
19845 double quotes are retained because some forms of mail address require their use
19846 (but never to enclose the entire address). In the following description,
19847 &"item"& refers to what remains after any surrounding double quotes have been
19850 .vindex "&$local_part$&"
19851 &*Warning*&: If you use an Exim expansion to construct a redirection address,
19852 and the expansion contains a reference to &$local_part$&, you should make use
19853 of the &%quote_local_part%& expansion operator, in case the local part contains
19854 special characters. For example, to redirect all mail for the domain
19855 &'obsolete.example'&, retaining the existing local part, you could use this
19858 data = ${quote_local_part:$local_part}@newdomain.example
19862 .section "Redirecting to a local mailbox" "SECTredlocmai"
19863 .cindex "routing" "loops in"
19864 .cindex "loop" "while routing, avoidance of"
19865 .cindex "address redirection" "to local mailbox"
19866 A redirection item may safely be the same as the address currently under
19867 consideration. This does not cause a routing loop, because a router is
19868 automatically skipped if any ancestor of the address that is being processed
19869 is the same as the current address and was processed by the current router.
19870 Such an address is therefore passed to the following routers, so it is handled
19871 as if there were no redirection. When making this loop-avoidance test, the
19872 complete local part, including any prefix or suffix, is used.
19874 .cindex "address redirection" "local part without domain"
19875 Specifying the same local part without a domain is a common usage in personal
19876 filter files when the user wants to have messages delivered to the local
19877 mailbox and also forwarded elsewhere. For example, the user whose login is
19878 &'cleo'& might have a &_.forward_& file containing this:
19880 cleo, cleopatra@egypt.example
19882 .cindex "backslash in alias file"
19883 .cindex "alias file" "backslash in"
19884 For compatibility with other MTAs, such unqualified local parts may be
19885 preceded by &"\"&, but this is not a requirement for loop prevention. However,
19886 it does make a difference if more than one domain is being handled
19889 If an item begins with &"\"& and the rest of the item parses as a valid RFC
19890 2822 address that does not include a domain, the item is qualified using the
19891 domain of the incoming address. In the absence of a leading &"\"&, unqualified
19892 addresses are qualified using the value in &%qualify_recipient%&, but you can
19893 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
19895 Care must be taken if there are alias names for local users.
19896 Consider an MTA handling a single local domain where the system alias file
19901 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
19902 messages in the local mailbox, and also forward copies elsewhere. He creates
19905 Sam.Reman, spqr@reme.elsewhere.example
19907 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
19908 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
19909 second time round, because it has previously routed it,
19910 and the following routers presumably cannot handle the alias. The forward file
19911 should really contain
19913 spqr, spqr@reme.elsewhere.example
19915 but because this is such a common error, the &%check_ancestor%& option (see
19916 below) exists to provide a way to get round it. This is normally set on a
19917 &(redirect)& router that is handling users' &_.forward_& files.
19921 .section "Special items in redirection lists" "SECTspecitredli"
19922 In addition to addresses, the following types of item may appear in redirection
19923 lists (that is, in non-filter redirection data):
19926 .cindex "pipe" "in redirection list"
19927 .cindex "address redirection" "to pipe"
19928 An item is treated as a pipe command if it begins with &"|"& and does not parse
19929 as a valid RFC 2822 address that includes a domain. A transport for running the
19930 command must be specified by the &%pipe_transport%& option.
19931 Normally, either the router or the transport specifies a user and a group under
19932 which to run the delivery. The default is to use the Exim user and group.
19934 Single or double quotes can be used for enclosing the individual arguments of
19935 the pipe command; no interpretation of escapes is done for single quotes. If
19936 the command contains a comma character, it is necessary to put the whole item
19937 in double quotes, for example:
19939 "|/some/command ready,steady,go"
19941 since items in redirection lists are terminated by commas. Do not, however,
19942 quote just the command. An item such as
19944 |"/some/command ready,steady,go"
19946 is interpreted as a pipe with a rather strange command name, and no arguments.
19948 Note that the above example assumes that the text comes from a lookup source
19949 of some sort, so that the quotes are part of the data. If composing a
19950 redirect router with a &%data%& option directly specifying this command, the
19951 quotes will be used by the configuration parser to define the extent of one
19952 string, but will not be passed down into the redirect router itself. There
19953 are two main approaches to get around this: escape quotes to be part of the
19954 data itself, or avoid using this mechanism and instead create a custom
19955 transport with the &%command%& option set and reference that transport from
19956 an &%accept%& router.
19959 .cindex "file" "in redirection list"
19960 .cindex "address redirection" "to file"
19961 An item is interpreted as a path name if it begins with &"/"& and does not
19962 parse as a valid RFC 2822 address that includes a domain. For example,
19964 /home/world/minbari
19966 is treated as a file name, but
19968 /s=molari/o=babylon/@x400gate.way
19970 is treated as an address. For a file name, a transport must be specified using
19971 the &%file_transport%& option. However, if the generated path name ends with a
19972 forward slash character, it is interpreted as a directory name rather than a
19973 file name, and &%directory_transport%& is used instead.
19975 Normally, either the router or the transport specifies a user and a group under
19976 which to run the delivery. The default is to use the Exim user and group.
19978 .cindex "&_/dev/null_&"
19979 However, if a redirection item is the path &_/dev/null_&, delivery to it is
19980 bypassed at a high level, and the log entry shows &"**bypassed**"&
19981 instead of a transport name. In this case the user and group are not used.
19984 .cindex "included address list"
19985 .cindex "address redirection" "included external list"
19986 If an item is of the form
19988 :include:<path name>
19990 a list of further items is taken from the given file and included at that
19991 point. &*Note*&: Such a file can not be a filter file; it is just an
19992 out-of-line addition to the list. The items in the included list are separated
19993 by commas or newlines and are not subject to expansion. If this is the first
19994 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
19995 the alias name. This example is incorrect:
19997 list1 :include:/opt/lists/list1
19999 It must be given as
20001 list1: :include:/opt/lists/list1
20004 .cindex "address redirection" "to black hole"
20005 .cindex "delivery" "discard"
20006 .cindex "delivery" "blackhole"
20007 .cindex "black hole"
20008 .cindex "abandoning mail"
20009 Sometimes you want to throw away mail to a particular local part. Making the
20010 &%data%& option expand to an empty string does not work, because that causes
20011 the router to decline. Instead, the alias item
20015 can be used. It does what its name implies. No delivery is
20016 done, and no error message is generated. This has the same effect as specifying
20017 &_/dev/null_& as a destination, but it can be independently disabled.
20019 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
20020 delivery is done for the original local part, even if other redirection items
20021 are present. If you are generating a multi-item list (for example, by reading a
20022 database) and need the ability to provide a no-op item, you must use
20026 .cindex "delivery" "forcing failure"
20027 .cindex "delivery" "forcing deferral"
20028 .cindex "failing delivery" "forcing"
20029 .cindex "deferred delivery, forcing"
20030 .cindex "customizing" "failure message"
20031 An attempt to deliver a particular address can be deferred or forced to fail by
20032 redirection items of the form
20037 respectively. When a redirection list contains such an item, it applies
20038 to the entire redirection; any other items in the list are ignored. Any
20039 text following &':fail:'& or &':defer:'& is placed in the error text
20040 associated with the failure. For example, an alias file might contain:
20042 X.Employee: :fail: Gone away, no forwarding address
20044 In the case of an address that is being verified from an ACL or as the subject
20046 .cindex "VRFY" "error text, display of"
20047 VRFY command, the text is included in the SMTP error response by
20049 .cindex "EXPN" "error text, display of"
20050 The text is not included in the response to an EXPN command. In non-SMTP cases
20051 the text is included in the error message that Exim generates.
20053 .cindex "SMTP" "error codes"
20054 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
20055 &':fail:'&. However, if the message starts with three digits followed by a
20056 space, optionally followed by an extended code of the form &'n.n.n'&, also
20057 followed by a space, and the very first digit is the same as the default error
20058 code, the code from the message is used instead. If the very first digit is
20059 incorrect, a panic error is logged, and the default code is used. You can
20060 suppress the use of the supplied code in a redirect router by setting the
20061 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
20064 .vindex "&$acl_verify_message$&"
20065 In an ACL, an explicitly provided message overrides the default, but the
20066 default message is available in the variable &$acl_verify_message$& and can
20067 therefore be included in a custom message if this is desired.
20069 Normally the error text is the rest of the redirection list &-- a comma does
20070 not terminate it &-- but a newline does act as a terminator. Newlines are not
20071 normally present in alias expansions. In &(lsearch)& lookups they are removed
20072 as part of the continuation process, but they may exist in other kinds of
20073 lookup and in &':include:'& files.
20075 During routing for message delivery (as opposed to verification), a redirection
20076 containing &':fail:'& causes an immediate failure of the incoming address,
20077 whereas &':defer:'& causes the message to remain on the queue so that a
20078 subsequent delivery attempt can happen at a later time. If an address is
20079 deferred for too long, it will ultimately fail, because the normal retry
20083 .cindex "alias file" "exception to default"
20084 Sometimes it is useful to use a single-key search type with a default (see
20085 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
20086 for exceptions to the default. These can be handled by aliasing them to
20087 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
20088 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
20089 results in an empty redirection list has the same effect.
20093 .section "Duplicate addresses" "SECTdupaddr"
20094 .cindex "duplicate addresses"
20095 .cindex "address duplicate, discarding"
20096 .cindex "pipe" "duplicated"
20097 Exim removes duplicate addresses from the list to which it is delivering, so as
20098 to deliver just one copy to each address. This does not apply to deliveries
20099 routed to pipes by different immediate parent addresses, but an indirect
20100 aliasing scheme of the type
20102 pipe: |/some/command $local_part
20106 does not work with a message that is addressed to both local parts, because
20107 when the second is aliased to the intermediate local part &"pipe"& it gets
20108 discarded as being the same as a previously handled address. However, a scheme
20111 localpart1: |/some/command $local_part
20112 localpart2: |/some/command $local_part
20114 does result in two different pipe deliveries, because the immediate parents of
20115 the pipes are distinct.
20119 .section "Repeated redirection expansion" "SECID128"
20120 .cindex "repeated redirection expansion"
20121 .cindex "address redirection" "repeated for each delivery attempt"
20122 When a message cannot be delivered to all of its recipients immediately,
20123 leading to two or more delivery attempts, redirection expansion is carried out
20124 afresh each time for those addresses whose children were not all previously
20125 delivered. If redirection is being used as a mailing list, this can lead to new
20126 members of the list receiving copies of old messages. The &%one_time%& option
20127 can be used to avoid this.
20130 .section "Errors in redirection lists" "SECID129"
20131 .cindex "address redirection" "errors"
20132 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
20133 error is skipped, and an entry is written to the main log. This may be useful
20134 for mailing lists that are automatically managed. Otherwise, if an error is
20135 detected while generating the list of new addresses, the original address is
20136 deferred. See also &%syntax_errors_to%&.
20140 .section "Private options for the redirect router" "SECID130"
20142 .cindex "options" "&(redirect)& router"
20143 The private options for the &(redirect)& router are as follows:
20146 .option allow_defer redirect boolean false
20147 Setting this option allows the use of &':defer:'& in non-filter redirection
20148 data, or the &%defer%& command in an Exim filter file.
20151 .option allow_fail redirect boolean false
20152 .cindex "failing delivery" "from filter"
20153 If this option is true, the &':fail:'& item can be used in a redirection list,
20154 and the &%fail%& command may be used in an Exim filter file.
20157 .option allow_filter redirect boolean false
20158 .cindex "filter" "enabling use of"
20159 .cindex "Sieve filter" "enabling use of"
20160 Setting this option allows Exim to interpret redirection data that starts with
20161 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
20162 are some features of Exim filter files that some administrators may wish to
20163 lock out; see the &%forbid_filter_%&&'xxx'& options below.
20165 It is also possible to lock out Exim filters or Sieve filters while allowing
20166 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
20169 The filter is run using the uid and gid set by the generic &%user%& and
20170 &%group%& options. These take their defaults from the password data if
20171 &%check_local_user%& is set, so in the normal case of users' personal filter
20172 files, the filter is run as the relevant user. When &%allow_filter%& is set
20173 true, Exim insists that either &%check_local_user%& or &%user%& is set.
20177 .option allow_freeze redirect boolean false
20178 .cindex "freezing messages" "allowing in filter"
20179 Setting this option allows the use of the &%freeze%& command in an Exim filter.
20180 This command is more normally encountered in system filters, and is disabled by
20181 default for redirection filters because it isn't something you usually want to
20182 let ordinary users do.
20186 .option check_ancestor redirect boolean false
20187 This option is concerned with handling generated addresses that are the same
20188 as some address in the list of redirection ancestors of the current address.
20189 Although it is turned off by default in the code, it is set in the default
20190 configuration file for handling users' &_.forward_& files. It is recommended
20191 for this use of the &(redirect)& router.
20193 When &%check_ancestor%& is set, if a generated address (including the domain)
20194 is the same as any ancestor of the current address, it is replaced by a copy of
20195 the current address. This helps in the case where local part A is aliased to B,
20196 and B has a &_.forward_& file pointing back to A. For example, within a single
20197 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
20198 &_&~jb/.forward_& contains:
20200 \Joe.Bloggs, <other item(s)>
20202 Without the &%check_ancestor%& setting, either local part (&"jb"& or
20203 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
20204 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
20205 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
20206 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
20207 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
20208 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
20209 original address. See also the &%repeat_use%& option below.
20212 .option check_group redirect boolean "see below"
20213 When the &%file%& option is used, the group owner of the file is checked only
20214 when this option is set. The permitted groups are those listed in the
20215 &%owngroups%& option, together with the user's default group if
20216 &%check_local_user%& is set. If the file has the wrong group, routing is
20217 deferred. The default setting for this option is true if &%check_local_user%&
20218 is set and the &%modemask%& option permits the group write bit, or if the
20219 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
20223 .option check_owner redirect boolean "see below"
20224 When the &%file%& option is used, the owner of the file is checked only when
20225 this option is set. If &%check_local_user%& is set, the local user is
20226 permitted; otherwise the owner must be one of those listed in the &%owners%&
20227 option. The default value for this option is true if &%check_local_user%& or
20228 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20231 .option data redirect string&!! unset
20232 This option is mutually exclusive with &%file%&. One or other of them must be
20233 set, but not both. The contents of &%data%& are expanded, and then used as the
20234 list of forwarding items, or as a set of filtering instructions. If the
20235 expansion is forced to fail, or the result is an empty string or a string that
20236 has no effect (consists entirely of comments), the router declines.
20238 When filtering instructions are used, the string must begin with &"#Exim
20239 filter"&, and all comments in the string, including this initial one, must be
20240 terminated with newline characters. For example:
20242 data = #Exim filter\n\
20243 if $h_to: contains Exim then save $home/mail/exim endif
20245 If you are reading the data from a database where newlines cannot be included,
20246 you can use the &${sg}$& expansion item to turn the escape string of your
20247 choice into a newline.
20250 .option directory_transport redirect string&!! unset
20251 A &(redirect)& router sets up a direct delivery to a directory when a path name
20252 ending with a slash is specified as a new &"address"&. The transport used is
20253 specified by this option, which, after expansion, must be the name of a
20254 configured transport. This should normally be an &(appendfile)& transport.
20257 .option file redirect string&!! unset
20258 This option specifies the name of a file that contains the redirection data. It
20259 is mutually exclusive with the &%data%& option. The string is expanded before
20260 use; if the expansion is forced to fail, the router declines. Other expansion
20261 failures cause delivery to be deferred. The result of a successful expansion
20262 must be an absolute path. The entire file is read and used as the redirection
20263 data. If the data is an empty string or a string that has no effect (consists
20264 entirely of comments), the router declines.
20266 .cindex "NFS" "checking for file existence"
20267 If the attempt to open the file fails with a &"does not exist"& error, Exim
20268 runs a check on the containing directory,
20269 unless &%ignore_enotdir%& is true (see below).
20270 If the directory does not appear to exist, delivery is deferred. This can
20271 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20272 is a mount problem. If the containing directory does exist, but the file does
20273 not, the router declines.
20276 .option file_transport redirect string&!! unset
20277 .vindex "&$address_file$&"
20278 A &(redirect)& router sets up a direct delivery to a file when a path name not
20279 ending in a slash is specified as a new &"address"&. The transport used is
20280 specified by this option, which, after expansion, must be the name of a
20281 configured transport. This should normally be an &(appendfile)& transport. When
20282 it is running, the file name is in &$address_file$&.
20285 .option filter_prepend_home redirect boolean true
20286 When this option is true, if a &(save)& command in an Exim filter specifies a
20287 relative path, and &$home$& is defined, it is automatically prepended to the
20288 relative path. If this option is set false, this action does not happen. The
20289 relative path is then passed to the transport unmodified.
20292 .option forbid_blackhole redirect boolean false
20293 If this option is true, the &':blackhole:'& item may not appear in a
20297 .option forbid_exim_filter redirect boolean false
20298 If this option is set true, only Sieve filters are permitted when
20299 &%allow_filter%& is true.
20304 .option forbid_file redirect boolean false
20305 .cindex "delivery" "to file; forbidding"
20306 .cindex "Sieve filter" "forbidding delivery to a file"
20307 .cindex "Sieve filter" "&""keep""& facility; disabling"
20308 If this option is true, this router may not generate a new address that
20309 specifies delivery to a local file or directory, either from a filter or from a
20310 conventional forward file. This option is forced to be true if &%one_time%& is
20311 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20312 locks out the Sieve's &"keep"& facility.
20315 .option forbid_filter_dlfunc redirect boolean false
20316 .cindex "filter" "locking out certain features"
20317 If this option is true, string expansions in Exim filters are not allowed to
20318 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20321 .option forbid_filter_existstest redirect boolean false
20322 .cindex "expansion" "statting a file"
20323 If this option is true, string expansions in Exim filters are not allowed to
20324 make use of the &%exists%& condition or the &%stat%& expansion item.
20326 .option forbid_filter_logwrite redirect boolean false
20327 If this option is true, use of the logging facility in Exim filters is not
20328 permitted. Logging is in any case available only if the filter is being run
20329 under some unprivileged uid (which is normally the case for ordinary users'
20330 &_.forward_& files).
20333 .option forbid_filter_lookup redirect boolean false
20334 If this option is true, string expansions in Exim filter files are not allowed
20335 to make use of &%lookup%& items.
20338 .option forbid_filter_perl redirect boolean false
20339 This option has an effect only if Exim is built with embedded Perl support. If
20340 it is true, string expansions in Exim filter files are not allowed to make use
20341 of the embedded Perl support.
20344 .option forbid_filter_readfile redirect boolean false
20345 If this option is true, string expansions in Exim filter files are not allowed
20346 to make use of &%readfile%& items.
20349 .option forbid_filter_readsocket redirect boolean false
20350 If this option is true, string expansions in Exim filter files are not allowed
20351 to make use of &%readsocket%& items.
20354 .option forbid_filter_reply redirect boolean false
20355 If this option is true, this router may not generate an automatic reply
20356 message. Automatic replies can be generated only from Exim or Sieve filter
20357 files, not from traditional forward files. This option is forced to be true if
20358 &%one_time%& is set.
20361 .option forbid_filter_run redirect boolean false
20362 If this option is true, string expansions in Exim filter files are not allowed
20363 to make use of &%run%& items.
20366 .option forbid_include redirect boolean false
20367 If this option is true, items of the form
20369 :include:<path name>
20371 are not permitted in non-filter redirection lists.
20374 .option forbid_pipe redirect boolean false
20375 .cindex "delivery" "to pipe; forbidding"
20376 If this option is true, this router may not generate a new address which
20377 specifies delivery to a pipe, either from an Exim filter or from a conventional
20378 forward file. This option is forced to be true if &%one_time%& is set.
20381 .option forbid_sieve_filter redirect boolean false
20382 If this option is set true, only Exim filters are permitted when
20383 &%allow_filter%& is true.
20386 .cindex "SMTP" "error codes"
20387 .option forbid_smtp_code redirect boolean false
20388 If this option is set true, any SMTP error codes that are present at the start
20389 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20390 the default codes (451 and 550, respectively) are always used.
20395 .option hide_child_in_errmsg redirect boolean false
20396 .cindex "bounce message" "redirection details; suppressing"
20397 If this option is true, it prevents Exim from quoting a child address if it
20398 generates a bounce or delay message for it. Instead it says &"an address
20399 generated from <&'the top level address'&>"&. Of course, this applies only to
20400 bounces generated locally. If a message is forwarded to another host, &'its'&
20401 bounce may well quote the generated address.
20404 .option ignore_eacces redirect boolean false
20406 If this option is set and an attempt to open a redirection file yields the
20407 EACCES error (permission denied), the &(redirect)& router behaves as if the
20408 file did not exist.
20411 .option ignore_enotdir redirect boolean false
20413 If this option is set and an attempt to open a redirection file yields the
20414 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20415 router behaves as if the file did not exist.
20417 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20418 router that has the &%file%& option set discovers that the file does not exist
20419 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20420 against unmounted NFS directories. If the parent can not be statted, delivery
20421 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20422 is set, because that option tells Exim to ignore &"something on the path is not
20423 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20424 that some operating systems give ENOENT where others give ENOTDIR.
20428 .option include_directory redirect string unset
20429 If this option is set, the path names of any &':include:'& items in a
20430 redirection list must start with this directory.
20433 .option modemask redirect "octal integer" 022
20434 This specifies mode bits which must not be set for a file specified by the
20435 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20438 .option one_time redirect boolean false
20439 .cindex "one-time aliasing/forwarding expansion"
20440 .cindex "alias file" "one-time expansion"
20441 .cindex "forward file" "one-time expansion"
20442 .cindex "mailing lists" "one-time expansion"
20443 .cindex "address redirection" "one-time expansion"
20444 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20445 files each time it tries to deliver a message causes a problem when one or more
20446 of the generated addresses fails be delivered at the first attempt. The problem
20447 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20448 but of what happens when the redirection list changes during the time that the
20449 message is on Exim's queue. This is particularly true in the case of mailing
20450 lists, where new subscribers might receive copies of messages that were posted
20451 before they subscribed.
20453 If &%one_time%& is set and any addresses generated by the router fail to
20454 deliver at the first attempt, the failing addresses are added to the message as
20455 &"top level"& addresses, and the parent address that generated them is marked
20456 &"delivered"&. Thus, redirection does not happen again at the next delivery
20459 &*Warning 1*&: Any header line addition or removal that is specified by this
20460 router would be lost if delivery did not succeed at the first attempt. For this
20461 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20462 permitted when &%one_time%& is set.
20464 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20465 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20466 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20468 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20471 The original top-level address is remembered with each of the generated
20472 addresses, and is output in any log messages. However, any intermediate parent
20473 addresses are not recorded. This makes a difference to the log only if
20474 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20475 typically be used for mailing lists, where there is normally just one level of
20479 .option owners redirect "string list" unset
20480 .cindex "ownership" "alias file"
20481 .cindex "ownership" "forward file"
20482 .cindex "alias file" "ownership"
20483 .cindex "forward file" "ownership"
20484 This specifies a list of permitted owners for the file specified by &%file%&.
20485 This list is in addition to the local user when &%check_local_user%& is set.
20486 See &%check_owner%& above.
20489 .option owngroups redirect "string list" unset
20490 This specifies a list of permitted groups for the file specified by &%file%&.
20491 The list is in addition to the local user's primary group when
20492 &%check_local_user%& is set. See &%check_group%& above.
20495 .option pipe_transport redirect string&!! unset
20496 .vindex "&$address_pipe$&"
20497 A &(redirect)& router sets up a direct delivery to a pipe when a string
20498 starting with a vertical bar character is specified as a new &"address"&. The
20499 transport used is specified by this option, which, after expansion, must be the
20500 name of a configured transport. This should normally be a &(pipe)& transport.
20501 When the transport is run, the pipe command is in &$address_pipe$&.
20504 .option qualify_domain redirect string&!! unset
20505 .vindex "&$qualify_recipient$&"
20506 If this option is set, and an unqualified address (one without a domain) is
20507 generated, and that address would normally be qualified by the global setting
20508 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20509 expanding this string. If the expansion fails, the router declines. If you want
20510 to revert to the default, you can have the expansion generate
20511 &$qualify_recipient$&.
20513 This option applies to all unqualified addresses generated by Exim filters,
20514 but for traditional &_.forward_& files, it applies only to addresses that are
20515 not preceded by a backslash. Sieve filters cannot generate unqualified
20518 .option qualify_preserve_domain redirect boolean false
20519 .cindex "domain" "in redirection; preserving"
20520 .cindex "preserving domain in redirection"
20521 .cindex "address redirection" "domain; preserving"
20522 If this option is set, the router's local &%qualify_domain%& option must not be
20523 set (a configuration error occurs if it is). If an unqualified address (one
20524 without a domain) is generated, it is qualified with the domain of the parent
20525 address (the immediately preceding ancestor) instead of the global
20526 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20527 this applies whether or not the address is preceded by a backslash.
20530 .option repeat_use redirect boolean true
20531 If this option is set false, the router is skipped for a child address that has
20532 any ancestor that was routed by this router. This test happens before any of
20533 the other preconditions are tested. Exim's default anti-looping rules skip
20534 only when the ancestor is the same as the current address. See also
20535 &%check_ancestor%& above and the generic &%redirect_router%& option.
20538 .option reply_transport redirect string&!! unset
20539 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20540 &%vacation%& command is used in a filter file. The transport used is specified
20541 by this option, which, after expansion, must be the name of a configured
20542 transport. This should normally be an &(autoreply)& transport. Other transports
20543 are unlikely to do anything sensible or useful.
20546 .option rewrite redirect boolean true
20547 .cindex "address redirection" "disabling rewriting"
20548 If this option is set false, addresses generated by the router are not
20549 subject to address rewriting. Otherwise, they are treated like new addresses
20550 and are rewritten according to the global rewriting rules.
20553 .option sieve_subaddress redirect string&!! unset
20554 The value of this option is passed to a Sieve filter to specify the
20555 :subaddress part of an address.
20557 .option sieve_useraddress redirect string&!! unset
20558 The value of this option is passed to a Sieve filter to specify the :user part
20559 of an address. However, if it is unset, the entire original local part
20560 (including any prefix or suffix) is used for :user.
20563 .option sieve_vacation_directory redirect string&!! unset
20564 .cindex "Sieve filter" "vacation directory"
20565 To enable the &"vacation"& extension for Sieve filters, you must set
20566 &%sieve_vacation_directory%& to the directory where vacation databases are held
20567 (do not put anything else in that directory), and ensure that the
20568 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20569 needs their own directory; Exim will create it if necessary.
20573 .option skip_syntax_errors redirect boolean false
20574 .cindex "forward file" "broken"
20575 .cindex "address redirection" "broken files"
20576 .cindex "alias file" "broken"
20577 .cindex "broken alias or forward files"
20578 .cindex "ignoring faulty addresses"
20579 .cindex "skipping faulty addresses"
20580 .cindex "error" "skipping bad syntax"
20581 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20582 non-filter redirection data are skipped, and each failing address is logged. If
20583 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20584 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20585 are expanded and placed at the head of the error message generated by
20586 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20587 be the same address as the generic &%errors_to%& option. The
20588 &%skip_syntax_errors%& option is often used when handling mailing lists.
20590 If all the addresses in a redirection list are skipped because of syntax
20591 errors, the router declines to handle the original address, and it is passed to
20592 the following routers.
20594 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20595 error in the filter causes filtering to be abandoned without any action being
20596 taken. The incident is logged, and the router declines to handle the address,
20597 so it is passed to the following routers.
20599 .cindex "Sieve filter" "syntax errors in"
20600 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20601 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20602 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20604 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20605 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20606 option, used with an address that does not get redirected, can be used to
20607 notify users of these errors, by means of a router like this:
20613 file = $home/.forward
20614 file_transport = address_file
20615 pipe_transport = address_pipe
20616 reply_transport = address_reply
20619 syntax_errors_to = real-$local_part@$domain
20620 syntax_errors_text = \
20621 This is an automatically generated message. An error has\n\
20622 been found in your .forward file. Details of the error are\n\
20623 reported below. While this error persists, you will receive\n\
20624 a copy of this message for every message that is addressed\n\
20625 to you. If your .forward file is a filter file, or if it is\n\
20626 a non-filter file containing no valid forwarding addresses,\n\
20627 a copy of each incoming message will be put in your normal\n\
20628 mailbox. If a non-filter file contains at least one valid\n\
20629 forwarding address, forwarding to the valid addresses will\n\
20630 happen, and those will be the only deliveries that occur.
20632 You also need a router to ensure that local addresses that are prefixed by
20633 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20634 put this immediately before the &(userforward)& router:
20639 local_part_prefix = real-
20640 transport = local_delivery
20642 For security, it would probably be a good idea to restrict the use of this
20643 router to locally-generated messages, using a condition such as this:
20645 condition = ${if match {$sender_host_address}\
20646 {\N^(|127\.0\.0\.1)$\N}}
20650 .option syntax_errors_text redirect string&!! unset
20651 See &%skip_syntax_errors%& above.
20654 .option syntax_errors_to redirect string unset
20655 See &%skip_syntax_errors%& above.
20656 .ecindex IIDredrou1
20657 .ecindex IIDredrou2
20664 . ////////////////////////////////////////////////////////////////////////////
20665 . ////////////////////////////////////////////////////////////////////////////
20667 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20668 "Environment for local transports"
20669 .scindex IIDenvlotra1 "local transports" "environment for"
20670 .scindex IIDenvlotra2 "environment" "local transports"
20671 .scindex IIDenvlotra3 "transport" "local; environment for"
20672 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20673 transport can be thought of as similar to a pipe.) Exim always runs transports
20674 in subprocesses, under specified uids and gids. Typical deliveries to local
20675 mailboxes run under the uid and gid of the local user.
20677 Exim also sets a specific current directory while running the transport; for
20678 some transports a home directory setting is also relevant. The &(pipe)&
20679 transport is the only one that sets up environment variables; see section
20680 &<<SECTpipeenv>>& for details.
20682 The values used for the uid, gid, and the directories may come from several
20683 different places. In many cases, the router that handles the address associates
20684 settings with that address as a result of its &%check_local_user%&, &%group%&,
20685 or &%user%& options. However, values may also be given in the transport's own
20686 configuration, and these override anything that comes from the router.
20690 .section "Concurrent deliveries" "SECID131"
20691 .cindex "concurrent deliveries"
20692 .cindex "simultaneous deliveries"
20693 If two different messages for the same local recipient arrive more or less
20694 simultaneously, the two delivery processes are likely to run concurrently. When
20695 the &(appendfile)& transport is used to write to a file, Exim applies locking
20696 rules to stop concurrent processes from writing to the same file at the same
20699 However, when you use a &(pipe)& transport, it is up to you to arrange any
20700 locking that is needed. Here is a silly example:
20704 command = /bin/sh -c 'cat >>/some/file'
20706 This is supposed to write the message at the end of the file. However, if two
20707 messages arrive at the same time, the file will be scrambled. You can use the
20708 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20709 file using the same algorithm that Exim itself uses.
20714 .section "Uids and gids" "SECTenvuidgid"
20715 .cindex "local transports" "uid and gid"
20716 .cindex "transport" "local; uid and gid"
20717 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20718 overrides any group that the router set in the address, even if &%user%& is not
20719 set for the transport. This makes it possible, for example, to run local mail
20720 delivery under the uid of the recipient (set by the router), but in a special
20721 group (set by the transport). For example:
20724 # User/group are set by check_local_user in this router
20728 transport = group_delivery
20731 # This transport overrides the group
20733 driver = appendfile
20734 file = /var/spool/mail/$local_part
20737 If &%user%& is set for a transport, its value overrides what is set in the
20738 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
20739 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
20742 .oindex "&%initgroups%&"
20743 When the uid is taken from the transport's configuration, the &[initgroups()]&
20744 function is called for the groups associated with that uid if the
20745 &%initgroups%& option is set for the transport. When the uid is not specified
20746 by the transport, but is associated with the address by a router, the option
20747 for calling &[initgroups()]& is taken from the router configuration.
20749 .cindex "&(pipe)& transport" "uid for"
20750 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
20751 is set and &%user%& is not set, the uid of the process that called Exim to
20752 receive the message is used, and if &%group%& is not set, the corresponding
20753 original gid is also used.
20755 This is the detailed preference order for obtaining a gid; the first of the
20756 following that is set is used:
20759 A &%group%& setting of the transport;
20761 A &%group%& setting of the router;
20763 A gid associated with a user setting of the router, either as a result of
20764 &%check_local_user%& or an explicit non-numeric &%user%& setting;
20766 The group associated with a non-numeric &%user%& setting of the transport;
20768 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
20769 the uid is the creator's uid;
20771 The Exim gid if the Exim uid is being used as a default.
20774 If, for example, the user is specified numerically on the router and there are
20775 no group settings, no gid is available. In this situation, an error occurs.
20776 This is different for the uid, for which there always is an ultimate default.
20777 The first of the following that is set is used:
20780 A &%user%& setting of the transport;
20782 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
20784 A &%user%& setting of the router;
20786 A &%check_local_user%& setting of the router;
20791 Of course, an error will still occur if the uid that is chosen is on the
20792 &%never_users%& list.
20798 .section "Current and home directories" "SECID132"
20799 .cindex "current directory for local transport"
20800 .cindex "home directory" "for local transport"
20801 .cindex "transport" "local; home directory for"
20802 .cindex "transport" "local; current directory for"
20803 Routers may set current and home directories for local transports by means of
20804 the &%transport_current_directory%& and &%transport_home_directory%& options.
20805 However, if the transport's &%current_directory%& or &%home_directory%& options
20806 are set, they override the router's values. In detail, the home directory
20807 for a local transport is taken from the first of these values that is set:
20810 The &%home_directory%& option on the transport;
20812 The &%transport_home_directory%& option on the router;
20814 The password data if &%check_local_user%& is set on the router;
20816 The &%router_home_directory%& option on the router.
20819 The current directory is taken from the first of these values that is set:
20822 The &%current_directory%& option on the transport;
20824 The &%transport_current_directory%& option on the router.
20828 If neither the router nor the transport sets a current directory, Exim uses the
20829 value of the home directory, if it is set. Otherwise it sets the current
20830 directory to &_/_& before running a local transport.
20834 .section "Expansion variables derived from the address" "SECID133"
20835 .vindex "&$domain$&"
20836 .vindex "&$local_part$&"
20837 .vindex "&$original_domain$&"
20838 Normally a local delivery is handling a single address, and in that case the
20839 variables such as &$domain$& and &$local_part$& are set during local
20840 deliveries. However, in some circumstances more than one address may be handled
20841 at once (for example, while writing batch SMTP for onward transmission by some
20842 other means). In this case, the variables associated with the local part are
20843 never set, &$domain$& is set only if all the addresses have the same domain,
20844 and &$original_domain$& is never set.
20845 .ecindex IIDenvlotra1
20846 .ecindex IIDenvlotra2
20847 .ecindex IIDenvlotra3
20855 . ////////////////////////////////////////////////////////////////////////////
20856 . ////////////////////////////////////////////////////////////////////////////
20858 .chapter "Generic options for transports" "CHAPtransportgeneric"
20859 .scindex IIDgenoptra1 "generic options" "transport"
20860 .scindex IIDgenoptra2 "options" "generic; for transports"
20861 .scindex IIDgenoptra3 "transport" "generic options for"
20862 The following generic options apply to all transports:
20865 .option body_only transports boolean false
20866 .cindex "transport" "body only"
20867 .cindex "message" "transporting body only"
20868 .cindex "body of message" "transporting"
20869 If this option is set, the message's headers are not transported. It is
20870 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
20871 or &(pipe)& transports, the settings of &%message_prefix%& and
20872 &%message_suffix%& should be checked, because this option does not
20873 automatically suppress them.
20876 .option current_directory transports string&!! unset
20877 .cindex "transport" "current directory for"
20878 This specifies the current directory that is to be set while running the
20879 transport, overriding any value that may have been set by the router.
20880 If the expansion fails for any reason, including forced failure, an error is
20881 logged, and delivery is deferred.
20884 .option disable_logging transports boolean false
20885 If this option is set true, nothing is logged for any
20886 deliveries by the transport or for any
20887 transport errors. You should not set this option unless you really, really know
20888 what you are doing.
20891 .option debug_print transports string&!! unset
20892 .cindex "testing" "variables in drivers"
20893 If this option is set and debugging is enabled (see the &%-d%& command line
20894 option), the string is expanded and included in the debugging output when the
20896 If expansion of the string fails, the error message is written to the debugging
20897 output, and Exim carries on processing.
20898 This facility is provided to help with checking out the values of variables and
20899 so on when debugging driver configurations. For example, if a &%headers_add%&
20900 option is not working properly, &%debug_print%& could be used to output the
20901 variables it references. A newline is added to the text if it does not end with
20903 The variables &$transport_name$& and &$router_name$& contain the name of the
20904 transport and the router that called it.
20906 .option delivery_date_add transports boolean false
20907 .cindex "&'Delivery-date:'& header line"
20908 If this option is true, a &'Delivery-date:'& header is added to the message.
20909 This gives the actual time the delivery was made. As this is not a standard
20910 header, Exim has a configuration option (&%delivery_date_remove%&) which
20911 requests its removal from incoming messages, so that delivered messages can
20912 safely be resent to other recipients.
20915 .option driver transports string unset
20916 This specifies which of the available transport drivers is to be used.
20917 There is no default, and this option must be set for every transport.
20920 .option envelope_to_add transports boolean false
20921 .cindex "&'Envelope-to:'& header line"
20922 If this option is true, an &'Envelope-to:'& header is added to the message.
20923 This gives the original address(es) in the incoming envelope that caused this
20924 delivery to happen. More than one address may be present if the transport is
20925 configured to handle several addresses at once, or if more than one original
20926 address was redirected to the same final address. As this is not a standard
20927 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
20928 its removal from incoming messages, so that delivered messages can safely be
20929 resent to other recipients.
20932 .option event_action transports string&!! unset
20934 This option declares a string to be expanded for Exim's events mechanism.
20935 For details see chapter &<<CHAPevents>>&.
20938 .option group transports string&!! "Exim group"
20939 .cindex "transport" "group; specifying"
20940 This option specifies a gid for running the transport process, overriding any
20941 value that the router supplies, and also overriding any value associated with
20942 &%user%& (see below).
20945 .option headers_add transports list&!! unset
20946 .cindex "header lines" "adding in transport"
20947 .cindex "transport" "header lines; adding"
20948 This option specifies a list of text headers,
20949 newline-separated (by default, changeable in the usual way),
20950 which are (separately) expanded and added to the header
20951 portion of a message as it is transported, as described in section
20952 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
20953 routers. If the result of the expansion is an empty string, or if the expansion
20954 is forced to fail, no action is taken. Other expansion failures are treated as
20955 errors and cause the delivery to be deferred.
20957 Unlike most options, &%headers_add%& can be specified multiple times
20958 for a transport; all listed headers are added.
20961 .option headers_only transports boolean false
20962 .cindex "transport" "header lines only"
20963 .cindex "message" "transporting headers only"
20964 .cindex "header lines" "transporting"
20965 If this option is set, the message's body is not transported. It is mutually
20966 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
20967 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
20968 checked, since this option does not automatically suppress them.
20971 .option headers_remove transports list&!! unset
20972 .cindex "header lines" "removing"
20973 .cindex "transport" "header lines; removing"
20974 This option specifies a list of header names,
20975 colon-separated (by default, changeable in the usual way);
20976 these headers are omitted from the message as it is transported, as described
20977 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
20979 Each list item is separately expanded.
20980 If the result of the expansion is an empty string, or if the expansion
20981 is forced to fail, no action is taken. Other expansion failures are treated as
20982 errors and cause the delivery to be deferred.
20984 Unlike most options, &%headers_remove%& can be specified multiple times
20985 for a transport; all listed headers are removed.
20987 &*Warning*&: Because of the separate expansion of the list items,
20988 items that contain a list separator must have it doubled.
20989 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
20993 .option headers_rewrite transports string unset
20994 .cindex "transport" "header lines; rewriting"
20995 .cindex "rewriting" "at transport time"
20996 This option allows addresses in header lines to be rewritten at transport time,
20997 that is, as the message is being copied to its destination. The contents of the
20998 option are a colon-separated list of rewriting rules. Each rule is in exactly
20999 the same form as one of the general rewriting rules that are applied when a
21000 message is received. These are described in chapter &<<CHAPrewrite>>&. For
21003 headers_rewrite = a@b c@d f : \
21006 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
21007 &'w@z'& in all address-bearing header lines. The rules are applied to the
21008 header lines just before they are written out at transport time, so they affect
21009 only those copies of the message that pass through the transport. However, only
21010 the message's original header lines, and any that were added by a system
21011 filter, are rewritten. If a router or transport adds header lines, they are not
21012 affected by this option. These rewriting rules are &'not'& applied to the
21013 envelope. You can change the return path using &%return_path%&, but you cannot
21014 change envelope recipients at this time.
21017 .option home_directory transports string&!! unset
21018 .cindex "transport" "home directory for"
21020 This option specifies a home directory setting for a local transport,
21021 overriding any value that may be set by the router. The home directory is
21022 placed in &$home$& while expanding the transport's private options. It is also
21023 used as the current directory if no current directory is set by the
21024 &%current_directory%& option on the transport or the
21025 &%transport_current_directory%& option on the router. If the expansion fails
21026 for any reason, including forced failure, an error is logged, and delivery is
21030 .option initgroups transports boolean false
21031 .cindex "additional groups"
21032 .cindex "groups" "additional"
21033 .cindex "transport" "group; additional"
21034 If this option is true and the uid for the delivery process is provided by the
21035 transport, the &[initgroups()]& function is called when running the transport
21036 to ensure that any additional groups associated with the uid are set up.
21039 .option max_parallel transports integer&!! unset
21040 .cindex limit "transport parallelism"
21041 .cindex transport "parallel processes"
21042 .cindex transport "concurrency limit"
21043 .cindex "delivery" "parallelism for transport"
21044 If this option is set and expands to an integer greater than zero
21045 it limits the number of concurrent runs of the transport.
21046 The control does not apply to shadow transports.
21048 .cindex "hints database" "transport concurrency control"
21049 Exim implements this control by means of a hints database in which a record is
21050 incremented whenever a transport process is being created. The record
21051 is decremented and possibly removed when the process terminates.
21052 Obviously there is scope for
21053 records to get left lying around if there is a system or program crash. To
21054 guard against this, Exim ignores any records that are more than six hours old.
21056 If you use this option, you should also arrange to delete the
21057 relevant hints database whenever your system reboots. The names of the files
21058 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21059 may be one or two files, depending on the type of DBM in use. The same files
21060 are used for ETRN and smtp transport serialization.
21063 .option message_size_limit transports string&!! 0
21064 .cindex "limit" "message size per transport"
21065 .cindex "size" "of message, limit"
21066 .cindex "transport" "message size; limiting"
21067 This option controls the size of messages passed through the transport. It is
21068 expanded before use; the result of the expansion must be a sequence of decimal
21069 digits, optionally followed by K or M. If the expansion fails for any reason,
21070 including forced failure, or if the result is not of the required form,
21071 delivery is deferred. If the value is greater than zero and the size of a
21072 message exceeds this limit, the address is failed. If there is any chance that
21073 the resulting bounce message could be routed to the same transport, you should
21074 ensure that &%return_size_limit%& is less than the transport's
21075 &%message_size_limit%&, as otherwise the bounce message will fail to get
21080 .option rcpt_include_affixes transports boolean false
21081 .cindex "prefix" "for local part, including in envelope"
21082 .cindex "suffix for local part" "including in envelope"
21083 .cindex "local part" "prefix"
21084 .cindex "local part" "suffix"
21085 When this option is false (the default), and an address that has had any
21086 affixes (prefixes or suffixes) removed from the local part is delivered by any
21087 form of SMTP or LMTP, the affixes are not included. For example, if a router
21090 local_part_prefix = *-
21092 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
21095 RCPT TO:<xyz@some.domain>
21097 This is also the case when an ACL-time callout is being used to verify a
21098 recipient address. However, if &%rcpt_include_affixes%& is set true, the
21099 whole local part is included in the RCPT command. This option applies to BSMTP
21100 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
21101 &(lmtp)& and &(smtp)& transports.
21104 .option retry_use_local_part transports boolean "see below"
21105 .cindex "hints database" "retry keys"
21106 When a delivery suffers a temporary failure, a retry record is created
21107 in Exim's hints database. For remote deliveries, the key for the retry record
21108 is based on the name and/or IP address of the failing remote host. For local
21109 deliveries, the key is normally the entire address, including both the local
21110 part and the domain. This is suitable for most common cases of local delivery
21111 temporary failure &-- for example, exceeding a mailbox quota should delay only
21112 deliveries to that mailbox, not to the whole domain.
21114 However, in some special cases you may want to treat a temporary local delivery
21115 as a failure associated with the domain, and not with a particular local part.
21116 (For example, if you are storing all mail for some domain in files.) You can do
21117 this by setting &%retry_use_local_part%& false.
21119 For all the local transports, its default value is true. For remote transports,
21120 the default value is false for tidiness, but changing the value has no effect
21121 on a remote transport in the current implementation.
21124 .option return_path transports string&!! unset
21125 .cindex "envelope sender"
21126 .cindex "transport" "return path; changing"
21127 .cindex "return path" "changing in transport"
21128 If this option is set, the string is expanded at transport time and replaces
21129 the existing return path (envelope sender) value in the copy of the message
21130 that is being delivered. An empty return path is permitted. This feature is
21131 designed for remote deliveries, where the value of this option is used in the
21132 SMTP MAIL command. If you set &%return_path%& for a local transport, the
21133 only effect is to change the address that is placed in the &'Return-path:'&
21134 header line, if one is added to the message (see the next option).
21136 &*Note:*& A changed return path is not logged unless you add
21137 &%return_path_on_delivery%& to the log selector.
21139 .vindex "&$return_path$&"
21140 The expansion can refer to the existing value via &$return_path$&. This is
21141 either the message's envelope sender, or an address set by the
21142 &%errors_to%& option on a router. If the expansion is forced to fail, no
21143 replacement occurs; if it fails for another reason, delivery is deferred. This
21144 option can be used to support VERP (Variable Envelope Return Paths) &-- see
21145 section &<<SECTverp>>&.
21147 &*Note*&: If a delivery error is detected locally, including the case when a
21148 remote server rejects a message at SMTP time, the bounce message is not sent to
21149 the value of this option. It is sent to the previously set errors address.
21150 This defaults to the incoming sender address, but can be changed by setting
21151 &%errors_to%& in a router.
21155 .option return_path_add transports boolean false
21156 .cindex "&'Return-path:'& header line"
21157 If this option is true, a &'Return-path:'& header is added to the message.
21158 Although the return path is normally available in the prefix line of BSD
21159 mailboxes, this is commonly not displayed by MUAs, and so the user does not
21160 have easy access to it.
21162 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
21163 the delivery SMTP server makes the final delivery"&. This implies that this
21164 header should not be present in incoming messages. Exim has a configuration
21165 option, &%return_path_remove%&, which requests removal of this header from
21166 incoming messages, so that delivered messages can safely be resent to other
21170 .option shadow_condition transports string&!! unset
21171 See &%shadow_transport%& below.
21174 .option shadow_transport transports string unset
21175 .cindex "shadow transport"
21176 .cindex "transport" "shadow"
21177 A local transport may set the &%shadow_transport%& option to the name of
21178 another local transport. Shadow remote transports are not supported.
21180 Whenever a delivery to the main transport succeeds, and either
21181 &%shadow_condition%& is unset, or its expansion does not result in the empty
21182 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
21183 passed to the shadow transport, with the same delivery address or addresses. If
21184 expansion fails, no action is taken except that non-forced expansion failures
21185 cause a log line to be written.
21187 The result of the shadow transport is discarded and does not affect the
21188 subsequent processing of the message. Only a single level of shadowing is
21189 provided; the &%shadow_transport%& option is ignored on any transport when it
21190 is running as a shadow. Options concerned with output from pipes are also
21191 ignored. The log line for the successful delivery has an item added on the end,
21194 ST=<shadow transport name>
21196 If the shadow transport did not succeed, the error message is put in
21197 parentheses afterwards. Shadow transports can be used for a number of different
21198 purposes, including keeping more detailed log information than Exim normally
21199 provides, and implementing automatic acknowledgment policies based on message
21200 headers that some sites insist on.
21203 .option transport_filter transports string&!! unset
21204 .cindex "transport" "filter"
21205 .cindex "filter" "transport filter"
21206 This option sets up a filtering (in the Unix shell sense) process for messages
21207 at transport time. It should not be confused with mail filtering as set up by
21208 individual users or via a system filter.
21209 If unset, or expanding to an empty string, no filtering is done.
21211 When the message is about to be written out, the command specified by
21212 &%transport_filter%& is started up in a separate, parallel process, and
21213 the entire message, including the header lines, is passed to it on its standard
21214 input (this in fact is done from a third process, to avoid deadlock). The
21215 command must be specified as an absolute path.
21217 The lines of the message that are written to the transport filter are
21218 terminated by newline (&"\n"&). The message is passed to the filter before any
21219 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
21220 lines beginning with a dot, and also before any processing implied by the
21221 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21222 &(pipe)& transports.
21224 The standard error for the filter process is set to the same destination as its
21225 standard output; this is read and written to the message's ultimate
21226 destination. The process that writes the message to the filter, the
21227 filter itself, and the original process that reads the result and delivers it
21228 are all run in parallel, like a shell pipeline.
21230 The filter can perform any transformations it likes, but of course should take
21231 care not to break RFC 2822 syntax. Exim does not check the result, except to
21232 test for a final newline when SMTP is in use. All messages transmitted over
21233 SMTP must end with a newline, so Exim supplies one if it is missing.
21235 .cindex "content scanning" "per user"
21236 A transport filter can be used to provide content-scanning on a per-user basis
21237 at delivery time if the only required effect of the scan is to modify the
21238 message. For example, a content scan could insert a new header line containing
21239 a spam score. This could be interpreted by a filter in the user's MUA. It is
21240 not possible to discard a message at this stage.
21242 .cindex "SMTP" "SIZE"
21243 A problem might arise if the filter increases the size of a message that is
21244 being sent down an SMTP connection. If the receiving SMTP server has indicated
21245 support for the SIZE parameter, Exim will have sent the size of the message
21246 at the start of the SMTP session. If what is actually sent is substantially
21247 more, the server might reject the message. This can be worked round by setting
21248 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21249 additions to the message, or to disable the use of SIZE altogether.
21251 .vindex "&$pipe_addresses$&"
21252 The value of the &%transport_filter%& option is the command string for starting
21253 the filter, which is run directly from Exim, not under a shell. The string is
21254 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21255 Exim breaks it up into arguments and then expands each argument separately (see
21256 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21257 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21258 of arguments, one for each address that applies to this delivery. (This isn't
21259 an ideal name for this feature here, but as it was already implemented for the
21260 &(pipe)& transport, it seemed sensible not to change it.)
21263 .vindex "&$host_address$&"
21264 The expansion variables &$host$& and &$host_address$& are available when the
21265 transport is a remote one. They contain the name and IP address of the host to
21266 which the message is being sent. For example:
21268 transport_filter = /some/directory/transport-filter.pl \
21269 $host $host_address $sender_address $pipe_addresses
21272 Two problems arise if you want to use more complicated expansion items to
21273 generate transport filter commands, both of which due to the fact that the
21274 command is split up &'before'& expansion.
21276 If an expansion item contains white space, you must quote it, so that it is all
21277 part of the same command item. If the entire option setting is one such
21278 expansion item, you have to take care what kind of quoting you use. For
21281 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21283 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21284 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21285 stripped by Exim when it read the option's value. When the value is used, if
21286 the single quotes were missing, the line would be split into two items,
21287 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21288 Exim tried to expand the first one.
21290 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21291 expansion cannot generate multiple arguments, or a command name followed by
21292 arguments. Consider this example:
21294 transport_filter = ${lookup{$host}lsearch{/a/file}\
21295 {$value}{/bin/cat}}
21297 The result of the lookup is interpreted as the name of the command, even
21298 if it contains white space. The simplest way round this is to use a shell:
21300 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21301 {$value}{/bin/cat}}
21305 The filter process is run under the same uid and gid as the normal delivery.
21306 For remote deliveries this is the Exim uid/gid by default. The command should
21307 normally yield a zero return code. Transport filters are not supposed to fail.
21308 A non-zero code is taken to mean that the transport filter encountered some
21309 serious problem. Delivery of the message is deferred; the message remains on
21310 the queue and is tried again later. It is not possible to cause a message to be
21311 bounced from a transport filter.
21313 If a transport filter is set on an autoreply transport, the original message is
21314 passed through the filter as it is being copied into the newly generated
21315 message, which happens if the &%return_message%& option is set.
21318 .option transport_filter_timeout transports time 5m
21319 .cindex "transport" "filter, timeout"
21320 When Exim is reading the output of a transport filter, it applies a timeout
21321 that can be set by this option. Exceeding the timeout is normally treated as a
21322 temporary delivery failure. However, if a transport filter is used with a
21323 &(pipe)& transport, a timeout in the transport filter is treated in the same
21324 way as a timeout in the pipe command itself. By default, a timeout is a hard
21325 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21326 becomes a temporary error.
21329 .option user transports string&!! "Exim user"
21330 .cindex "uid (user id)" "local delivery"
21331 .cindex "transport" "user, specifying"
21332 This option specifies the user under whose uid the delivery process is to be
21333 run, overriding any uid that may have been set by the router. If the user is
21334 given as a name, the uid is looked up from the password data, and the
21335 associated group is taken as the value of the gid to be used if the &%group%&
21338 For deliveries that use local transports, a user and group are normally
21339 specified explicitly or implicitly (for example, as a result of
21340 &%check_local_user%&) by the router or transport.
21342 .cindex "hints database" "access by remote transport"
21343 For remote transports, you should leave this option unset unless you really are
21344 sure you know what you are doing. When a remote transport is running, it needs
21345 to be able to access Exim's hints databases, because each host may have its own
21347 .ecindex IIDgenoptra1
21348 .ecindex IIDgenoptra2
21349 .ecindex IIDgenoptra3
21356 . ////////////////////////////////////////////////////////////////////////////
21357 . ////////////////////////////////////////////////////////////////////////////
21359 .chapter "Address batching in local transports" "CHAPbatching" &&&
21361 .cindex "transport" "local; address batching in"
21362 The only remote transport (&(smtp)&) is normally configured to handle more than
21363 one address at a time, so that when several addresses are routed to the same
21364 remote host, just one copy of the message is sent. Local transports, however,
21365 normally handle one address at a time. That is, a separate instance of the
21366 transport is run for each address that is routed to the transport. A separate
21367 copy of the message is delivered each time.
21369 .cindex "batched local delivery"
21370 .oindex "&%batch_max%&"
21371 .oindex "&%batch_id%&"
21372 In special cases, it may be desirable to handle several addresses at once in a
21373 local transport, for example:
21376 In an &(appendfile)& transport, when storing messages in files for later
21377 delivery by some other means, a single copy of the message with multiple
21378 recipients saves space.
21380 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21381 a single copy saves time, and is the normal way LMTP is expected to work.
21383 In a &(pipe)& transport, when passing the message
21384 to a scanner program or
21385 to some other delivery mechanism such as UUCP, multiple recipients may be
21389 These three local transports all have the same options for controlling multiple
21390 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21391 repeating the information for each transport, these options are described here.
21393 The &%batch_max%& option specifies the maximum number of addresses that can be
21394 delivered together in a single run of the transport. Its default value is one
21395 (no batching). When more than one address is routed to a transport that has a
21396 &%batch_max%& value greater than one, the addresses are delivered in a batch
21397 (that is, in a single run of the transport with multiple recipients), subject
21398 to certain conditions:
21401 .vindex "&$local_part$&"
21402 If any of the transport's options contain a reference to &$local_part$&, no
21403 batching is possible.
21405 .vindex "&$domain$&"
21406 If any of the transport's options contain a reference to &$domain$&, only
21407 addresses with the same domain are batched.
21409 .cindex "customizing" "batching condition"
21410 If &%batch_id%& is set, it is expanded for each address, and only those
21411 addresses with the same expanded value are batched. This allows you to specify
21412 customized batching conditions. Failure of the expansion for any reason,
21413 including forced failure, disables batching, but it does not stop the delivery
21416 Batched addresses must also have the same errors address (where to send
21417 delivery errors), the same header additions and removals, the same user and
21418 group for the transport, and if a host list is present, the first host must
21422 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21423 both when the file or pipe command is specified in the transport, and when it
21424 is specified by a &(redirect)& router, but all the batched addresses must of
21425 course be routed to the same file or pipe command. These two transports have an
21426 option called &%use_bsmtp%&, which causes them to deliver the message in
21427 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21428 &%check_string%& and &%escape_string%& options are forced to the values
21431 escape_string = ".."
21433 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21434 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21435 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21437 .cindex "&'Envelope-to:'& header line"
21438 If the generic &%envelope_to_add%& option is set for a batching transport, the
21439 &'Envelope-to:'& header that is added to the message contains all the addresses
21440 that are being processed together. If you are using a batching &(appendfile)&
21441 transport without &%use_bsmtp%&, the only way to preserve the recipient
21442 addresses is to set the &%envelope_to_add%& option.
21444 .cindex "&(pipe)& transport" "with multiple addresses"
21445 .vindex "&$pipe_addresses$&"
21446 If you are using a &(pipe)& transport without BSMTP, and setting the
21447 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21448 the command. This is not a true variable; it is a bit of magic that causes each
21449 of the recipient addresses to be inserted into the command as a separate
21450 argument. This provides a way of accessing all the addresses that are being
21451 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21452 are specified by a &(redirect)& router.
21457 . ////////////////////////////////////////////////////////////////////////////
21458 . ////////////////////////////////////////////////////////////////////////////
21460 .chapter "The appendfile transport" "CHAPappendfile"
21461 .scindex IIDapptra1 "&(appendfile)& transport"
21462 .scindex IIDapptra2 "transports" "&(appendfile)&"
21463 .cindex "directory creation"
21464 .cindex "creating directories"
21465 The &(appendfile)& transport delivers a message by appending it to an existing
21466 file, or by creating an entirely new file in a specified directory. Single
21467 files to which messages are appended can be in the traditional Unix mailbox
21468 format, or optionally in the MBX format supported by the Pine MUA and
21469 University of Washington IMAP daemon, &'inter alia'&. When each message is
21470 being delivered as a separate file, &"maildir"& format can optionally be used
21471 to give added protection against failures that happen part-way through the
21472 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21473 supported. For all file formats, Exim attempts to create as many levels of
21474 directory as necessary, provided that &%create_directory%& is set.
21476 The code for the optional formats is not included in the Exim binary by
21477 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21478 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21481 .cindex "quota" "system"
21482 Exim recognizes system quota errors, and generates an appropriate message. Exim
21483 also supports its own quota control within the transport, for use when the
21484 system facility is unavailable or cannot be used for some reason.
21486 If there is an error while appending to a file (for example, quota exceeded or
21487 partition filled), Exim attempts to reset the file's length and last
21488 modification time back to what they were before. If there is an error while
21489 creating an entirely new file, the new file is removed.
21491 Before appending to a file, a number of security checks are made, and the
21492 file is locked. A detailed description is given below, after the list of
21495 The &(appendfile)& transport is most commonly used for local deliveries to
21496 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21497 putting messages into files for remote delivery by some means other than Exim.
21498 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21503 .section "The file and directory options" "SECTfildiropt"
21504 The &%file%& option specifies a single file, to which the message is appended;
21505 the &%directory%& option specifies a directory, in which a new file containing
21506 the message is created. Only one of these two options can be set, and for
21507 normal deliveries to mailboxes, one of them &'must'& be set.
21509 .vindex "&$address_file$&"
21510 .vindex "&$local_part$&"
21511 However, &(appendfile)& is also used for delivering messages to files or
21512 directories whose names (or parts of names) are obtained from alias,
21513 forwarding, or filtering operations (for example, a &%save%& command in a
21514 user's Exim filter). When such a transport is running, &$local_part$& contains
21515 the local part that was aliased or forwarded, and &$address_file$& contains the
21516 name (or partial name) of the file or directory generated by the redirection
21517 operation. There are two cases:
21520 If neither &%file%& nor &%directory%& is set, the redirection operation
21521 must specify an absolute path (one that begins with &`/`&). This is the most
21522 common case when users with local accounts use filtering to sort mail into
21523 different folders. See for example, the &(address_file)& transport in the
21524 default configuration. If the path ends with a slash, it is assumed to be the
21525 name of a directory. A delivery to a directory can also be forced by setting
21526 &%maildir_format%& or &%mailstore_format%&.
21528 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21529 used to determine the file or directory name for the delivery. Normally, the
21530 contents of &$address_file$& are used in some way in the string expansion.
21534 .cindex "Sieve filter" "configuring &(appendfile)&"
21535 .cindex "Sieve filter" "relative mailbox path handling"
21536 As an example of the second case, consider an environment where users do not
21537 have home directories. They may be permitted to use Exim filter commands of the
21542 or Sieve filter commands of the form:
21544 require "fileinto";
21545 fileinto "folder23";
21547 In this situation, the expansion of &%file%& or &%directory%& in the transport
21548 must transform the relative path into an appropriate absolute file name. In the
21549 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21550 is used as a result of a &"keep"& action in the filter. This example shows one
21551 way of handling this requirement:
21553 file = ${if eq{$address_file}{inbox} \
21554 {/var/mail/$local_part} \
21555 {${if eq{${substr_0_1:$address_file}}{/} \
21557 {$home/mail/$address_file} \
21561 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21562 location, absolute paths are used without change, and other folders are in the
21563 &_mail_& directory within the home directory.
21565 &*Note 1*&: While processing an Exim filter, a relative path such as
21566 &_folder23_& is turned into an absolute path if a home directory is known to
21567 the router. In particular, this is the case if &%check_local_user%& is set. If
21568 you want to prevent this happening at routing time, you can set
21569 &%router_home_directory%& empty. This forces the router to pass the relative
21570 path to the transport.
21572 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21573 the &%file%& or &%directory%& option is still used if it is set.
21578 .section "Private options for appendfile" "SECID134"
21579 .cindex "options" "&(appendfile)& transport"
21583 .option allow_fifo appendfile boolean false
21584 .cindex "fifo (named pipe)"
21585 .cindex "named pipe (fifo)"
21586 .cindex "pipe" "named (fifo)"
21587 Setting this option permits delivery to named pipes (FIFOs) as well as to
21588 regular files. If no process is reading the named pipe at delivery time, the
21589 delivery is deferred.
21592 .option allow_symlink appendfile boolean false
21593 .cindex "symbolic link" "to mailbox"
21594 .cindex "mailbox" "symbolic link"
21595 By default, &(appendfile)& will not deliver if the path name for the file is
21596 that of a symbolic link. Setting this option relaxes that constraint, but there
21597 are security issues involved in the use of symbolic links. Be sure you know
21598 what you are doing if you set this. Details of exactly what this option affects
21599 are included in the discussion which follows this list of options.
21602 .option batch_id appendfile string&!! unset
21603 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21604 However, batching is automatically disabled for &(appendfile)& deliveries that
21605 happen as a result of forwarding or aliasing or other redirection directly to a
21609 .option batch_max appendfile integer 1
21610 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21613 .option check_group appendfile boolean false
21614 When this option is set, the group owner of the file defined by the &%file%&
21615 option is checked to see that it is the same as the group under which the
21616 delivery process is running. The default setting is false because the default
21617 file mode is 0600, which means that the group is irrelevant.
21620 .option check_owner appendfile boolean true
21621 When this option is set, the owner of the file defined by the &%file%& option
21622 is checked to ensure that it is the same as the user under which the delivery
21623 process is running.
21626 .option check_string appendfile string "see below"
21627 .cindex "&""From""& line"
21628 As &(appendfile)& writes the message, the start of each line is tested for
21629 matching &%check_string%&, and if it does, the initial matching characters are
21630 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21631 a literal string, not a regular expression, and the case of any letters it
21632 contains is significant.
21634 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21635 are forced to &"."& and &".."& respectively, and any settings in the
21636 configuration are ignored. Otherwise, they default to &"From&~"& and
21637 &">From&~"& when the &%file%& option is set, and unset when any of the
21638 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21640 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21641 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21642 &"From&~"& indicates the start of a new message. All four options need changing
21643 if another format is used. For example, to deliver to mailboxes in MMDF format:
21644 .cindex "MMDF format mailbox"
21645 .cindex "mailbox" "MMDF format"
21647 check_string = "\1\1\1\1\n"
21648 escape_string = "\1\1\1\1 \n"
21649 message_prefix = "\1\1\1\1\n"
21650 message_suffix = "\1\1\1\1\n"
21652 .option create_directory appendfile boolean true
21653 .cindex "directory creation"
21654 When this option is true, Exim attempts to create any missing superior
21655 directories for the file that it is about to write. A created directory's mode
21656 is given by the &%directory_mode%& option.
21658 The group ownership of a newly created directory is highly dependent on the
21659 operating system (and possibly the file system) that is being used. For
21660 example, in Solaris, if the parent directory has the setgid bit set, its group
21661 is propagated to the child; if not, the currently set group is used. However,
21662 in FreeBSD, the parent's group is always used.
21666 .option create_file appendfile string anywhere
21667 This option constrains the location of files and directories that are created
21668 by this transport. It applies to files defined by the &%file%& option and
21669 directories defined by the &%directory%& option. In the case of maildir
21670 delivery, it applies to the top level directory, not the maildir directories
21673 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21674 &"belowhome"&. In the second and third cases, a home directory must have been
21675 set for the transport. This option is not useful when an explicit file name is
21676 given for normal mailbox deliveries. It is intended for the case when file
21677 names are generated from users' &_.forward_& files. These are usually handled
21678 by an &(appendfile)& transport called &%address_file%&. See also
21679 &%file_must_exist%&.
21682 .option directory appendfile string&!! unset
21683 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21684 or &%directory%& must be set, unless the delivery is the direct result of a
21685 redirection (see section &<<SECTfildiropt>>&).
21687 When &%directory%& is set, the string is expanded, and the message is delivered
21688 into a new file or files in or below the given directory, instead of being
21689 appended to a single mailbox file. A number of different formats are provided
21690 (see &%maildir_format%& and &%mailstore_format%&), and see section
21691 &<<SECTopdir>>& for further details of this form of delivery.
21694 .option directory_file appendfile string&!! "see below"
21696 .vindex "&$inode$&"
21697 When &%directory%& is set, but neither &%maildir_format%& nor
21698 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21699 whose name is obtained by expanding this string. The default value is:
21701 q${base62:$tod_epoch}-$inode
21703 This generates a unique name from the current time, in base 62 form, and the
21704 inode of the file. The variable &$inode$& is available only when expanding this
21708 .option directory_mode appendfile "octal integer" 0700
21709 If &(appendfile)& creates any directories as a result of the
21710 &%create_directory%& option, their mode is specified by this option.
21713 .option escape_string appendfile string "see description"
21714 See &%check_string%& above.
21717 .option file appendfile string&!! unset
21718 This option is mutually exclusive with the &%directory%& option, but one of
21719 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21720 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
21721 specifies a single file, to which the message is appended. One or more of
21722 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
21725 .cindex "NFS" "lock file"
21726 .cindex "locking files"
21727 .cindex "lock files"
21728 If you are using more than one host to deliver over NFS into the same
21729 mailboxes, you should always use lock files.
21731 The string value is expanded for each delivery, and must yield an absolute
21732 path. The most common settings of this option are variations on one of these
21735 file = /var/spool/mail/$local_part
21736 file = /home/$local_part/inbox
21739 .cindex "&""sticky""& bit"
21740 In the first example, all deliveries are done into the same directory. If Exim
21741 is configured to use lock files (see &%use_lockfile%& below) it must be able to
21742 create a file in the directory, so the &"sticky"& bit must be turned on for
21743 deliveries to be possible, or alternatively the &%group%& option can be used to
21744 run the delivery under a group id which has write access to the directory.
21748 .option file_format appendfile string unset
21749 .cindex "file" "mailbox; checking existing format"
21750 This option requests the transport to check the format of an existing file
21751 before adding to it. The check consists of matching a specific string at the
21752 start of the file. The value of the option consists of an even number of
21753 colon-separated strings. The first of each pair is the test string, and the
21754 second is the name of a transport. If the transport associated with a matched
21755 string is not the current transport, control is passed over to the other
21756 transport. For example, suppose the standard &(local_delivery)& transport has
21759 file_format = "From : local_delivery :\
21760 \1\1\1\1\n : local_mmdf_delivery"
21762 Mailboxes that begin with &"From"& are still handled by this transport, but if
21763 a mailbox begins with four binary ones followed by a newline, control is passed
21764 to a transport called &%local_mmdf_delivery%&, which presumably is configured
21765 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
21766 is assumed to match the current transport. If the start of a mailbox doesn't
21767 match any string, or if the transport named for a given string is not defined,
21768 delivery is deferred.
21771 .option file_must_exist appendfile boolean false
21772 If this option is true, the file specified by the &%file%& option must exist.
21773 A temporary error occurs if it does not, causing delivery to be deferred.
21774 If this option is false, the file is created if it does not exist.
21777 .option lock_fcntl_timeout appendfile time 0s
21778 .cindex "timeout" "mailbox locking"
21779 .cindex "mailbox" "locking, blocking and non-blocking"
21780 .cindex "locking files"
21781 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
21782 when locking an open mailbox file. If the call fails, the delivery process
21783 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
21784 Non-blocking calls are used so that the file is not kept open during the wait
21785 for the lock; the reason for this is to make it as safe as possible for
21786 deliveries over NFS in the case when processes might be accessing an NFS
21787 mailbox without using a lock file. This should not be done, but
21788 misunderstandings and hence misconfigurations are not unknown.
21790 On a busy system, however, the performance of a non-blocking lock approach is
21791 not as good as using a blocking lock with a timeout. In this case, the waiting
21792 is done inside the system call, and Exim's delivery process acquires the lock
21793 and can proceed as soon as the previous lock holder releases it.
21795 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
21796 timeout, are used. There may still be some retrying: the maximum number of
21799 (lock_retries * lock_interval) / lock_fcntl_timeout
21801 rounded up to the next whole number. In other words, the total time during
21802 which &(appendfile)& is trying to get a lock is roughly the same, unless
21803 &%lock_fcntl_timeout%& is set very large.
21805 You should consider setting this option if you are getting a lot of delayed
21806 local deliveries because of errors of the form
21808 failed to lock mailbox /some/file (fcntl)
21811 .option lock_flock_timeout appendfile time 0s
21812 This timeout applies to file locking when using &[flock()]& (see
21813 &%use_flock%&); the timeout operates in a similar manner to
21814 &%lock_fcntl_timeout%&.
21817 .option lock_interval appendfile time 3s
21818 This specifies the time to wait between attempts to lock the file. See below
21819 for details of locking.
21822 .option lock_retries appendfile integer 10
21823 This specifies the maximum number of attempts to lock the file. A value of zero
21824 is treated as 1. See below for details of locking.
21827 .option lockfile_mode appendfile "octal integer" 0600
21828 This specifies the mode of the created lock file, when a lock file is being
21829 used (see &%use_lockfile%& and &%use_mbx_lock%&).
21832 .option lockfile_timeout appendfile time 30m
21833 .cindex "timeout" "mailbox locking"
21834 When a lock file is being used (see &%use_lockfile%&), if a lock file already
21835 exists and is older than this value, it is assumed to have been left behind by
21836 accident, and Exim attempts to remove it.
21839 .option mailbox_filecount appendfile string&!! unset
21840 .cindex "mailbox" "specifying size of"
21841 .cindex "size" "of mailbox"
21842 If this option is set, it is expanded, and the result is taken as the current
21843 number of files in the mailbox. It must be a decimal number, optionally
21844 followed by K or M. This provides a way of obtaining this information from an
21845 external source that maintains the data.
21848 .option mailbox_size appendfile string&!! unset
21849 .cindex "mailbox" "specifying size of"
21850 .cindex "size" "of mailbox"
21851 If this option is set, it is expanded, and the result is taken as the current
21852 size the mailbox. It must be a decimal number, optionally followed by K or M.
21853 This provides a way of obtaining this information from an external source that
21854 maintains the data. This is likely to be helpful for maildir deliveries where
21855 it is computationally expensive to compute the size of a mailbox.
21859 .option maildir_format appendfile boolean false
21860 .cindex "maildir format" "specifying"
21861 If this option is set with the &%directory%& option, the delivery is into a new
21862 file, in the &"maildir"& format that is used by other mail software. When the
21863 transport is activated directly from a &(redirect)& router (for example, the
21864 &(address_file)& transport in the default configuration), setting
21865 &%maildir_format%& causes the path received from the router to be treated as a
21866 directory, whether or not it ends with &`/`&. This option is available only if
21867 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
21868 &<<SECTmaildirdelivery>>& below for further details.
21871 .option maildir_quota_directory_regex appendfile string "See below"
21872 .cindex "maildir format" "quota; directories included in"
21873 .cindex "quota" "maildir; directories included in"
21874 This option is relevant only when &%maildir_use_size_file%& is set. It defines
21875 a regular expression for specifying directories, relative to the quota
21876 directory (see &%quota_directory%&), that should be included in the quota
21877 calculation. The default value is:
21879 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
21881 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
21882 (directories whose names begin with a dot). If you want to exclude the
21884 folder from the count (as some sites do), you need to change this setting to
21886 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
21888 This uses a negative lookahead in the regular expression to exclude the
21889 directory whose name is &_.Trash_&. When a directory is excluded from quota
21890 calculations, quota processing is bypassed for any messages that are delivered
21891 directly into that directory.
21894 .option maildir_retries appendfile integer 10
21895 This option specifies the number of times to retry when writing a file in
21896 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
21899 .option maildir_tag appendfile string&!! unset
21900 This option applies only to deliveries in maildir format, and is described in
21901 section &<<SECTmaildirdelivery>>& below.
21904 .option maildir_use_size_file appendfile&!! boolean false
21905 .cindex "maildir format" "&_maildirsize_& file"
21906 The result of string expansion for this option must be a valid boolean value.
21907 If it is true, it enables support for &_maildirsize_& files. Exim
21908 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
21909 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
21910 value is zero. See &%maildir_quota_directory_regex%& above and section
21911 &<<SECTmaildirdelivery>>& below for further details.
21913 .option maildirfolder_create_regex appendfile string unset
21914 .cindex "maildir format" "&_maildirfolder_& file"
21915 .cindex "&_maildirfolder_&, creating"
21916 The value of this option is a regular expression. If it is unset, it has no
21917 effect. Otherwise, before a maildir delivery takes place, the pattern is
21918 matched against the name of the maildir directory, that is, the directory
21919 containing the &_new_& and &_tmp_& subdirectories that will be used for the
21920 delivery. If there is a match, Exim checks for the existence of a file called
21921 &_maildirfolder_& in the directory, and creates it if it does not exist.
21922 See section &<<SECTmaildirdelivery>>& for more details.
21925 .option mailstore_format appendfile boolean false
21926 .cindex "mailstore format" "specifying"
21927 If this option is set with the &%directory%& option, the delivery is into two
21928 new files in &"mailstore"& format. The option is available only if
21929 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
21930 below for further details.
21933 .option mailstore_prefix appendfile string&!! unset
21934 This option applies only to deliveries in mailstore format, and is described in
21935 section &<<SECTopdir>>& below.
21938 .option mailstore_suffix appendfile string&!! unset
21939 This option applies only to deliveries in mailstore format, and is described in
21940 section &<<SECTopdir>>& below.
21943 .option mbx_format appendfile boolean false
21944 .cindex "locking files"
21945 .cindex "file" "locking"
21946 .cindex "file" "MBX format"
21947 .cindex "MBX format, specifying"
21948 This option is available only if Exim has been compiled with SUPPORT_MBX
21949 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
21950 the message is appended to the mailbox file in MBX format instead of
21951 traditional Unix format. This format is supported by Pine4 and its associated
21952 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
21954 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
21955 automatically changed by the use of &%mbx_format%&. They should normally be set
21956 empty when using MBX format, so this option almost always appears in this
21963 If none of the locking options are mentioned in the configuration,
21964 &%use_mbx_lock%& is assumed and the other locking options default to false. It
21965 is possible to specify the other kinds of locking with &%mbx_format%&, but
21966 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
21967 interworks with &'c-client'&, providing for shared access to the mailbox. It
21968 should not be used if any program that does not use this form of locking is
21969 going to access the mailbox, nor should it be used if the mailbox file is NFS
21970 mounted, because it works only when the mailbox is accessed from a single host.
21972 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
21973 the standard version of &'c-client'&, because as long as it has a mailbox open
21974 (this means for the whole of a Pine or IMAP session), Exim will not be able to
21975 append messages to it.
21978 .option message_prefix appendfile string&!! "see below"
21979 .cindex "&""From""& line"
21980 The string specified here is expanded and output at the start of every message.
21981 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21982 in which case it is:
21984 message_prefix = "From ${if def:return_path{$return_path}\
21985 {MAILER-DAEMON}} $tod_bsdinbox\n"
21987 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21988 &`\n`& to &`\r\n`& in &%message_prefix%&.
21990 .option message_suffix appendfile string&!! "see below"
21991 The string specified here is expanded and output at the end of every message.
21992 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
21993 in which case it is a single newline character. The suffix can be suppressed by
21998 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
21999 &`\n`& to &`\r\n`& in &%message_suffix%&.
22001 .option mode appendfile "octal integer" 0600
22002 If the output file is created, it is given this mode. If it already exists and
22003 has wider permissions, they are reduced to this mode. If it has narrower
22004 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
22005 if the delivery is the result of a &%save%& command in a filter file specifying
22006 a particular mode, the mode of the output file is always forced to take that
22007 value, and this option is ignored.
22010 .option mode_fail_narrower appendfile boolean true
22011 This option applies in the case when an existing mailbox file has a narrower
22012 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
22013 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
22014 continues with the delivery attempt, using the existing mode of the file.
22017 .option notify_comsat appendfile boolean false
22018 If this option is true, the &'comsat'& daemon is notified after every
22019 successful delivery to a user mailbox. This is the daemon that notifies logged
22020 on users about incoming mail.
22023 .option quota appendfile string&!! unset
22024 .cindex "quota" "imposed by Exim"
22025 This option imposes a limit on the size of the file to which Exim is appending,
22026 or to the total space used in the directory tree when the &%directory%& option
22027 is set. In the latter case, computation of the space used is expensive, because
22028 all the files in the directory (and any sub-directories) have to be
22029 individually inspected and their sizes summed. (See &%quota_size_regex%& and
22030 &%maildir_use_size_file%& for ways to avoid this in environments where users
22031 have no shell access to their mailboxes).
22033 As there is no interlock against two simultaneous deliveries into a
22034 multi-file mailbox, it is possible for the quota to be overrun in this case.
22035 For single-file mailboxes, of course, an interlock is a necessity.
22037 A file's size is taken as its &'used'& value. Because of blocking effects, this
22038 may be a lot less than the actual amount of disk space allocated to the file.
22039 If the sizes of a number of files are being added up, the rounding effect can
22040 become quite noticeable, especially on systems that have large block sizes.
22041 Nevertheless, it seems best to stick to the &'used'& figure, because this is
22042 the obvious value which users understand most easily.
22044 The value of the option is expanded, and must then be a numerical value
22045 (decimal point allowed), optionally followed by one of the letters K, M, or G,
22046 for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
22047 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
22050 &*Note*&: A value of zero is interpreted as &"no quota"&.
22052 The expansion happens while Exim is running as root, before it changes uid for
22053 the delivery. This means that files that are inaccessible to the end user can
22054 be used to hold quota values that are looked up in the expansion. When delivery
22055 fails because this quota is exceeded, the handling of the error is as for
22056 system quota failures.
22058 By default, Exim's quota checking mimics system quotas, and restricts the
22059 mailbox to the specified maximum size, though the value is not accurate to the
22060 last byte, owing to separator lines and additional headers that may get added
22061 during message delivery. When a mailbox is nearly full, large messages may get
22062 refused even though small ones are accepted, because the size of the current
22063 message is added to the quota when the check is made. This behaviour can be
22064 changed by setting &%quota_is_inclusive%& false. When this is done, the check
22065 for exceeding the quota does not include the current message. Thus, deliveries
22066 continue until the quota has been exceeded; thereafter, no further messages are
22067 delivered. See also &%quota_warn_threshold%&.
22070 .option quota_directory appendfile string&!! unset
22071 This option defines the directory to check for quota purposes when delivering
22072 into individual files. The default is the delivery directory, or, if a file
22073 called &_maildirfolder_& exists in a maildir directory, the parent of the
22074 delivery directory.
22077 .option quota_filecount appendfile string&!! 0
22078 This option applies when the &%directory%& option is set. It limits the total
22079 number of files in the directory (compare the inode limit in system quotas). It
22080 can only be used if &%quota%& is also set. The value is expanded; an expansion
22081 failure causes delivery to be deferred. A value of zero is interpreted as
22085 .option quota_is_inclusive appendfile boolean true
22086 See &%quota%& above.
22089 .option quota_size_regex appendfile string unset
22090 This option applies when one of the delivery modes that writes a separate file
22091 for each message is being used. When Exim wants to find the size of one of
22092 these files in order to test the quota, it first checks &%quota_size_regex%&.
22093 If this is set to a regular expression that matches the file name, and it
22094 captures one string, that string is interpreted as a representation of the
22095 file's size. The value of &%quota_size_regex%& is not expanded.
22097 This feature is useful only when users have no shell access to their mailboxes
22098 &-- otherwise they could defeat the quota simply by renaming the files. This
22099 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
22100 the file length to the file name. For example:
22102 maildir_tag = ,S=$message_size
22103 quota_size_regex = ,S=(\d+)
22105 An alternative to &$message_size$& is &$message_linecount$&, which contains the
22106 number of lines in the message.
22108 The regular expression should not assume that the length is at the end of the
22109 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
22110 sometimes add other information onto the ends of message file names.
22112 Section &<<SECID136>>& contains further information.
22115 .option quota_warn_message appendfile string&!! "see below"
22116 See below for the use of this option. If it is not set when
22117 &%quota_warn_threshold%& is set, it defaults to
22119 quota_warn_message = "\
22120 To: $local_part@$domain\n\
22121 Subject: Your mailbox\n\n\
22122 This message is automatically created \
22123 by mail delivery software.\n\n\
22124 The size of your mailbox has exceeded \
22125 a warning threshold that is\n\
22126 set by the system administrator.\n"
22130 .option quota_warn_threshold appendfile string&!! 0
22131 .cindex "quota" "warning threshold"
22132 .cindex "mailbox" "size warning"
22133 .cindex "size" "of mailbox"
22134 This option is expanded in the same way as &%quota%& (see above). If the
22135 resulting value is greater than zero, and delivery of the message causes the
22136 size of the file or total space in the directory tree to cross the given
22137 threshold, a warning message is sent. If &%quota%& is also set, the threshold
22138 may be specified as a percentage of it by following the value with a percent
22142 quota_warn_threshold = 75%
22144 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
22145 percent sign is ignored.
22147 The warning message itself is specified by the &%quota_warn_message%& option,
22148 and it must start with a &'To:'& header line containing the recipient(s) of the
22149 warning message. These do not necessarily have to include the recipient(s) of
22150 the original message. A &'Subject:'& line should also normally be supplied. You
22151 can include any other header lines that you want. If you do not include a
22152 &'From:'& line, the default is:
22154 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
22156 .oindex &%errors_reply_to%&
22157 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
22160 The &%quota%& option does not have to be set in order to use this option; they
22161 are independent of one another except when the threshold is specified as a
22165 .option use_bsmtp appendfile boolean false
22166 .cindex "envelope sender"
22167 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
22168 format, with the envelope sender and recipient(s) included as SMTP commands. If
22169 you want to include a leading HELO command with such messages, you can do
22170 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
22171 for details of batch SMTP.
22174 .option use_crlf appendfile boolean false
22175 .cindex "carriage return"
22177 This option causes lines to be terminated with the two-character CRLF sequence
22178 (carriage return, linefeed) instead of just a linefeed character. In the case
22179 of batched SMTP, the byte sequence written to the file is then an exact image
22180 of what would be sent down a real SMTP connection.
22182 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
22183 (which are used to supply the traditional &"From&~"& and blank line separators
22184 in Berkeley-style mailboxes) are written verbatim, so must contain their own
22185 carriage return characters if these are needed. In cases where these options
22186 have non-empty defaults, the values end with a single linefeed, so they must be
22187 changed to end with &`\r\n`& if &%use_crlf%& is set.
22190 .option use_fcntl_lock appendfile boolean "see below"
22191 This option controls the use of the &[fcntl()]& function to lock a file for
22192 exclusive use when a message is being appended. It is set by default unless
22193 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
22194 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
22195 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
22198 .option use_flock_lock appendfile boolean false
22199 This option is provided to support the use of &[flock()]& for file locking, for
22200 the few situations where it is needed. Most modern operating systems support
22201 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
22202 each other. Exim uses &[fcntl()]& locking by default.
22204 This option is required only if you are using an operating system where
22205 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
22206 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
22207 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
22209 .cindex "Solaris" "&[flock()]& support"
22210 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
22211 have it (and some, I think, provide a not quite right version built on top of
22212 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
22213 the ability to use it, and any attempt to do so will cause a configuration
22216 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
22217 is just being mapped onto &[fcntl()]& by the OS).
22220 .option use_lockfile appendfile boolean "see below"
22221 If this option is turned off, Exim does not attempt to create a lock file when
22222 appending to a mailbox file. In this situation, the only locking is by
22223 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22224 sure that every MUA that is ever going to look at your users' mailboxes uses
22225 &[fcntl()]& rather than a lock file, and even then only when you are not
22226 delivering over NFS from more than one host.
22228 .cindex "NFS" "lock file"
22229 In order to append to an NFS file safely from more than one host, it is
22230 necessary to take out a lock &'before'& opening the file, and the lock file
22231 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22234 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22235 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22236 except when &%mbx_format%& is set.
22239 .option use_mbx_lock appendfile boolean "see below"
22240 This option is available only if Exim has been compiled with SUPPORT_MBX
22241 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22242 locking rules be used. It is set by default if &%mbx_format%& is set and none
22243 of the locking options are mentioned in the configuration. The locking rules
22244 are the same as are used by the &'c-client'& library that underlies Pine and
22245 the IMAP4 and POP daemons that come with it (see the discussion below). The
22246 rules allow for shared access to the mailbox. However, this kind of locking
22247 does not work when the mailbox is NFS mounted.
22249 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22250 &%use_flock_lock%& to control what kind of locking is used in implementing the
22251 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22252 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22257 .section "Operational details for appending" "SECTopappend"
22258 .cindex "appending to a file"
22259 .cindex "file" "appending"
22260 Before appending to a file, the following preparations are made:
22263 If the name of the file is &_/dev/null_&, no action is taken, and a success
22267 .cindex "directory creation"
22268 If any directories on the file's path are missing, Exim creates them if the
22269 &%create_directory%& option is set. A created directory's mode is given by the
22270 &%directory_mode%& option.
22273 If &%file_format%& is set, the format of an existing file is checked. If this
22274 indicates that a different transport should be used, control is passed to that
22278 .cindex "file" "locking"
22279 .cindex "locking files"
22280 .cindex "NFS" "lock file"
22281 If &%use_lockfile%& is set, a lock file is built in a way that will work
22282 reliably over NFS, as follows:
22285 Create a &"hitching post"& file whose name is that of the lock file with the
22286 current time, primary host name, and process id added, by opening for writing
22287 as a new file. If this fails with an access error, delivery is deferred.
22289 Close the hitching post file, and hard link it to the lock file name.
22291 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22292 Unlink the hitching post name.
22294 Otherwise, use &[stat()]& to get information about the hitching post file, and
22295 then unlink hitching post name. If the number of links is exactly two, creation
22296 of the lock file succeeded but something (for example, an NFS server crash and
22297 restart) caused this fact not to be communicated to the &[link()]& call.
22299 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22300 up to &%lock_retries%& times. However, since any program that writes to a
22301 mailbox should complete its task very quickly, it is reasonable to time out old
22302 lock files that are normally the result of user agent and system crashes. If an
22303 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22304 it before trying again.
22308 A call is made to &[lstat()]& to discover whether the main file exists, and if
22309 so, what its characteristics are. If &[lstat()]& fails for any reason other
22310 than non-existence, delivery is deferred.
22313 .cindex "symbolic link" "to mailbox"
22314 .cindex "mailbox" "symbolic link"
22315 If the file does exist and is a symbolic link, delivery is deferred, unless the
22316 &%allow_symlink%& option is set, in which case the ownership of the link is
22317 checked, and then &[stat()]& is called to find out about the real file, which
22318 is then subjected to the checks below. The check on the top-level link
22319 ownership prevents one user creating a link for another's mailbox in a sticky
22320 directory, though allowing symbolic links in this case is definitely not a good
22321 idea. If there is a chain of symbolic links, the intermediate ones are not
22325 If the file already exists but is not a regular file, or if the file's owner
22326 and group (if the group is being checked &-- see &%check_group%& above) are
22327 different from the user and group under which the delivery is running,
22328 delivery is deferred.
22331 If the file's permissions are more generous than specified, they are reduced.
22332 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22333 is set false, in which case the delivery is tried using the existing
22337 The file's inode number is saved, and the file is then opened for appending.
22338 If this fails because the file has vanished, &(appendfile)& behaves as if it
22339 hadn't existed (see below). For any other failures, delivery is deferred.
22342 If the file is opened successfully, check that the inode number hasn't
22343 changed, that it is still a regular file, and that the owner and permissions
22344 have not changed. If anything is wrong, defer delivery and freeze the message.
22347 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22348 option is set. Otherwise, check that the file is being created in a permitted
22349 directory if the &%create_file%& option is set (deferring on failure), and then
22350 open for writing as a new file, with the O_EXCL and O_CREAT options,
22351 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22352 set). In this case, which can happen if the link points to a non-existent file,
22353 the file is opened for writing using O_CREAT but not O_EXCL, because
22354 that prevents link following.
22357 .cindex "loop" "while file testing"
22358 If opening fails because the file exists, obey the tests given above for
22359 existing files. However, to avoid looping in a situation where the file is
22360 being continuously created and destroyed, the exists/not-exists loop is broken
22361 after 10 repetitions, and the message is then frozen.
22364 If opening fails with any other error, defer delivery.
22367 .cindex "file" "locking"
22368 .cindex "locking files"
22369 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22370 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22371 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22372 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22373 file, and an exclusive lock on the file whose name is
22375 /tmp/.<device-number>.<inode-number>
22377 using the device and inode numbers of the open mailbox file, in accordance with
22378 the MBX locking rules. This file is created with a mode that is specified by
22379 the &%lockfile_mode%& option.
22381 If Exim fails to lock the file, there are two possible courses of action,
22382 depending on the value of the locking timeout. This is obtained from
22383 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22385 If the timeout value is zero, the file is closed, Exim waits for
22386 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22387 to lock it again. This happens up to &%lock_retries%& times, after which the
22388 delivery is deferred.
22390 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22391 &[flock()]& are used (with the given timeout), so there has already been some
22392 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22393 immediately. It retries up to
22395 (lock_retries * lock_interval) / <timeout>
22397 times (rounded up).
22400 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22401 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22404 .section "Operational details for delivery to a new file" "SECTopdir"
22405 .cindex "delivery" "to single file"
22406 .cindex "&""From""& line"
22407 When the &%directory%& option is set instead of &%file%&, each message is
22408 delivered into a newly-created file or set of files. When &(appendfile)& is
22409 activated directly from a &(redirect)& router, neither &%file%& nor
22410 &%directory%& is normally set, because the path for delivery is supplied by the
22411 router. (See for example, the &(address_file)& transport in the default
22412 configuration.) In this case, delivery is to a new file if either the path name
22413 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22415 No locking is required while writing the message to a new file, so the various
22416 locking options of the transport are ignored. The &"From"& line that by default
22417 separates messages in a single file is not normally needed, nor is the escaping
22418 of message lines that start with &"From"&, and there is no need to ensure a
22419 newline at the end of each message. Consequently, the default values for
22420 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22421 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22423 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22424 the files in the delivery directory by default. However, you can specify a
22425 different directory by setting &%quota_directory%&. Also, for maildir
22426 deliveries (see below) the &_maildirfolder_& convention is honoured.
22429 .cindex "maildir format"
22430 .cindex "mailstore format"
22431 There are three different ways in which delivery to individual files can be
22432 done, controlled by the settings of the &%maildir_format%& and
22433 &%mailstore_format%& options. Note that code to support maildir or mailstore
22434 formats is not included in the binary unless SUPPORT_MAILDIR or
22435 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22437 .cindex "directory creation"
22438 In all three cases an attempt is made to create the directory and any necessary
22439 sub-directories if they do not exist, provided that the &%create_directory%&
22440 option is set (the default). The location of a created directory can be
22441 constrained by setting &%create_file%&. A created directory's mode is given by
22442 the &%directory_mode%& option. If creation fails, or if the
22443 &%create_directory%& option is not set when creation is required, delivery is
22448 .section "Maildir delivery" "SECTmaildirdelivery"
22449 .cindex "maildir format" "description of"
22450 If the &%maildir_format%& option is true, Exim delivers each message by writing
22451 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22452 directory that is defined by the &%directory%& option (the &"delivery
22453 directory"&). If the delivery is successful, the file is renamed into the
22454 &_new_& subdirectory.
22456 In the file name, <&'stime'&> is the current time of day in seconds, and
22457 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22458 Exim checks that the time-of-day clock has moved on by at least one microsecond
22459 before terminating the delivery process. This guarantees uniqueness for the
22460 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22461 opening it. If any response other than ENOENT (does not exist) is given,
22462 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22464 Before Exim carries out a maildir delivery, it ensures that subdirectories
22465 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22466 do not exist, Exim tries to create them and any superior directories in their
22467 path, subject to the &%create_directory%& and &%create_file%& options. If the
22468 &%maildirfolder_create_regex%& option is set, and the regular expression it
22469 contains matches the delivery directory, Exim also ensures that a file called
22470 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22471 &_maildirfolder_& file cannot be created, delivery is deferred.
22473 These features make it possible to use Exim to create all the necessary files
22474 and directories in a maildir mailbox, including subdirectories for maildir++
22475 folders. Consider this example:
22477 maildir_format = true
22478 directory = /var/mail/$local_part\
22479 ${if eq{$local_part_suffix}{}{}\
22480 {/.${substr_1:$local_part_suffix}}}
22481 maildirfolder_create_regex = /\.[^/]+$
22483 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22484 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22485 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22486 not match this name, so Exim will not look for or create the file
22487 &_/var/mail/pimbo/maildirfolder_&, though it will create
22488 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22490 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22491 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22492 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22493 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22494 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22496 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22497 not inadvertently match the toplevel maildir directory, because a
22498 &_maildirfolder_& file at top level would completely break quota calculations.
22500 .cindex "quota" "in maildir delivery"
22501 .cindex "maildir++"
22502 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22503 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22504 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22505 Exim assumes the directory is a maildir++ folder directory, which is one level
22506 down from the user's top level mailbox directory. This causes it to start at
22507 the parent directory instead of the current directory when calculating the
22508 amount of space used.
22510 One problem with delivering into a multi-file mailbox is that it is
22511 computationally expensive to compute the size of the mailbox for quota
22512 checking. Various approaches have been taken to reduce the amount of work
22513 needed. The next two sections describe two of them. A third alternative is to
22514 use some external process for maintaining the size data, and use the expansion
22515 of the &%mailbox_size%& option as a way of importing it into Exim.
22520 .section "Using tags to record message sizes" "SECID135"
22521 If &%maildir_tag%& is set, the string is expanded for each delivery.
22522 When the maildir file is renamed into the &_new_& sub-directory, the
22523 tag is added to its name. However, if adding the tag takes the length of the
22524 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22525 the tag is dropped and the maildir file is created with no tag.
22528 .vindex "&$message_size$&"
22529 Tags can be used to encode the size of files in their names; see
22530 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22531 happens after the message has been written. The value of the &$message_size$&
22532 variable is set to the number of bytes actually written. If the expansion is
22533 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22534 be deferred. The expanded tag may contain any printing characters except &"/"&.
22535 Non-printing characters in the string are ignored; if the resulting string is
22536 empty, it is ignored. If it starts with an alphanumeric character, a leading
22537 colon is inserted; this default has not proven to be the path that popular
22538 maildir implementations have chosen (but changing it in Exim would break
22539 backwards compatibility).
22541 For one common implementation, you might set:
22543 maildir_tag = ,S=${message_size}
22545 but you should check the documentation of the other software to be sure.
22547 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22548 as this allows Exim to extract the size from your tag, instead of having to
22549 &[stat()]& each message file.
22552 .section "Using a maildirsize file" "SECID136"
22553 .cindex "quota" "in maildir delivery"
22554 .cindex "maildir format" "&_maildirsize_& file"
22555 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22556 storing quota and message size information in a file called &_maildirsize_&
22557 within the toplevel maildir directory. If this file does not exist, Exim
22558 creates it, setting the quota from the &%quota%& option of the transport. If
22559 the maildir directory itself does not exist, it is created before any attempt
22560 to write a &_maildirsize_& file.
22562 The &_maildirsize_& file is used to hold information about the sizes of
22563 messages in the maildir, thus speeding up quota calculations. The quota value
22564 in the file is just a cache; if the quota is changed in the transport, the new
22565 value overrides the cached value when the next message is delivered. The cache
22566 is maintained for the benefit of other programs that access the maildir and
22567 need to know the quota.
22569 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22570 file is maintained (with a zero quota setting), but no quota is imposed.
22572 A regular expression is available for controlling which directories in the
22573 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22574 See the description of the &%maildir_quota_directory_regex%& option above for
22578 .section "Mailstore delivery" "SECID137"
22579 .cindex "mailstore format" "description of"
22580 If the &%mailstore_format%& option is true, each message is written as two
22581 files in the given directory. A unique base name is constructed from the
22582 message id and the current delivery process, and the files that are written use
22583 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22584 contains the message's envelope, and the &_.msg_& file contains the message
22585 itself. The base name is placed in the variable &$mailstore_basename$&.
22587 During delivery, the envelope is first written to a file with the suffix
22588 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22589 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22590 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22591 file before accessing either of them. An alternative approach is to wait for
22592 the absence of a &_.tmp_& file.
22594 The envelope file starts with any text defined by the &%mailstore_prefix%&
22595 option, expanded and terminated by a newline if there isn't one. Then follows
22596 the sender address on one line, then all the recipient addresses, one per line.
22597 There can be more than one recipient only if the &%batch_max%& option is set
22598 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22599 appended to the file, followed by a newline if it does not end with one.
22601 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22602 failure, it is ignored. Other expansion errors are treated as serious
22603 configuration errors, and delivery is deferred. The variable
22604 &$mailstore_basename$& is available for use during these expansions.
22607 .section "Non-special new file delivery" "SECID138"
22608 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22609 file is created directly in the named directory. For example, when delivering
22610 messages into files in batched SMTP format for later delivery to some host (see
22611 section &<<SECTbatchSMTP>>&), a setting such as
22613 directory = /var/bsmtp/$host
22615 might be used. A message is written to a file with a temporary name, which is
22616 then renamed when the delivery is complete. The final name is obtained by
22617 expanding the contents of the &%directory_file%& option.
22618 .ecindex IIDapptra1
22619 .ecindex IIDapptra2
22626 . ////////////////////////////////////////////////////////////////////////////
22627 . ////////////////////////////////////////////////////////////////////////////
22629 .chapter "The autoreply transport" "CHID8"
22630 .scindex IIDauttra1 "transports" "&(autoreply)&"
22631 .scindex IIDauttra2 "&(autoreply)& transport"
22632 The &(autoreply)& transport is not a true transport in that it does not cause
22633 the message to be transmitted. Instead, it generates a new mail message as an
22634 automatic reply to the incoming message. &'References:'& and
22635 &'Auto-Submitted:'& header lines are included. These are constructed according
22636 to the rules in RFCs 2822 and 3834, respectively.
22638 If the router that passes the message to this transport does not have the
22639 &%unseen%& option set, the original message (for the current recipient) is not
22640 delivered anywhere. However, when the &%unseen%& option is set on the router
22641 that passes the message to this transport, routing of the address continues, so
22642 another router can set up a normal message delivery.
22645 The &(autoreply)& transport is usually run as the result of mail filtering, a
22646 &"vacation"& message being the standard example. However, it can also be run
22647 directly from a router like any other transport. To reduce the possibility of
22648 message cascades, messages created by the &(autoreply)& transport always have
22649 empty envelope sender addresses, like bounce messages.
22651 The parameters of the message to be sent can be specified in the configuration
22652 by options described below. However, these are used only when the address
22653 passed to the transport does not contain its own reply information. When the
22654 transport is run as a consequence of a
22656 or &%vacation%& command in a filter file, the parameters of the message are
22657 supplied by the filter, and passed with the address. The transport's options
22658 that define the message are then ignored (so they are not usually set in this
22659 case). The message is specified entirely by the filter or by the transport; it
22660 is never built from a mixture of options. However, the &%file_optional%&,
22661 &%mode%&, and &%return_message%& options apply in all cases.
22663 &(Autoreply)& is implemented as a local transport. When used as a result of a
22664 command in a user's filter file, &(autoreply)& normally runs under the uid and
22665 gid of the user, and with appropriate current and home directories (see chapter
22666 &<<CHAPenvironment>>&).
22668 There is a subtle difference between routing a message to a &(pipe)& transport
22669 that generates some text to be returned to the sender, and routing it to an
22670 &(autoreply)& transport. This difference is noticeable only if more than one
22671 address from the same message is so handled. In the case of a pipe, the
22672 separate outputs from the different addresses are gathered up and returned to
22673 the sender in a single message, whereas if &(autoreply)& is used, a separate
22674 message is generated for each address that is passed to it.
22676 Non-printing characters are not permitted in the header lines generated for the
22677 message that &(autoreply)& creates, with the exception of newlines that are
22678 immediately followed by white space. If any non-printing characters are found,
22679 the transport defers.
22680 Whether characters with the top bit set count as printing characters or not is
22681 controlled by the &%print_topbitchars%& global option.
22683 If any of the generic options for manipulating headers (for example,
22684 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22685 of the original message that is included in the generated message when
22686 &%return_message%& is set. They do not apply to the generated message itself.
22688 .vindex "&$sender_address$&"
22689 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22690 the message, indicating that there were no recipients, it does not treat this
22691 as an error. This means that autoreplies sent to &$sender_address$& when this
22692 is empty (because the incoming message is a bounce message) do not cause
22693 problems. They are just discarded.
22697 .section "Private options for autoreply" "SECID139"
22698 .cindex "options" "&(autoreply)& transport"
22700 .option bcc autoreply string&!! unset
22701 This specifies the addresses that are to receive &"blind carbon copies"& of the
22702 message when the message is specified by the transport.
22705 .option cc autoreply string&!! unset
22706 This specifies recipients of the message and the contents of the &'Cc:'& header
22707 when the message is specified by the transport.
22710 .option file autoreply string&!! unset
22711 The contents of the file are sent as the body of the message when the message
22712 is specified by the transport. If both &%file%& and &%text%& are set, the text
22713 string comes first.
22716 .option file_expand autoreply boolean false
22717 If this is set, the contents of the file named by the &%file%& option are
22718 subjected to string expansion as they are added to the message.
22721 .option file_optional autoreply boolean false
22722 If this option is true, no error is generated if the file named by the &%file%&
22723 option or passed with the address does not exist or cannot be read.
22726 .option from autoreply string&!! unset
22727 This specifies the contents of the &'From:'& header when the message is
22728 specified by the transport.
22731 .option headers autoreply string&!! unset
22732 This specifies additional RFC 2822 headers that are to be added to the message
22733 when the message is specified by the transport. Several can be given by using
22734 &"\n"& to separate them. There is no check on the format.
22737 .option log autoreply string&!! unset
22738 This option names a file in which a record of every message sent is logged when
22739 the message is specified by the transport.
22742 .option mode autoreply "octal integer" 0600
22743 If either the log file or the &"once"& file has to be created, this mode is
22747 .option never_mail autoreply "address list&!!" unset
22748 If any run of the transport creates a message with a recipient that matches any
22749 item in the list, that recipient is quietly discarded. If all recipients are
22750 discarded, no message is created. This applies both when the recipients are
22751 generated by a filter and when they are specified in the transport.
22755 .option once autoreply string&!! unset
22756 This option names a file or DBM database in which a record of each &'To:'&
22757 recipient is kept when the message is specified by the transport. &*Note*&:
22758 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
22760 If &%once%& is unset, or is set to an empty string, the message is always sent.
22761 By default, if &%once%& is set to a non-empty file name, the message
22762 is not sent if a potential recipient is already listed in the database.
22763 However, if the &%once_repeat%& option specifies a time greater than zero, the
22764 message is sent if that much time has elapsed since a message was last sent to
22765 this recipient. A setting of zero time for &%once_repeat%& (the default)
22766 prevents a message from being sent a second time &-- in this case, zero means
22769 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
22770 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
22771 greater than zero, it changes the way Exim implements the &%once%& option.
22772 Instead of using a DBM file to record every recipient it sends to, it uses a
22773 regular file, whose size will never get larger than the given value.
22775 In the file, Exim keeps a linear list of recipient addresses and the times at
22776 which they were sent messages. If the file is full when a new address needs to
22777 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
22778 means that a given recipient may receive multiple messages, but at
22779 unpredictable intervals that depend on the rate of turnover of addresses in the
22780 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
22783 .option once_file_size autoreply integer 0
22784 See &%once%& above.
22787 .option once_repeat autoreply time&!! 0s
22788 See &%once%& above.
22789 After expansion, the value of this option must be a valid time value.
22792 .option reply_to autoreply string&!! unset
22793 This specifies the contents of the &'Reply-To:'& header when the message is
22794 specified by the transport.
22797 .option return_message autoreply boolean false
22798 If this is set, a copy of the original message is returned with the new
22799 message, subject to the maximum size set in the &%return_size_limit%& global
22800 configuration option.
22803 .option subject autoreply string&!! unset
22804 This specifies the contents of the &'Subject:'& header when the message is
22805 specified by the transport. It is tempting to quote the original subject in
22806 automatic responses. For example:
22808 subject = Re: $h_subject:
22810 There is a danger in doing this, however. It may allow a third party to
22811 subscribe your users to an opt-in mailing list, provided that the list accepts
22812 bounce messages as subscription confirmations. Well-managed lists require a
22813 non-bounce message to confirm a subscription, so the danger is relatively
22818 .option text autoreply string&!! unset
22819 This specifies a single string to be used as the body of the message when the
22820 message is specified by the transport. If both &%text%& and &%file%& are set,
22821 the text comes first.
22824 .option to autoreply string&!! unset
22825 This specifies recipients of the message and the contents of the &'To:'& header
22826 when the message is specified by the transport.
22827 .ecindex IIDauttra1
22828 .ecindex IIDauttra2
22833 . ////////////////////////////////////////////////////////////////////////////
22834 . ////////////////////////////////////////////////////////////////////////////
22836 .chapter "The lmtp transport" "CHAPLMTP"
22837 .cindex "transports" "&(lmtp)&"
22838 .cindex "&(lmtp)& transport"
22839 .cindex "LMTP" "over a pipe"
22840 .cindex "LMTP" "over a socket"
22841 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
22843 or by interacting with a Unix domain socket.
22844 This transport is something of a cross between the &(pipe)& and &(smtp)&
22845 transports. Exim also has support for using LMTP over TCP/IP; this is
22846 implemented as an option for the &(smtp)& transport. Because LMTP is expected
22847 to be of minority interest, the default build-time configure in &_src/EDITME_&
22848 has it commented out. You need to ensure that
22852 .cindex "options" "&(lmtp)& transport"
22853 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
22854 included in the Exim binary. The private options of the &(lmtp)& transport are
22857 .option batch_id lmtp string&!! unset
22858 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
22861 .option batch_max lmtp integer 1
22862 This limits the number of addresses that can be handled in a single delivery.
22863 Most LMTP servers can handle several addresses at once, so it is normally a
22864 good idea to increase this value. See the description of local delivery
22865 batching in chapter &<<CHAPbatching>>&.
22868 .option command lmtp string&!! unset
22869 This option must be set if &%socket%& is not set. The string is a command which
22870 is run in a separate process. It is split up into a command name and list of
22871 arguments, each of which is separately expanded (so expansion cannot change the
22872 number of arguments). The command is run directly, not via a shell. The message
22873 is passed to the new process using the standard input and output to operate the
22876 .option ignore_quota lmtp boolean false
22877 .cindex "LMTP" "ignoring quota errors"
22878 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
22879 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
22880 in its response to the LHLO command.
22882 .option socket lmtp string&!! unset
22883 This option must be set if &%command%& is not set. The result of expansion must
22884 be the name of a Unix domain socket. The transport connects to the socket and
22885 delivers the message to it using the LMTP protocol.
22888 .option timeout lmtp time 5m
22889 The transport is aborted if the created process or Unix domain socket does not
22890 respond to LMTP commands or message input within this timeout. Delivery
22891 is deferred, and will be tried again later. Here is an example of a typical
22896 command = /some/local/lmtp/delivery/program
22900 This delivers up to 20 addresses at a time, in a mixture of domains if
22901 necessary, running as the user &'exim'&.
22905 . ////////////////////////////////////////////////////////////////////////////
22906 . ////////////////////////////////////////////////////////////////////////////
22908 .chapter "The pipe transport" "CHAPpipetransport"
22909 .scindex IIDpiptra1 "transports" "&(pipe)&"
22910 .scindex IIDpiptra2 "&(pipe)& transport"
22911 The &(pipe)& transport is used to deliver messages via a pipe to a command
22912 running in another process. One example is the use of &(pipe)& as a
22913 pseudo-remote transport for passing messages to some other delivery mechanism
22914 (such as UUCP). Another is the use by individual users to automatically process
22915 their incoming messages. The &(pipe)& transport can be used in one of the
22919 .vindex "&$local_part$&"
22920 A router routes one address to a transport in the normal way, and the
22921 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
22922 contains the local part of the address (as usual), and the command that is run
22923 is specified by the &%command%& option on the transport.
22925 .vindex "&$pipe_addresses$&"
22926 If the &%batch_max%& option is set greater than 1 (the default is 1), the
22927 transport can handle more than one address in a single run. In this case, when
22928 more than one address is routed to the transport, &$local_part$& is not set
22929 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
22930 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
22931 that are routed to the transport.
22933 .vindex "&$address_pipe$&"
22934 A router redirects an address directly to a pipe command (for example, from an
22935 alias or forward file). In this case, &$address_pipe$& contains the text of the
22936 pipe command, and the &%command%& option on the transport is ignored unless
22937 &%force_command%& is set. If only one address is being transported
22938 (&%batch_max%& is not greater than one, or only one address was redirected to
22939 this pipe command), &$local_part$& contains the local part that was redirected.
22943 The &(pipe)& transport is a non-interactive delivery method. Exim can also
22944 deliver messages over pipes using the LMTP interactive protocol. This is
22945 implemented by the &(lmtp)& transport.
22947 In the case when &(pipe)& is run as a consequence of an entry in a local user's
22948 &_.forward_& file, the command runs under the uid and gid of that user. In
22949 other cases, the uid and gid have to be specified explicitly, either on the
22950 transport or on the router that handles the address. Current and &"home"&
22951 directories are also controllable. See chapter &<<CHAPenvironment>>& for
22952 details of the local delivery environment and chapter &<<CHAPbatching>>&
22953 for a discussion of local delivery batching.
22956 .section "Concurrent delivery" "SECID140"
22957 If two messages arrive at almost the same time, and both are routed to a pipe
22958 delivery, the two pipe transports may be run concurrently. You must ensure that
22959 any pipe commands you set up are robust against this happening. If the commands
22960 write to a file, the &%exim_lock%& utility might be of use.
22961 Alternatively the &%max_parallel%& option could be used with a value
22962 of "1" to enforce serialization.
22967 .section "Returned status and data" "SECID141"
22968 .cindex "&(pipe)& transport" "returned data"
22969 If the command exits with a non-zero return code, the delivery is deemed to
22970 have failed, unless either the &%ignore_status%& option is set (in which case
22971 the return code is treated as zero), or the return code is one of those listed
22972 in the &%temp_errors%& option, which are interpreted as meaning &"try again
22973 later"&. In this case, delivery is deferred. Details of a permanent failure are
22974 logged, but are not included in the bounce message, which merely contains
22975 &"local delivery failed"&.
22977 If the command exits on a signal and the &%freeze_signal%& option is set then
22978 the message will be frozen in the queue. If that option is not set, a bounce
22979 will be sent as normal.
22981 If the return code is greater than 128 and the command being run is a shell
22982 script, it normally means that the script was terminated by a signal whose
22983 value is the return code minus 128. The &%freeze_signal%& option does not
22984 apply in this case.
22986 If Exim is unable to run the command (that is, if &[execve()]& fails), the
22987 return code is set to 127. This is the value that a shell returns if it is
22988 asked to run a non-existent command. The wording for the log line suggests that
22989 a non-existent command may be the problem.
22991 The &%return_output%& option can affect the result of a pipe delivery. If it is
22992 set and the command produces any output on its standard output or standard
22993 error streams, the command is considered to have failed, even if it gave a zero
22994 return code or if &%ignore_status%& is set. The output from the command is
22995 included as part of the bounce message. The &%return_fail_output%& option is
22996 similar, except that output is returned only when the command exits with a
22997 failure return code, that is, a value other than zero or a code that matches
23002 .section "How the command is run" "SECThowcommandrun"
23003 .cindex "&(pipe)& transport" "path for command"
23004 The command line is (by default) broken down into a command name and arguments
23005 by the &(pipe)& transport itself. The &%allow_commands%& and
23006 &%restrict_to_path%& options can be used to restrict the commands that may be
23009 .cindex "quoting" "in pipe command"
23010 Unquoted arguments are delimited by white space. If an argument appears in
23011 double quotes, backslash is interpreted as an escape character in the usual
23012 way. If an argument appears in single quotes, no escaping is done.
23014 String expansion is applied to the command line except when it comes from a
23015 traditional &_.forward_& file (commands from a filter file are expanded). The
23016 expansion is applied to each argument in turn rather than to the whole line.
23017 For this reason, any string expansion item that contains white space must be
23018 quoted so as to be contained within a single argument. A setting such as
23020 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
23022 will not work, because the expansion item gets split between several
23023 arguments. You have to write
23025 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
23027 to ensure that it is all in one argument. The expansion is done in this way,
23028 argument by argument, so that the number of arguments cannot be changed as a
23029 result of expansion, and quotes or backslashes in inserted variables do not
23030 interact with external quoting. However, this leads to problems if you want to
23031 generate multiple arguments (or the command name plus arguments) from a single
23032 expansion. In this situation, the simplest solution is to use a shell. For
23035 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
23038 .cindex "transport" "filter"
23039 .cindex "filter" "transport filter"
23040 .vindex "&$pipe_addresses$&"
23041 Special handling takes place when an argument consists of precisely the text
23042 &`$pipe_addresses`&. This is not a general expansion variable; the only
23043 place this string is recognized is when it appears as an argument for a pipe or
23044 transport filter command. It causes each address that is being handled to be
23045 inserted in the argument list at that point &'as a separate argument'&. This
23046 avoids any problems with spaces or shell metacharacters, and is of use when a
23047 &(pipe)& transport is handling groups of addresses in a batch.
23049 If &%force_command%& is enabled on the transport, Special handling takes place
23050 for an argument that consists of precisely the text &`$address_pipe`&. It
23051 is handled similarly to &$pipe_addresses$& above. It is expanded and each
23052 argument is inserted in the argument list at that point
23053 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
23054 the only item in the argument; in fact, if it were then &%force_command%&
23055 should behave as a no-op. Rather, it should be used to adjust the command
23056 run while preserving the argument vector separation.
23058 After splitting up into arguments and expansion, the resulting command is run
23059 in a subprocess directly from the transport, &'not'& under a shell. The
23060 message that is being delivered is supplied on the standard input, and the
23061 standard output and standard error are both connected to a single pipe that is
23062 read by Exim. The &%max_output%& option controls how much output the command
23063 may produce, and the &%return_output%& and &%return_fail_output%& options
23064 control what is done with it.
23066 Not running the command under a shell (by default) lessens the security risks
23067 in cases when a command from a user's filter file is built out of data that was
23068 taken from an incoming message. If a shell is required, it can of course be
23069 explicitly specified as the command to be run. However, there are circumstances
23070 where existing commands (for example, in &_.forward_& files) expect to be run
23071 under a shell and cannot easily be modified. To allow for these cases, there is
23072 an option called &%use_shell%&, which changes the way the &(pipe)& transport
23073 works. Instead of breaking up the command line as just described, it expands it
23074 as a single string and passes the result to &_/bin/sh_&. The
23075 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
23076 with &%use_shell%&, and the whole mechanism is inherently less secure.
23080 .section "Environment variables" "SECTpipeenv"
23081 .cindex "&(pipe)& transport" "environment for command"
23082 .cindex "environment" "&(pipe)& transport"
23083 The environment variables listed below are set up when the command is invoked.
23084 This list is a compromise for maximum compatibility with other MTAs. Note that
23085 the &%environment%& option can be used to add additional variables to this
23086 environment. The environment for the &(pipe)& transport is not subject
23087 to the &%add_environment%& and &%keep_environment%& main config options.
23089 &`DOMAIN `& the domain of the address
23090 &`HOME `& the home directory, if set
23091 &`HOST `& the host name when called from a router (see below)
23092 &`LOCAL_PART `& see below
23093 &`LOCAL_PART_PREFIX `& see below
23094 &`LOCAL_PART_SUFFIX `& see below
23095 &`LOGNAME `& see below
23096 &`MESSAGE_ID `& Exim's local ID for the message
23097 &`PATH `& as specified by the &%path%& option below
23098 &`QUALIFY_DOMAIN `& the sender qualification domain
23099 &`RECIPIENT `& the complete recipient address
23100 &`SENDER `& the sender of the message (empty if a bounce)
23101 &`SHELL `& &`/bin/sh`&
23102 &`TZ `& the value of the &%timezone%& option, if set
23103 &`USER `& see below
23105 When a &(pipe)& transport is called directly from (for example) an &(accept)&
23106 router, LOCAL_PART is set to the local part of the address. When it is
23107 called as a result of a forward or alias expansion, LOCAL_PART is set to
23108 the local part of the address that was expanded. In both cases, any affixes are
23109 removed from the local part, and made available in LOCAL_PART_PREFIX and
23110 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
23111 same value as LOCAL_PART for compatibility with other MTAs.
23114 HOST is set only when a &(pipe)& transport is called from a router that
23115 associates hosts with an address, typically when using &(pipe)& as a
23116 pseudo-remote transport. HOST is set to the first host name specified by
23120 If the transport's generic &%home_directory%& option is set, its value is used
23121 for the HOME environment variable. Otherwise, a home directory may be set
23122 by the router's &%transport_home_directory%& option, which defaults to the
23123 user's home directory if &%check_local_user%& is set.
23126 .section "Private options for pipe" "SECID142"
23127 .cindex "options" "&(pipe)& transport"
23131 .option allow_commands pipe "string list&!!" unset
23132 .cindex "&(pipe)& transport" "permitted commands"
23133 The string is expanded, and is then interpreted as a colon-separated list of
23134 permitted commands. If &%restrict_to_path%& is not set, the only commands
23135 permitted are those in the &%allow_commands%& list. They need not be absolute
23136 paths; the &%path%& option is still used for relative paths. If
23137 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
23138 in the &%allow_commands%& list, or a name without any slashes that is found on
23139 the path. In other words, if neither &%allow_commands%& nor
23140 &%restrict_to_path%& is set, there is no restriction on the command, but
23141 otherwise only commands that are permitted by one or the other are allowed. For
23144 allow_commands = /usr/bin/vacation
23146 and &%restrict_to_path%& is not set, the only permitted command is
23147 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
23148 &%use_shell%& is set.
23151 .option batch_id pipe string&!! unset
23152 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23155 .option batch_max pipe integer 1
23156 This limits the number of addresses that can be handled in a single delivery.
23157 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23160 .option check_string pipe string unset
23161 As &(pipe)& writes the message, the start of each line is tested for matching
23162 &%check_string%&, and if it does, the initial matching characters are replaced
23163 by the contents of &%escape_string%&, provided both are set. The value of
23164 &%check_string%& is a literal string, not a regular expression, and the case of
23165 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
23166 of &%check_string%& and &%escape_string%& are forced to values that implement
23167 the SMTP escaping protocol. Any settings made in the configuration file are
23171 .option command pipe string&!! unset
23172 This option need not be set when &(pipe)& is being used to deliver to pipes
23173 obtained directly from address redirections. In other cases, the option must be
23174 set, to provide a command to be run. It need not yield an absolute path (see
23175 the &%path%& option below). The command is split up into separate arguments by
23176 Exim, and each argument is separately expanded, as described in section
23177 &<<SECThowcommandrun>>& above.
23180 .option environment pipe string&!! unset
23181 .cindex "&(pipe)& transport" "environment for command"
23182 .cindex "environment" "&(pipe)& transport"
23183 This option is used to add additional variables to the environment in which the
23184 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
23185 a string which is expanded, and then interpreted as a colon-separated list of
23186 environment settings of the form <&'name'&>=<&'value'&>.
23189 .option escape_string pipe string unset
23190 See &%check_string%& above.
23193 .option freeze_exec_fail pipe boolean false
23194 .cindex "exec failure"
23195 .cindex "failure of exec"
23196 .cindex "&(pipe)& transport" "failure of exec"
23197 Failure to exec the command in a pipe transport is by default treated like
23198 any other failure while running the command. However, if &%freeze_exec_fail%&
23199 is set, failure to exec is treated specially, and causes the message to be
23200 frozen, whatever the setting of &%ignore_status%&.
23203 .option freeze_signal pipe boolean false
23204 .cindex "signal exit"
23205 .cindex "&(pipe)& transport", "signal exit"
23206 Normally if the process run by a command in a pipe transport exits on a signal,
23207 a bounce message is sent. If &%freeze_signal%& is set, the message will be
23208 frozen in Exim's queue instead.
23211 .option force_command pipe boolean false
23212 .cindex "force command"
23213 .cindex "&(pipe)& transport", "force command"
23214 Normally when a router redirects an address directly to a pipe command
23215 the &%command%& option on the transport is ignored. If &%force_command%&
23216 is set, the &%command%& option will used. This is especially
23217 useful for forcing a wrapper or additional argument to be added to the
23218 command. For example:
23220 command = /usr/bin/remote_exec myhost -- $address_pipe
23224 Note that &$address_pipe$& is handled specially in &%command%& when
23225 &%force_command%& is set, expanding out to the original argument vector as
23226 separate items, similarly to a Unix shell &`"$@"`& construct.
23229 .option ignore_status pipe boolean false
23230 If this option is true, the status returned by the subprocess that is set up to
23231 run the command is ignored, and Exim behaves as if zero had been returned.
23232 Otherwise, a non-zero status or termination by signal causes an error return
23233 from the transport unless the status value is one of those listed in
23234 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23236 &*Note*&: This option does not apply to timeouts, which do not return a status.
23237 See the &%timeout_defer%& option for how timeouts are handled.
23240 .option log_defer_output pipe boolean false
23241 .cindex "&(pipe)& transport" "logging output"
23242 If this option is set, and the status returned by the command is
23243 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23244 and any output was produced on stdout or stderr, the first line of it is
23245 written to the main log.
23248 .option log_fail_output pipe boolean false
23249 If this option is set, and the command returns any output on stdout or
23250 stderr, and also ends with a return code that is neither zero nor one of
23251 the return codes listed in &%temp_errors%& (that is, the delivery
23252 failed), the first line of output is written to the main log. This
23253 option and &%log_output%& are mutually exclusive. Only one of them may
23257 .option log_output pipe boolean false
23258 If this option is set and the command returns any output on stdout or
23259 stderr, the first line of output is written to the main log, whatever
23260 the return code. This option and &%log_fail_output%& are mutually
23261 exclusive. Only one of them may be set.
23264 .option max_output pipe integer 20K
23265 This specifies the maximum amount of output that the command may produce on its
23266 standard output and standard error file combined. If the limit is exceeded, the
23267 process running the command is killed. This is intended as a safety measure to
23268 catch runaway processes. The limit is applied independently of the settings of
23269 the options that control what is done with such output (for example,
23270 &%return_output%&). Because of buffering effects, the amount of output may
23271 exceed the limit by a small amount before Exim notices.
23274 .option message_prefix pipe string&!! "see below"
23275 The string specified here is expanded and output at the start of every message.
23276 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23279 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23283 .cindex "&%tmail%&"
23284 .cindex "&""From""& line"
23285 This is required by the commonly used &_/usr/bin/vacation_& program.
23286 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23287 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23292 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23293 &`\n`& to &`\r\n`& in &%message_prefix%&.
23296 .option message_suffix pipe string&!! "see below"
23297 The string specified here is expanded and output at the end of every message.
23298 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23299 The suffix can be suppressed by setting
23303 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23304 &`\n`& to &`\r\n`& in &%message_suffix%&.
23307 .option path pipe string&!! "/bin:/usr/bin"
23308 This option is expanded and
23309 specifies the string that is set up in the PATH environment
23310 variable of the subprocess.
23311 If the &%command%& option does not yield an absolute path name, the command is
23312 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23313 apply to a command specified as a transport filter.
23316 .option permit_coredump pipe boolean false
23317 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23318 a core-dump of a pipe command, enable this command. This enables core-dumps
23319 during delivery and affects both the Exim binary and the pipe command run.
23320 It is recommended that this option remain off unless and until you have a need
23321 for it and that this only be enabled when needed, as the risk of excessive
23322 resource consumption can be quite high. Note also that Exim is typically
23323 installed as a setuid binary and most operating systems will inhibit coredumps
23324 of these by default, so further OS-specific action may be required.
23327 .option pipe_as_creator pipe boolean false
23328 .cindex "uid (user id)" "local delivery"
23329 If the generic &%user%& option is not set and this option is true, the delivery
23330 process is run under the uid that was in force when Exim was originally called
23331 to accept the message. If the group id is not otherwise set (via the generic
23332 &%group%& option), the gid that was in force when Exim was originally called to
23333 accept the message is used.
23336 .option restrict_to_path pipe boolean false
23337 When this option is set, any command name not listed in &%allow_commands%& must
23338 contain no slashes. The command is searched for only in the directories listed
23339 in the &%path%& option. This option is intended for use in the case when a pipe
23340 command has been generated from a user's &_.forward_& file. This is usually
23341 handled by a &(pipe)& transport called &%address_pipe%&.
23344 .option return_fail_output pipe boolean false
23345 If this option is true, and the command produced any output and ended with a
23346 return code other than zero or one of the codes listed in &%temp_errors%& (that
23347 is, the delivery failed), the output is returned in the bounce message.
23348 However, if the message has a null sender (that is, it is itself a bounce
23349 message), output from the command is discarded. This option and
23350 &%return_output%& are mutually exclusive. Only one of them may be set.
23354 .option return_output pipe boolean false
23355 If this option is true, and the command produced any output, the delivery is
23356 deemed to have failed whatever the return code from the command, and the output
23357 is returned in the bounce message. Otherwise, the output is just discarded.
23358 However, if the message has a null sender (that is, it is a bounce message),
23359 output from the command is always discarded, whatever the setting of this
23360 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23361 of them may be set.
23365 .option temp_errors pipe "string list" "see below"
23366 .cindex "&(pipe)& transport" "temporary failure"
23367 This option contains either a colon-separated list of numbers, or a single
23368 asterisk. If &%ignore_status%& is false
23369 and &%return_output%& is not set,
23370 and the command exits with a non-zero return code, the failure is treated as
23371 temporary and the delivery is deferred if the return code matches one of the
23372 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23373 codes are treated as permanent errors. The default setting contains the codes
23374 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23375 compiled on a system that does not define these macros, it assumes values of 75
23376 and 73, respectively.
23379 .option timeout pipe time 1h
23380 If the command fails to complete within this time, it is killed. This normally
23381 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23382 specifies no timeout. In order to ensure that any subprocesses created by the
23383 command are also killed, Exim makes the initial process a process group leader,
23384 and kills the whole process group on a timeout. However, this can be defeated
23385 if one of the processes starts a new process group.
23387 .option timeout_defer pipe boolean false
23388 A timeout in a &(pipe)& transport, either in the command that the transport
23389 runs, or in a transport filter that is associated with it, is by default
23390 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23391 is set true, both kinds of timeout become temporary errors, causing the
23392 delivery to be deferred.
23394 .option umask pipe "octal integer" 022
23395 This specifies the umask setting for the subprocess that runs the command.
23398 .option use_bsmtp pipe boolean false
23399 .cindex "envelope sender"
23400 If this option is set true, the &(pipe)& transport writes messages in &"batch
23401 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23402 commands. If you want to include a leading HELO command with such messages,
23403 you can do so by setting the &%message_prefix%& option. See section
23404 &<<SECTbatchSMTP>>& for details of batch SMTP.
23406 .option use_classresources pipe boolean false
23407 .cindex "class resources (BSD)"
23408 This option is available only when Exim is running on FreeBSD, NetBSD, or
23409 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23410 resource limits when a &(pipe)& transport is run to perform a delivery. The
23411 limits for the uid under which the pipe is to run are obtained from the login
23415 .option use_crlf pipe boolean false
23416 .cindex "carriage return"
23418 This option causes lines to be terminated with the two-character CRLF sequence
23419 (carriage return, linefeed) instead of just a linefeed character. In the case
23420 of batched SMTP, the byte sequence written to the pipe is then an exact image
23421 of what would be sent down a real SMTP connection.
23423 The contents of the &%message_prefix%& and &%message_suffix%& options are
23424 written verbatim, so must contain their own carriage return characters if these
23425 are needed. When &%use_bsmtp%& is not set, the default values for both
23426 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23427 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23430 .option use_shell pipe boolean false
23431 .vindex "&$pipe_addresses$&"
23432 If this option is set, it causes the command to be passed to &_/bin/sh_&
23433 instead of being run directly from the transport, as described in section
23434 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23435 where the command is expected to be run under a shell and cannot easily be
23436 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23437 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23438 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23443 .section "Using an external local delivery agent" "SECID143"
23444 .cindex "local delivery" "using an external agent"
23445 .cindex "&'procmail'&"
23446 .cindex "external local delivery"
23447 .cindex "delivery" "&'procmail'&"
23448 .cindex "delivery" "by external agent"
23449 The &(pipe)& transport can be used to pass all messages that require local
23450 delivery to a separate local delivery agent such as &%procmail%&. When doing
23451 this, care must be taken to ensure that the pipe is run under an appropriate
23452 uid and gid. In some configurations one wants this to be a uid that is trusted
23453 by the delivery agent to supply the correct sender of the message. It may be
23454 necessary to recompile or reconfigure the delivery agent so that it trusts an
23455 appropriate user. The following is an example transport and router
23456 configuration for &%procmail%&:
23461 command = /usr/local/bin/procmail -d $local_part
23465 check_string = "From "
23466 escape_string = ">From "
23475 transport = procmail_pipe
23477 In this example, the pipe is run as the local user, but with the group set to
23478 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23479 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23480 user to supply a correct sender address. If you do not specify either a
23481 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23482 home directory is the user's home directory by default.
23484 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23488 as shown in some &%procmail%& documentation, because Exim does not by default
23489 use a shell to run pipe commands.
23492 The next example shows a transport and a router for a system where local
23493 deliveries are handled by the Cyrus IMAP server.
23496 local_delivery_cyrus:
23498 command = /usr/cyrus/bin/deliver \
23499 -m ${substr_1:$local_part_suffix} -- $local_part
23511 local_part_suffix = .*
23512 transport = local_delivery_cyrus
23514 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23515 &%return_output%& to cause any text written by Cyrus to be returned to the
23517 .ecindex IIDpiptra1
23518 .ecindex IIDpiptra2
23521 . ////////////////////////////////////////////////////////////////////////////
23522 . ////////////////////////////////////////////////////////////////////////////
23524 .chapter "The smtp transport" "CHAPsmtptrans"
23525 .scindex IIDsmttra1 "transports" "&(smtp)&"
23526 .scindex IIDsmttra2 "&(smtp)& transport"
23527 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23528 or LMTP protocol. The list of hosts to try can either be taken from the address
23529 that is being processed (having been set up by the router), or specified
23530 explicitly for the transport. Timeout and retry processing (see chapter
23531 &<<CHAPretry>>&) is applied to each IP address independently.
23534 .section "Multiple messages on a single connection" "SECID144"
23535 The sending of multiple messages over a single TCP/IP connection can arise in
23539 If a message contains more than &%max_rcpt%& (see below) addresses that are
23540 routed to the same host, more than one copy of the message has to be sent to
23541 that host. In this situation, multiple copies may be sent in a single run of
23542 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23543 does when it has too many addresses to send in one message also depends on the
23544 value of the global &%remote_max_parallel%& option. Details are given in
23545 section &<<SECToutSMTPTCP>>&.)
23547 .cindex "hints database" "remembering routing"
23548 When a message has been successfully delivered over a TCP/IP connection, Exim
23549 looks in its hints database to see if there are any other messages awaiting a
23550 connection to the same host. If there are, a new delivery process is started
23551 for one of them, and the current TCP/IP connection is passed on to it. The new
23552 process may in turn send multiple copies and possibly create yet another
23557 For each copy sent over the same TCP/IP connection, a sequence counter is
23558 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23559 no further messages are sent over that connection.
23563 .section "Use of the $host and $host_address variables" "SECID145"
23565 .vindex "&$host_address$&"
23566 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23567 &$host_address$& are the name and IP address of the first host on the host list
23568 passed by the router. However, when the transport is about to connect to a
23569 specific host, and while it is connected to that host, &$host$& and
23570 &$host_address$& are set to the values for that host. These are the values
23571 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23572 &%serialize_hosts%&, and the various TLS options are expanded.
23575 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23576 .vindex &$tls_bits$&
23577 .vindex &$tls_cipher$&
23578 .vindex &$tls_peerdn$&
23579 .vindex &$tls_sni$&
23580 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23581 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23582 are the values that were set when the message was received.
23583 These are the values that are used for options that are expanded before any
23584 SMTP connections are made. Just before each connection is made, these four
23585 variables are emptied. If TLS is subsequently started, they are set to the
23586 appropriate values for the outgoing connection, and these are the values that
23587 are in force when any authenticators are run and when the
23588 &%authenticated_sender%& option is expanded.
23590 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23591 and will be removed in a future release.
23594 .section "Private options for smtp" "SECID146"
23595 .cindex "options" "&(smtp)& transport"
23596 The private options of the &(smtp)& transport are as follows:
23599 .option address_retry_include_sender smtp boolean true
23600 .cindex "4&'xx'& responses" "retrying after"
23601 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23602 is the combination of sender and recipient that is delayed in subsequent queue
23603 runs until the retry time is reached. You can delay the recipient without
23604 reference to the sender (which is what earlier versions of Exim did), by
23605 setting &%address_retry_include_sender%& false. However, this can lead to
23606 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23608 .option allow_localhost smtp boolean false
23609 .cindex "local host" "sending to"
23610 .cindex "fallback" "hosts specified on transport"
23611 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23612 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23613 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23614 the delivery anyway. This should be used only in special cases when the
23615 configuration ensures that no looping will result (for example, a differently
23616 configured Exim is listening on the port to which the message is sent).
23619 .option authenticated_sender smtp string&!! unset
23621 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23622 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23623 overriding any existing authenticated sender value. If the string expansion is
23624 forced to fail, the option is ignored. Other expansion failures cause delivery
23625 to be deferred. If the result of expansion is an empty string, that is also
23628 The expansion happens after the outgoing connection has been made and TLS
23629 started, if required. This means that the &$host$&, &$host_address$&,
23630 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23631 particular connection.
23633 If the SMTP session is not authenticated, the expansion of
23634 &%authenticated_sender%& still happens (and can cause the delivery to be
23635 deferred if it fails), but no AUTH= item is added to MAIL commands
23636 unless &%authenticated_sender_force%& is true.
23638 This option allows you to use the &(smtp)& transport in LMTP mode to
23639 deliver mail to Cyrus IMAP and provide the proper local part as the
23640 &"authenticated sender"&, via a setting such as:
23642 authenticated_sender = $local_part
23644 This removes the need for IMAP subfolders to be assigned special ACLs to
23645 allow direct delivery to those subfolders.
23647 Because of expected uses such as that just described for Cyrus (when no
23648 domain is involved), there is no checking on the syntax of the provided
23652 .option authenticated_sender_force smtp boolean false
23653 If this option is set true, the &%authenticated_sender%& option's value
23654 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23655 authenticated as a client.
23658 .option command_timeout smtp time 5m
23659 This sets a timeout for receiving a response to an SMTP command that has been
23660 sent out. It is also used when waiting for the initial banner line from the
23661 remote host. Its value must not be zero.
23664 .option connect_timeout smtp time 5m
23665 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23666 to a remote host. A setting of zero allows the system timeout (typically
23667 several minutes) to act. To have any effect, the value of this option must be
23668 less than the system timeout. However, it has been observed that on some
23669 systems there is no system timeout, which is why the default value for this
23670 option is 5 minutes, a value recommended by RFC 1123.
23673 .option connection_max_messages smtp integer 500
23674 .cindex "SMTP" "passed connection"
23675 .cindex "SMTP" "multiple deliveries"
23676 .cindex "multiple SMTP deliveries"
23677 This controls the maximum number of separate message deliveries that are sent
23678 over a single TCP/IP connection. If the value is zero, there is no limit.
23679 For testing purposes, this value can be overridden by the &%-oB%& command line
23683 .option data_timeout smtp time 5m
23684 This sets a timeout for the transmission of each block in the data portion of
23685 the message. As a result, the overall timeout for a message depends on the size
23686 of the message. Its value must not be zero. See also &%final_timeout%&.
23689 .option dkim_domain smtp string&!! unset
23690 .option dkim_selector smtp string&!! unset
23691 .option dkim_private_key smtp string&!! unset
23692 .option dkim_canon smtp string&!! unset
23693 .option dkim_strict smtp string&!! unset
23694 .option dkim_sign_headers smtp string&!! unset
23695 DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
23698 .option delay_after_cutoff smtp boolean true
23699 This option controls what happens when all remote IP addresses for a given
23700 domain have been inaccessible for so long that they have passed their retry
23703 In the default state, if the next retry time has not been reached for any of
23704 them, the address is bounced without trying any deliveries. In other words,
23705 Exim delays retrying an IP address after the final cutoff time until a new
23706 retry time is reached, and can therefore bounce an address without ever trying
23707 a delivery, when machines have been down for a long time. Some people are
23708 unhappy at this prospect, so...
23710 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
23711 addresses are past their final cutoff time, Exim tries to deliver to those
23712 IP addresses that have not been tried since the message arrived. If there are
23713 none, of if they all fail, the address is bounced. In other words, it does not
23714 delay when a new message arrives, but immediately tries those expired IP
23715 addresses that haven't been tried since the message arrived. If there is a
23716 continuous stream of messages for the dead hosts, unsetting
23717 &%delay_after_cutoff%& means that there will be many more attempts to deliver
23721 .option dns_qualify_single smtp boolean true
23722 If the &%hosts%& or &%fallback_hosts%& option is being used,
23723 and the &%gethostbyname%& option is false,
23724 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
23725 in chapter &<<CHAPdnslookup>>& for more details.
23728 .option dns_search_parents smtp boolean false
23729 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
23730 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
23731 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
23735 .option dnssec_request_domains smtp "domain list&!!" unset
23736 .cindex "MX record" "security"
23737 .cindex "DNSSEC" "MX lookup"
23738 .cindex "security" "MX lookup"
23739 .cindex "DNS" "DNSSEC"
23740 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
23741 the dnssec request bit set.
23742 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23746 .option dnssec_require_domains smtp "domain list&!!" unset
23747 .cindex "MX record" "security"
23748 .cindex "DNSSEC" "MX lookup"
23749 .cindex "security" "MX lookup"
23750 .cindex "DNS" "DNSSEC"
23751 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
23752 the dnssec request bit set. Any returns not having the Authenticated Data bit
23753 (AD bit) set will be ignored and logged as a host-lookup failure.
23754 This applies to all of the SRV, MX, AAAA, A lookup sequence.
23758 .option dscp smtp string&!! unset
23759 .cindex "DCSP" "outbound"
23760 This option causes the DSCP value associated with a socket to be set to one
23761 of a number of fixed strings or to numeric value.
23762 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
23763 Common values include &`throughput`&, &`mincost`&, and on newer systems
23764 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
23766 The outbound packets from Exim will be marked with this value in the header
23767 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
23768 that these values will have any effect, not be stripped by networking
23769 equipment, or do much of anything without cooperation with your Network
23770 Engineer and those of all network operators between the source and destination.
23773 .option fallback_hosts smtp "string list" unset
23774 .cindex "fallback" "hosts specified on transport"
23775 String expansion is not applied to this option. The argument must be a
23776 colon-separated list of host names or IP addresses, optionally also including
23777 port numbers, though the separator can be changed, as described in section
23778 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23779 item in a &%route_list%& setting for the &(manualroute)& router, as described
23780 in section &<<SECTformatonehostitem>>&.
23782 Fallback hosts can also be specified on routers, which associate them with the
23783 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
23784 &%fallback_hosts%& specified on the transport is used only if the address does
23785 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
23786 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
23787 However, &%hosts_randomize%& does apply to fallback host lists.
23789 If Exim is unable to deliver to any of the hosts for a particular address, and
23790 the errors are not permanent rejections, the address is put on a separate
23791 transport queue with its host list replaced by the fallback hosts, unless the
23792 address was routed via MX records and the current host was in the original MX
23793 list. In that situation, the fallback host list is not used.
23795 Once normal deliveries are complete, the fallback queue is delivered by
23796 re-running the same transports with the new host lists. If several failing
23797 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
23798 copy of the message is sent.
23800 The resolution of the host names on the fallback list is controlled by the
23801 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
23802 both to cases when the host list comes with the address and when it is taken
23803 from &%hosts%&. This option provides a &"use a smart host only if delivery
23807 .option final_timeout smtp time 10m
23808 This is the timeout that applies while waiting for the response to the final
23809 line containing just &"."& that terminates a message. Its value must not be
23812 .option gethostbyname smtp boolean false
23813 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
23814 being used, names are looked up using &[gethostbyname()]&
23815 (or &[getipnodebyname()]& when available)
23816 instead of using the DNS. Of course, that function may in fact use the DNS, but
23817 it may also consult other sources of information such as &_/etc/hosts_&.
23819 .option gnutls_compat_mode smtp boolean unset
23820 This option controls whether GnuTLS is used in compatibility mode in an Exim
23821 server. This reduces security slightly, but improves interworking with older
23822 implementations of TLS.
23824 .option helo_data smtp string&!! "see below"
23825 .cindex "HELO" "argument, setting"
23826 .cindex "EHLO" "argument, setting"
23827 .cindex "LHLO argument setting"
23828 The value of this option is expanded after a connection to a another host has
23829 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
23830 command that starts the outgoing SMTP or LMTP session. The default value of the
23835 During the expansion, the variables &$host$& and &$host_address$& are set to
23836 the identity of the remote host, and the variables &$sending_ip_address$& and
23837 &$sending_port$& are set to the local IP address and port number that are being
23838 used. These variables can be used to generate different values for different
23839 servers or different local IP addresses. For example, if you want the string
23840 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
23841 interface address, you could use this:
23843 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
23844 {$primary_hostname}}
23846 The use of &%helo_data%& applies both to sending messages and when doing
23849 .option hosts smtp "string list&!!" unset
23850 Hosts are associated with an address by a router such as &(dnslookup)&, which
23851 finds the hosts by looking up the address domain in the DNS, or by
23852 &(manualroute)&, which has lists of hosts in its configuration. However,
23853 email addresses can be passed to the &(smtp)& transport by any router, and not
23854 all of them can provide an associated list of hosts.
23856 The &%hosts%& option specifies a list of hosts to be used if the address being
23857 processed does not have any hosts associated with it. The hosts specified by
23858 &%hosts%& are also used, whether or not the address has its own hosts, if
23859 &%hosts_override%& is set.
23861 The string is first expanded, before being interpreted as a colon-separated
23862 list of host names or IP addresses, possibly including port numbers. The
23863 separator may be changed to something other than colon, as described in section
23864 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
23865 item in a &%route_list%& setting for the &(manualroute)& router, as described
23866 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
23867 of the &(manualroute)& router is not available here.
23869 If the expansion fails, delivery is deferred. Unless the failure was caused by
23870 the inability to complete a lookup, the error is logged to the panic log as
23871 well as the main log. Host names are looked up either by searching directly for
23872 address records in the DNS or by calling &[gethostbyname()]& (or
23873 &[getipnodebyname()]& when available), depending on the setting of the
23874 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
23875 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
23878 During delivery, the hosts are tried in order, subject to their retry status,
23879 unless &%hosts_randomize%& is set.
23882 .option hosts_avoid_esmtp smtp "host list&!!" unset
23883 .cindex "ESMTP, avoiding use of"
23884 .cindex "HELO" "forcing use of"
23885 .cindex "EHLO" "avoiding use of"
23886 .cindex "PIPELINING" "avoiding the use of"
23887 This option is for use with broken hosts that announce ESMTP facilities (for
23888 example, PIPELINING) and then fail to implement them properly. When a host
23889 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
23890 start of the SMTP session. This means that it cannot use any of the ESMTP
23891 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
23894 .option hosts_avoid_pipelining smtp "host list&!!" unset
23895 .cindex "PIPELINING" "avoiding the use of"
23896 Exim will not use the SMTP PIPELINING extension when delivering to any host
23897 that matches this list, even if the server host advertises PIPELINING support.
23900 .option hosts_avoid_tls smtp "host list&!!" unset
23901 .cindex "TLS" "avoiding for certain hosts"
23902 Exim will not try to start a TLS session when delivering to any host that
23903 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23905 .option hosts_verify_avoid_tls smtp "host list&!!" unset
23906 .cindex "TLS" "avoiding for certain hosts"
23907 Exim will not try to start a TLS session for a verify callout,
23908 or when delivering in cutthrough mode,
23909 to any host that matches this list.
23912 .option hosts_max_try smtp integer 5
23913 .cindex "host" "maximum number to try"
23914 .cindex "limit" "number of hosts tried"
23915 .cindex "limit" "number of MX tried"
23916 .cindex "MX record" "maximum tried"
23917 This option limits the number of IP addresses that are tried for any one
23918 delivery in cases where there are temporary delivery errors. Section
23919 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
23922 .option hosts_max_try_hardlimit smtp integer 50
23923 This is an additional check on the maximum number of IP addresses that Exim
23924 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
23929 .option hosts_nopass_tls smtp "host list&!!" unset
23930 .cindex "TLS" "passing connection"
23931 .cindex "multiple SMTP deliveries"
23932 .cindex "TLS" "multiple message deliveries"
23933 For any host that matches this list, a connection on which a TLS session has
23934 been started will not be passed to a new delivery process for sending another
23935 message on the same connection. See section &<<SECTmulmessam>>& for an
23936 explanation of when this might be needed.
23939 .option hosts_override smtp boolean false
23940 If this option is set and the &%hosts%& option is also set, any hosts that are
23941 attached to the address are ignored, and instead the hosts specified by the
23942 &%hosts%& option are always used. This option does not apply to
23943 &%fallback_hosts%&.
23946 .option hosts_randomize smtp boolean false
23947 .cindex "randomized host list"
23948 .cindex "host" "list of; randomized"
23949 .cindex "fallback" "randomized hosts"
23950 If this option is set, and either the list of hosts is taken from the
23951 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
23952 were not obtained from MX records (this includes fallback hosts from the
23953 router), and were not randomized by the router, the order of trying the hosts
23954 is randomized each time the transport runs. Randomizing the order of a host
23955 list can be used to do crude load sharing.
23957 When &%hosts_randomize%& is true, a host list may be split into groups whose
23958 order is separately randomized. This makes it possible to set up MX-like
23959 behaviour. The boundaries between groups are indicated by an item that is just
23960 &`+`& in the host list. For example:
23962 hosts = host1:host2:host3:+:host4:host5
23964 The order of the first three hosts and the order of the last two hosts is
23965 randomized for each use, but the first three always end up before the last two.
23966 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
23968 .option hosts_require_auth smtp "host list&!!" unset
23969 .cindex "authentication" "required by client"
23970 This option provides a list of servers for which authentication must succeed
23971 before Exim will try to transfer a message. If authentication fails for
23972 servers which are not in this list, Exim tries to send unauthenticated. If
23973 authentication fails for one of these servers, delivery is deferred. This
23974 temporary error is detectable in the retry rules, so it can be turned into a
23975 hard failure if required. See also &%hosts_try_auth%&, and chapter
23976 &<<CHAPSMTPAUTH>>& for details of authentication.
23979 .option hosts_request_ocsp smtp "host list&!!" *
23980 .cindex "TLS" "requiring for certain servers"
23981 Exim will request a Certificate Status on a
23982 TLS session for any host that matches this list.
23983 &%tls_verify_certificates%& should also be set for the transport.
23985 .option hosts_require_ocsp smtp "host list&!!" unset
23986 .cindex "TLS" "requiring for certain servers"
23987 Exim will request, and check for a valid Certificate Status being given, on a
23988 TLS session for any host that matches this list.
23989 &%tls_verify_certificates%& should also be set for the transport.
23991 .option hosts_require_tls smtp "host list&!!" unset
23992 .cindex "TLS" "requiring for certain servers"
23993 Exim will insist on using a TLS session when delivering to any host that
23994 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
23995 &*Note*&: This option affects outgoing mail only. To insist on TLS for
23996 incoming messages, use an appropriate ACL.
23998 .option hosts_try_auth smtp "host list&!!" unset
23999 .cindex "authentication" "optional in client"
24000 This option provides a list of servers to which, provided they announce
24001 authentication support, Exim will attempt to authenticate as a client when it
24002 connects. If authentication fails, Exim will try to transfer the message
24003 unauthenticated. See also &%hosts_require_auth%&, and chapter
24004 &<<CHAPSMTPAUTH>>& for details of authentication.
24006 .option hosts_try_chunking smtp "host list&!!" *
24007 .cindex CHUNKING "enabling, in client"
24008 .cindex BDAT "SMTP command"
24009 .cindex "RFC 3030" "CHUNKING"
24010 This option provides a list of servers to which, provided they announce
24011 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
24012 BDAT will not be used in conjunction with a transport filter.
24014 .option hosts_try_fastopen smtp "host list!!" unset
24015 .cindex "fast open, TCP" "enabling, in client"
24016 .cindex "TCP Fast Open" "enabling, in client"
24017 .cindex "RFC 7413" "TCP Fast Open"
24018 This option provides a list of servers to which, provided
24019 the facility is supported by this system, Exim will attempt to
24020 perform a TCP Fast Open.
24021 No data is sent on the SYN segment but, if the remote server also
24022 supports the facility, it can send its SMTP banner immediately after
24023 the SYN,ACK segment. This can save up to one round-trip time.
24025 The facility is only active for previously-contacted servers,
24026 as the initiator must present a cookie in the SYN segment.
24028 On (at least some) current Linux distributions the facility must be enabled
24029 in the kernel by the sysadmin before the support is usable.
24031 .option hosts_try_prdr smtp "host list&!!" *
24032 .cindex "PRDR" "enabling, optional in client"
24033 This option provides a list of servers to which, provided they announce
24034 PRDR support, Exim will attempt to negotiate PRDR
24035 for multi-recipient messages.
24036 The option can usually be left as default.
24038 .option interface smtp "string list&!!" unset
24039 .cindex "bind IP address"
24040 .cindex "IP address" "binding"
24042 .vindex "&$host_address$&"
24043 This option specifies which interface to bind to when making an outgoing SMTP
24044 call. The value is an IP address, not an interface name such as
24045 &`eth0`&. Do not confuse this with the interface address that was used when a
24046 message was received, which is in &$received_ip_address$&, formerly known as
24047 &$interface_address$&. The name was changed to minimize confusion with the
24048 outgoing interface address. There is no variable that contains an outgoing
24049 interface address because, unless it is set by this option, its value is
24052 During the expansion of the &%interface%& option the variables &$host$& and
24053 &$host_address$& refer to the host to which a connection is about to be made
24054 during the expansion of the string. Forced expansion failure, or an empty
24055 string result causes the option to be ignored. Otherwise, after expansion, the
24056 string must be a list of IP addresses, colon-separated by default, but the
24057 separator can be changed in the usual way. For example:
24059 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
24061 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
24062 connection. If none of them are the correct type, the option is ignored. If
24063 &%interface%& is not set, or is ignored, the system's IP functions choose which
24064 interface to use if the host has more than one.
24067 .option keepalive smtp boolean true
24068 .cindex "keepalive" "on outgoing connection"
24069 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
24070 connections. When set, it causes the kernel to probe idle connections
24071 periodically, by sending packets with &"old"& sequence numbers. The other end
24072 of the connection should send a acknowledgment if the connection is still okay
24073 or a reset if the connection has been aborted. The reason for doing this is
24074 that it has the beneficial effect of freeing up certain types of connection
24075 that can get stuck when the remote host is disconnected without tidying up the
24076 TCP/IP call properly. The keepalive mechanism takes several hours to detect
24080 .option lmtp_ignore_quota smtp boolean false
24081 .cindex "LMTP" "ignoring quota errors"
24082 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
24083 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
24084 has advertised support for IGNOREQUOTA in its response to the LHLO command.
24086 .option max_rcpt smtp integer 100
24087 .cindex "RCPT" "maximum number of outgoing"
24088 This option limits the number of RCPT commands that are sent in a single
24089 SMTP message transaction. Each set of addresses is treated independently, and
24090 so can cause parallel connections to the same host if &%remote_max_parallel%&
24094 .option multi_domain smtp boolean&!! true
24095 .vindex "&$domain$&"
24096 When this option is set, the &(smtp)& transport can handle a number of
24097 addresses containing a mixture of different domains provided they all resolve
24098 to the same list of hosts. Turning the option off restricts the transport to
24099 handling only one domain at a time. This is useful if you want to use
24100 &$domain$& in an expansion for the transport, because it is set only when there
24101 is a single domain involved in a remote delivery.
24103 It is expanded per-address and can depend on any of
24104 &$address_data$&, &$domain_data$&, &$local_part_data$&,
24105 &$host$&, &$host_address$& and &$host_port$&.
24107 .option port smtp string&!! "see below"
24108 .cindex "port" "sending TCP/IP"
24109 .cindex "TCP/IP" "setting outgoing port"
24110 This option specifies the TCP/IP port on the server to which Exim connects.
24111 &*Note:*& Do not confuse this with the port that was used when a message was
24112 received, which is in &$received_port$&, formerly known as &$interface_port$&.
24113 The name was changed to minimize confusion with the outgoing port. There is no
24114 variable that contains an outgoing port.
24116 If the value of this option begins with a digit it is taken as a port number;
24117 otherwise it is looked up using &[getservbyname()]&. The default value is
24118 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
24119 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
24124 .option protocol smtp string smtp
24125 .cindex "LMTP" "over TCP/IP"
24126 .cindex "ssmtp protocol" "outbound"
24127 .cindex "TLS" "SSL-on-connect outbound"
24129 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
24130 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
24131 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
24132 deliveries into closed message stores. Exim also has support for running LMTP
24133 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
24135 If this option is set to &"smtps"&, the default value for the &%port%& option
24136 changes to &"smtps"&, and the transport initiates TLS immediately after
24137 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
24138 The Internet standards bodies strongly discourage use of this mode.
24141 .option retry_include_ip_address smtp boolean&!! true
24142 Exim normally includes both the host name and the IP address in the key it
24143 constructs for indexing retry data after a temporary delivery failure. This
24144 means that when one of several IP addresses for a host is failing, it gets
24145 tried periodically (controlled by the retry rules), but use of the other IP
24146 addresses is not affected.
24148 However, in some dialup environments hosts are assigned a different IP address
24149 each time they connect. In this situation the use of the IP address as part of
24150 the retry key leads to undesirable behaviour. Setting this option false causes
24151 Exim to use only the host name.
24152 Since it is expanded it can be made to depend on the host or domain.
24155 .option serialize_hosts smtp "host list&!!" unset
24156 .cindex "serializing connections"
24157 .cindex "host" "serializing connections"
24158 Because Exim operates in a distributed manner, if several messages for the same
24159 host arrive at around the same time, more than one simultaneous connection to
24160 the remote host can occur. This is not usually a problem except when there is a
24161 slow link between the hosts. In that situation it may be helpful to restrict
24162 Exim to one connection at a time. This can be done by setting
24163 &%serialize_hosts%& to match the relevant hosts.
24165 .cindex "hints database" "serializing deliveries to a host"
24166 Exim implements serialization by means of a hints database in which a record is
24167 written whenever a process connects to one of the restricted hosts. The record
24168 is deleted when the connection is completed. Obviously there is scope for
24169 records to get left lying around if there is a system or program crash. To
24170 guard against this, Exim ignores any records that are more than six hours old.
24172 If you set up this kind of serialization, you should also arrange to delete the
24173 relevant hints database whenever your system reboots. The names of the files
24174 start with &_misc_& and they are kept in the &_spool/db_& directory. There
24175 may be one or two files, depending on the type of DBM in use. The same files
24176 are used for ETRN serialization.
24178 See also the &%max_parallel%& generic transport option.
24181 .option size_addition smtp integer 1024
24182 .cindex "SMTP" "SIZE"
24183 .cindex "message" "size issue for transport filter"
24184 .cindex "size" "of message"
24185 .cindex "transport" "filter"
24186 .cindex "filter" "transport filter"
24187 If a remote SMTP server indicates that it supports the SIZE option of the
24188 MAIL command, Exim uses this to pass over the message size at the start of
24189 an SMTP transaction. It adds the value of &%size_addition%& to the value it
24190 sends, to allow for headers and other text that may be added during delivery by
24191 configuration options or in a transport filter. It may be necessary to increase
24192 this if a lot of text is added to messages.
24194 Alternatively, if the value of &%size_addition%& is set negative, it disables
24195 the use of the SIZE option altogether.
24198 .option socks_proxy smtp string&!! unset
24199 .cindex proxy SOCKS
24200 This option enables use of SOCKS proxies for connections made by the
24201 transport. For details see section &<<SECTproxySOCKS>>&.
24204 .option tls_certificate smtp string&!! unset
24205 .cindex "TLS" "client certificate, location of"
24206 .cindex "certificate" "client, location of"
24208 .vindex "&$host_address$&"
24209 The value of this option must be the absolute path to a file which contains the
24210 client's certificate, for possible use when sending a message over an encrypted
24211 connection. The values of &$host$& and &$host_address$& are set to the name and
24212 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
24215 &*Note*&: This option must be set if you want Exim to be able to use a TLS
24216 certificate when sending messages as a client. The global option of the same
24217 name specifies the certificate for Exim as a server; it is not automatically
24218 assumed that the same certificate should be used when Exim is operating as a
24222 .option tls_crl smtp string&!! unset
24223 .cindex "TLS" "client certificate revocation list"
24224 .cindex "certificate" "revocation list for client"
24225 This option specifies a certificate revocation list. The expanded value must
24226 be the name of a file that contains a CRL in PEM format.
24229 .option tls_dh_min_bits smtp integer 1024
24230 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
24231 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
24232 key agreement is negotiated, the server will provide a large prime number
24233 for use. This option establishes the minimum acceptable size of that number.
24234 If the parameter offered by the server is too small, then the TLS handshake
24237 Only supported when using GnuTLS.
24240 .option tls_privatekey smtp string&!! unset
24241 .cindex "TLS" "client private key, location of"
24243 .vindex "&$host_address$&"
24244 The value of this option must be the absolute path to a file which contains the
24245 client's private key. This is used when sending a message over an encrypted
24246 connection using a client certificate. The values of &$host$& and
24247 &$host_address$& are set to the name and address of the server during the
24248 expansion. If this option is unset, or the expansion is forced to fail, or the
24249 result is an empty string, the private key is assumed to be in the same file as
24250 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24253 .option tls_require_ciphers smtp string&!! unset
24254 .cindex "TLS" "requiring specific ciphers"
24255 .cindex "cipher" "requiring specific"
24257 .vindex "&$host_address$&"
24258 The value of this option must be a list of permitted cipher suites, for use
24259 when setting up an outgoing encrypted connection. (There is a global option of
24260 the same name for controlling incoming connections.) The values of &$host$& and
24261 &$host_address$& are set to the name and address of the server during the
24262 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24263 is used in different ways by OpenSSL and GnuTLS (see sections
24264 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24265 ciphers is a preference order.
24269 .option tls_sni smtp string&!! unset
24270 .cindex "TLS" "Server Name Indication"
24271 .vindex "&$tls_sni$&"
24272 If this option is set then it sets the $tls_out_sni variable and causes any
24273 TLS session to pass this value as the Server Name Indication extension to
24274 the remote side, which can be used by the remote side to select an appropriate
24275 certificate and private key for the session.
24277 See &<<SECTtlssni>>& for more information.
24279 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24285 .option tls_tempfail_tryclear smtp boolean true
24286 .cindex "4&'xx'& responses" "to STARTTLS"
24287 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24288 setting up a TLS session, this option determines whether or not Exim should try
24289 to deliver the message unencrypted. If it is set false, delivery to the
24290 current host is deferred; if there are other hosts, they are tried. If this
24291 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24292 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24293 TLS negotiation fails, Exim closes the current connection (because it is in an
24294 unknown state), opens a new one to the same host, and then tries the delivery
24298 .option tls_try_verify_hosts smtp "host list&!!" *
24299 .cindex "TLS" "server certificate verification"
24300 .cindex "certificate" "verification of server"
24301 This option gives a list of hosts for which, on encrypted connections,
24302 certificate verification will be tried but need not succeed.
24303 The &%tls_verify_certificates%& option must also be set.
24304 Note that unless the host is in this list
24305 TLS connections will be denied to hosts using self-signed certificates
24306 when &%tls_verify_certificates%& is matched.
24307 The &$tls_out_certificate_verified$& variable is set when
24308 certificate verification succeeds.
24311 .option tls_verify_cert_hostnames smtp "host list&!!" *
24312 .cindex "TLS" "server certificate hostname verification"
24313 .cindex "certificate" "verification of server"
24314 This option give a list of hosts for which,
24315 while verifying the server certificate,
24316 checks will be included on the host name
24317 (note that this will generally be the result of a DNS MX lookup)
24318 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24319 limited to being the initial component of a 3-or-more component FQDN.
24321 There is no equivalent checking on client certificates.
24324 .option tls_verify_certificates smtp string&!! system
24325 .cindex "TLS" "server certificate verification"
24326 .cindex "certificate" "verification of server"
24328 .vindex "&$host_address$&"
24329 The value of this option must be either the
24331 or the absolute path to
24332 a file or directory containing permitted certificates for servers,
24333 for use when setting up an encrypted connection.
24335 The "system" value for the option will use a location compiled into the SSL library.
24336 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24337 is taken as empty and an explicit location
24340 The use of a directory for the option value is not available for GnuTLS versions
24341 preceding 3.3.6 and a single file must be used.
24343 With OpenSSL the certificates specified
24345 either by file or directory
24346 are added to those given by the system default location.
24348 The values of &$host$& and
24349 &$host_address$& are set to the name and address of the server during the
24350 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24352 For back-compatibility,
24353 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24354 (a single-colon empty list counts as being set)
24355 and certificate verification fails the TLS connection is closed.
24358 .option tls_verify_hosts smtp "host list&!!" unset
24359 .cindex "TLS" "server certificate verification"
24360 .cindex "certificate" "verification of server"
24361 This option gives a list of hosts for which, on encrypted connections,
24362 certificate verification must succeed.
24363 The &%tls_verify_certificates%& option must also be set.
24364 If both this option and &%tls_try_verify_hosts%& are unset
24365 operation is as if this option selected all hosts.
24370 .section "How the limits for the number of hosts to try are used" &&&
24372 .cindex "host" "maximum number to try"
24373 .cindex "limit" "hosts; maximum number tried"
24374 There are two options that are concerned with the number of hosts that are
24375 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
24376 &%hosts_max_try_hardlimit%&.
24379 The &%hosts_max_try%& option limits the number of hosts that are tried
24380 for a single delivery. However, despite the term &"host"& in its name, the
24381 option actually applies to each IP address independently. In other words, a
24382 multihomed host is treated as several independent hosts, just as it is for
24385 Many of the larger ISPs have multiple MX records which often point to
24386 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24387 created as a result of routing one of these domains.
24389 Trying every single IP address on such a long list does not seem sensible; if
24390 several at the top of the list fail, it is reasonable to assume there is some
24391 problem that is likely to affect all of them. Roughly speaking, the value of
24392 &%hosts_max_try%& is the maximum number that are tried before deferring the
24393 delivery. However, the logic cannot be quite that simple.
24395 Firstly, IP addresses that are skipped because their retry times have not
24396 arrived do not count, and in addition, addresses that are past their retry
24397 limits are also not counted, even when they are tried. This means that when
24398 some IP addresses are past their retry limits, more than the value of
24399 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
24400 that all IP addresses are considered before timing out an email address (but
24401 see below for an exception).
24403 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
24404 list to see if there is a subsequent host with a different (higher valued) MX.
24405 If there is, that host is considered next, and the current IP address is used
24406 but not counted. This behaviour helps in the case of a domain with a retry rule
24407 that hardly ever delays any hosts, as is now explained:
24409 Consider the case of a long list of hosts with one MX value, and a few with a
24410 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
24411 hosts at the top of the list are tried at first. With the default retry rule,
24412 which specifies increasing retry times, the higher MX hosts are eventually
24413 tried when those at the top of the list are skipped because they have not
24414 reached their retry times.
24416 However, it is common practice to put a fixed short retry time on domains for
24417 large ISPs, on the grounds that their servers are rarely down for very long.
24418 Unfortunately, these are exactly the domains that tend to resolve to long lists
24419 of hosts. The short retry time means that the lowest MX hosts are tried every
24420 time. The attempts may be in a different order because of random sorting, but
24421 without the special MX check, the higher MX hosts would never be tried until
24422 all the lower MX hosts had timed out (which might be several days), because
24423 there are always some lower MX hosts that have reached their retry times. With
24424 the special check, Exim considers at least one IP address from each MX value at
24425 every delivery attempt, even if the &%hosts_max_try%& limit has already been
24428 The above logic means that &%hosts_max_try%& is not a hard limit, and in
24429 particular, Exim normally eventually tries all the IP addresses before timing
24430 out an email address. When &%hosts_max_try%& was implemented, this seemed a
24431 reasonable thing to do. Recently, however, some lunatic DNS configurations have
24432 been set up with hundreds of IP addresses for some domains. It can
24433 take a very long time indeed for an address to time out in these cases.
24435 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
24436 Exim never tries more than this number of IP addresses; if it hits this limit
24437 and they are all timed out, the email address is bounced, even though not all
24438 possible IP addresses have been tried.
24439 .ecindex IIDsmttra1
24440 .ecindex IIDsmttra2
24446 . ////////////////////////////////////////////////////////////////////////////
24447 . ////////////////////////////////////////////////////////////////////////////
24449 .chapter "Address rewriting" "CHAPrewrite"
24450 .scindex IIDaddrew "rewriting" "addresses"
24451 There are some circumstances in which Exim automatically rewrites domains in
24452 addresses. The two most common are when an address is given without a domain
24453 (referred to as an &"unqualified address"&) or when an address contains an
24454 abbreviated domain that is expanded by DNS lookup.
24456 Unqualified envelope addresses are accepted only for locally submitted
24457 messages, or for messages that are received from hosts matching
24458 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24459 appropriate. Unqualified addresses in header lines are qualified if they are in
24460 locally submitted messages, or messages from hosts that are permitted to send
24461 unqualified envelope addresses. Otherwise, unqualified addresses in header
24462 lines are neither qualified nor rewritten.
24464 One situation in which Exim does &'not'& automatically rewrite a domain is
24465 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24466 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24467 do this. The new RFCs do not contain this suggestion.
24470 .section "Explicitly configured address rewriting" "SECID147"
24471 This chapter describes the rewriting rules that can be used in the
24472 main rewrite section of the configuration file, and also in the generic
24473 &%headers_rewrite%& option that can be set on any transport.
24475 Some people believe that configured address rewriting is a Mortal Sin.
24476 Others believe that life is not possible without it. Exim provides the
24477 facility; you do not have to use it.
24479 The main rewriting rules that appear in the &"rewrite"& section of the
24480 configuration file are applied to addresses in incoming messages, both envelope
24481 addresses and addresses in header lines. Each rule specifies the types of
24482 address to which it applies.
24484 Whether or not addresses in header lines are rewritten depends on the origin of
24485 the headers and the type of rewriting. Global rewriting, that is, rewriting
24486 rules from the rewrite section of the configuration file, is applied only to
24487 those headers that were received with the message. Header lines that are added
24488 by ACLs or by a system filter or by individual routers or transports (which
24489 are specific to individual recipient addresses) are not rewritten by the global
24492 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24493 applies all headers except those added by routers and transports. That is, as
24494 well as the headers that were received with the message, it also applies to
24495 headers that were added by an ACL or a system filter.
24498 In general, rewriting addresses from your own system or domain has some
24499 legitimacy. Rewriting other addresses should be done only with great care and
24500 in special circumstances. The author of Exim believes that rewriting should be
24501 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24502 Although it can sometimes be used as a routing tool, this is very strongly
24505 There are two commonly encountered circumstances where rewriting is used, as
24506 illustrated by these examples:
24509 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24510 exchange mail with each other behind a firewall, but there is only a single
24511 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24512 &'hitch.fict.example'& when sending mail off-site.
24514 A host rewrites the local parts of its own users so that, for example,
24515 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24520 .section "When does rewriting happen?" "SECID148"
24521 .cindex "rewriting" "timing of"
24522 .cindex "&ACL;" "rewriting addresses in"
24523 Configured address rewriting can take place at several different stages of a
24524 message's processing.
24526 .vindex "&$sender_address$&"
24527 At the start of an ACL for MAIL, the sender address may have been rewritten
24528 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24529 ordinary rewrite rules have yet been applied. If, however, the sender address
24530 is verified in the ACL, it is rewritten before verification, and remains
24531 rewritten thereafter. The subsequent value of &$sender_address$& is the
24532 rewritten address. This also applies if sender verification happens in a
24533 RCPT ACL. Otherwise, when the sender address is not verified, it is
24534 rewritten as soon as a message's header lines have been received.
24536 .vindex "&$domain$&"
24537 .vindex "&$local_part$&"
24538 Similarly, at the start of an ACL for RCPT, the current recipient's address
24539 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24540 rewrite rules have yet been applied to it. However, the behaviour is different
24541 from the sender address when a recipient is verified. The address is rewritten
24542 for the verification, but the rewriting is not remembered at this stage. The
24543 value of &$local_part$& and &$domain$& after verification are always the same
24544 as they were before (that is, they contain the unrewritten &-- except for
24545 SMTP-time rewriting &-- address).
24547 As soon as a message's header lines have been received, all the envelope
24548 recipient addresses are permanently rewritten, and rewriting is also applied to
24549 the addresses in the header lines (if configured). This happens before adding
24550 any header lines that were specified in MAIL or RCPT ACLs, and
24551 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24552 before the DATA ACL and &[local_scan()]& functions are run.
24554 When an address is being routed, either for delivery or for verification,
24555 rewriting is applied immediately to child addresses that are generated by
24556 redirection, unless &%no_rewrite%& is set on the router.
24558 .cindex "envelope sender" "rewriting at transport time"
24559 .cindex "rewriting" "at transport time"
24560 .cindex "header lines" "rewriting at transport time"
24561 At transport time, additional rewriting of addresses in header lines can be
24562 specified by setting the generic &%headers_rewrite%& option on a transport.
24563 This option contains rules that are identical in form to those in the rewrite
24564 section of the configuration file. They are applied to the original message
24565 header lines and any that were added by ACLs or a system filter. They are not
24566 applied to header lines that are added by routers or the transport.
24568 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24569 transport option. However, it is not possible to rewrite envelope recipients at
24575 .section "Testing the rewriting rules that apply on input" "SECID149"
24576 .cindex "rewriting" "testing"
24577 .cindex "testing" "rewriting"
24578 Exim's input rewriting configuration appears in a part of the run time
24579 configuration file headed by &"begin rewrite"&. It can be tested by the
24580 &%-brw%& command line option. This takes an address (which can be a full RFC
24581 2822 address) as its argument. The output is a list of how the address would be
24582 transformed by the rewriting rules for each of the different places it might
24583 appear in an incoming message, that is, for each different header and for the
24584 envelope sender and recipient fields. For example,
24586 exim -brw ph10@exim.workshop.example
24588 might produce the output
24590 sender: Philip.Hazel@exim.workshop.example
24591 from: Philip.Hazel@exim.workshop.example
24592 to: ph10@exim.workshop.example
24593 cc: ph10@exim.workshop.example
24594 bcc: ph10@exim.workshop.example
24595 reply-to: Philip.Hazel@exim.workshop.example
24596 env-from: Philip.Hazel@exim.workshop.example
24597 env-to: ph10@exim.workshop.example
24599 which shows that rewriting has been set up for that address when used in any of
24600 the source fields, but not when it appears as a recipient address. At the
24601 present time, there is no equivalent way of testing rewriting rules that are
24602 set for a particular transport.
24605 .section "Rewriting rules" "SECID150"
24606 .cindex "rewriting" "rules"
24607 The rewrite section of the configuration file consists of lines of rewriting
24610 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24612 Rewriting rules that are specified for the &%headers_rewrite%& generic
24613 transport option are given as a colon-separated list. Each item in the list
24614 takes the same form as a line in the main rewriting configuration (except that
24615 any colons must be doubled, of course).
24617 The formats of source patterns and replacement strings are described below.
24618 Each is terminated by white space, unless enclosed in double quotes, in which
24619 case normal quoting conventions apply inside the quotes. The flags are single
24620 characters which may appear in any order. Spaces and tabs between them are
24623 For each address that could potentially be rewritten, the rules are scanned in
24624 order, and replacements for the address from earlier rules can themselves be
24625 replaced by later rules (but see the &"q"& and &"R"& flags).
24627 The order in which addresses are rewritten is undefined, may change between
24628 releases, and must not be relied on, with one exception: when a message is
24629 received, the envelope sender is always rewritten first, before any header
24630 lines are rewritten. For example, the replacement string for a rewrite of an
24631 address in &'To:'& must not assume that the message's address in &'From:'& has
24632 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24633 that the envelope sender has already been rewritten.
24635 .vindex "&$domain$&"
24636 .vindex "&$local_part$&"
24637 The variables &$local_part$& and &$domain$& can be used in the replacement
24638 string to refer to the address that is being rewritten. Note that lookup-driven
24639 rewriting can be done by a rule of the form
24643 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24644 refer to the address that is being rewritten.
24647 .section "Rewriting patterns" "SECID151"
24648 .cindex "rewriting" "patterns"
24649 .cindex "address list" "in a rewriting pattern"
24650 The source pattern in a rewriting rule is any item which may appear in an
24651 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24652 single-item address list, which means that it is expanded before being tested
24653 against the address. As always, if you use a regular expression as a pattern,
24654 you must take care to escape dollar and backslash characters, or use the &`\N`&
24655 facility to suppress string expansion within the regular expression.
24657 Domains in patterns should be given in lower case. Local parts in patterns are
24658 case-sensitive. If you want to do case-insensitive matching of local parts, you
24659 can use a regular expression that starts with &`^(?i)`&.
24661 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
24662 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
24663 depending on the type of match which occurred. These can be used in the
24664 replacement string to insert portions of the incoming address. &$0$& always
24665 refers to the complete incoming address. When a regular expression is used, the
24666 numerical variables are set from its capturing subexpressions. For other types
24667 of pattern they are set as follows:
24670 If a local part or domain starts with an asterisk, the numerical variables
24671 refer to the character strings matched by asterisks, with &$1$& associated with
24672 the first asterisk, and &$2$& with the second, if present. For example, if the
24675 *queen@*.fict.example
24677 is matched against the address &'hearts-queen@wonderland.fict.example'& then
24679 $0 = hearts-queen@wonderland.fict.example
24683 Note that if the local part does not start with an asterisk, but the domain
24684 does, it is &$1$& that contains the wild part of the domain.
24687 If the domain part of the pattern is a partial lookup, the wild and fixed parts
24688 of the domain are placed in the next available numerical variables. Suppose,
24689 for example, that the address &'foo@bar.baz.example'& is processed by a
24690 rewriting rule of the form
24692 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
24694 and the key in the file that matches the domain is &`*.baz.example`&. Then
24700 If the address &'foo@baz.example'& is looked up, this matches the same
24701 wildcard file entry, and in this case &$2$& is set to the empty string, but
24702 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
24703 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
24704 whole domain. For non-partial domain lookups, no numerical variables are set.
24708 .section "Rewriting replacements" "SECID152"
24709 .cindex "rewriting" "replacements"
24710 If the replacement string for a rule is a single asterisk, addresses that
24711 match the pattern and the flags are &'not'& rewritten, and no subsequent
24712 rewriting rules are scanned. For example,
24714 hatta@lookingglass.fict.example * f
24716 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
24719 .vindex "&$domain$&"
24720 .vindex "&$local_part$&"
24721 If the replacement string is not a single asterisk, it is expanded, and must
24722 yield a fully qualified address. Within the expansion, the variables
24723 &$local_part$& and &$domain$& refer to the address that is being rewritten.
24724 Any letters they contain retain their original case &-- they are not lower
24725 cased. The numerical variables are set up according to the type of pattern that
24726 matched the address, as described above. If the expansion is forced to fail by
24727 the presence of &"fail"& in a conditional or lookup item, rewriting by the
24728 current rule is abandoned, but subsequent rules may take effect. Any other
24729 expansion failure causes the entire rewriting operation to be abandoned, and an
24730 entry written to the panic log.
24734 .section "Rewriting flags" "SECID153"
24735 There are three different kinds of flag that may appear on rewriting rules:
24738 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
24741 A flag that specifies rewriting at SMTP time: S.
24743 Flags that control the rewriting process: Q, q, R, w.
24746 For rules that are part of the &%headers_rewrite%& generic transport option,
24747 E, F, T, and S are not permitted.
24751 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
24753 .cindex "rewriting" "flags"
24754 If none of the following flag letters, nor the &"S"& flag (see section
24755 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
24756 and to both the sender and recipient fields of the envelope, whereas a
24757 transport-time rewriting rule just applies to all headers. Otherwise, the
24758 rewriting rule is skipped unless the relevant addresses are being processed.
24760 &`E`& rewrite all envelope fields
24761 &`F`& rewrite the envelope From field
24762 &`T`& rewrite the envelope To field
24763 &`b`& rewrite the &'Bcc:'& header
24764 &`c`& rewrite the &'Cc:'& header
24765 &`f`& rewrite the &'From:'& header
24766 &`h`& rewrite all headers
24767 &`r`& rewrite the &'Reply-To:'& header
24768 &`s`& rewrite the &'Sender:'& header
24769 &`t`& rewrite the &'To:'& header
24771 "All headers" means all of the headers listed above that can be selected
24772 individually, plus their &'Resent-'& versions. It does not include
24773 other headers such as &'Subject:'& etc.
24775 You should be particularly careful about rewriting &'Sender:'& headers, and
24776 restrict this to special known cases in your own domains.
24779 .section "The SMTP-time rewriting flag" "SECTrewriteS"
24780 .cindex "SMTP" "rewriting malformed addresses"
24781 .cindex "RCPT" "rewriting argument of"
24782 .cindex "MAIL" "rewriting argument of"
24783 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
24784 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
24785 before any other processing; even before syntax checking. The pattern is
24786 required to be a regular expression, and it is matched against the whole of the
24787 data for the command, including any surrounding angle brackets.
24789 .vindex "&$domain$&"
24790 .vindex "&$local_part$&"
24791 This form of rewrite rule allows for the handling of addresses that are not
24792 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
24793 input). Because the input is not required to be a syntactically valid address,
24794 the variables &$local_part$& and &$domain$& are not available during the
24795 expansion of the replacement string. The result of rewriting replaces the
24796 original address in the MAIL or RCPT command.
24799 .section "Flags controlling the rewriting process" "SECID155"
24800 There are four flags which control the way the rewriting process works. These
24801 take effect only when a rule is invoked, that is, when the address is of the
24802 correct type (matches the flags) and matches the pattern:
24805 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
24806 unqualified local part. It is qualified with &%qualify_recipient%&. In the
24807 absence of &"Q"& the rewritten address must always include a domain.
24809 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
24810 even if no rewriting actually takes place because of a &"fail"& in the
24811 expansion. The &"q"& flag is not effective if the address is of the wrong type
24812 (does not match the flags) or does not match the pattern.
24814 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
24815 address, up to ten times. It can be combined with the &"q"& flag, to stop
24816 rewriting once it fails to match (after at least one successful rewrite).
24818 .cindex "rewriting" "whole addresses"
24819 When an address in a header is rewritten, the rewriting normally applies only
24820 to the working part of the address, with any comments and RFC 2822 &"phrase"&
24821 left unchanged. For example, rewriting might change
24823 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
24827 From: Ford Prefect <prefectf@hitch.fict.example>
24830 Sometimes there is a need to replace the whole address item, and this can be
24831 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
24832 causes an address in a header line to be rewritten, the entire address is
24833 replaced, not just the working part. The replacement must be a complete RFC
24834 2822 address, including the angle brackets if necessary. If text outside angle
24835 brackets contains a character whose value is greater than 126 or less than 32
24836 (except for tab), the text is encoded according to RFC 2047. The character set
24837 is taken from &%headers_charset%&, which gets its default at build time.
24839 When the &"w"& flag is set on a rule that causes an envelope address to be
24840 rewritten, all but the working part of the replacement address is discarded.
24844 .section "Rewriting examples" "SECID156"
24845 Here is an example of the two common rewriting paradigms:
24847 *@*.hitch.fict.example $1@hitch.fict.example
24848 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
24849 {$value}fail}@hitch.fict.example bctfrF
24851 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
24852 the string expansion to fail if the lookup does not succeed. In this context it
24853 has the effect of leaving the original address unchanged, but Exim goes on to
24854 consider subsequent rewriting rules, if any, because the &"q"& flag is not
24855 present in that rule. An alternative to &"fail"& would be to supply &$1$&
24856 explicitly, which would cause the rewritten address to be the same as before,
24857 at the cost of a small bit of processing. Not supplying either of these is an
24858 error, since the rewritten address would then contain no local part.
24860 The first example above replaces the domain with a superior, more general
24861 domain. This may not be desirable for certain local parts. If the rule
24863 root@*.hitch.fict.example *
24865 were inserted before the first rule, rewriting would be suppressed for the
24866 local part &'root'& at any domain ending in &'hitch.fict.example'&.
24868 Rewriting can be made conditional on a number of tests, by making use of
24869 &${if$& in the expansion item. For example, to apply a rewriting rule only to
24870 messages that originate outside the local host:
24872 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
24873 {$1@hitch.fict.example}fail}"
24875 The replacement string is quoted in this example because it contains white
24878 .cindex "rewriting" "bang paths"
24879 .cindex "bang paths" "rewriting"
24880 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
24881 an address it treats it as an unqualified local part which it qualifies with
24882 the local qualification domain (if the source of the message is local or if the
24883 remote host is permitted to send unqualified addresses). Rewriting can
24884 sometimes be used to handle simple bang paths with a fixed number of
24885 components. For example, the rule
24887 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
24889 rewrites a two-component bang path &'host.name!user'& as the domain address
24890 &'user@host.name'&. However, there is a security implication in using this as
24891 a global rewriting rule for envelope addresses. It can provide a backdoor
24892 method for using your system as a relay, because the incoming addresses appear
24893 to be local. If the bang path addresses are received via SMTP, it is safer to
24894 use the &"S"& flag to rewrite them as they are received, so that relay checking
24895 can be done on the rewritten addresses.
24902 . ////////////////////////////////////////////////////////////////////////////
24903 . ////////////////////////////////////////////////////////////////////////////
24905 .chapter "Retry configuration" "CHAPretry"
24906 .scindex IIDretconf1 "retry" "configuration, description of"
24907 .scindex IIDregconf2 "configuration file" "retry section"
24908 The &"retry"& section of the runtime configuration file contains a list of
24909 retry rules that control how often Exim tries to deliver messages that cannot
24910 be delivered at the first attempt. If there are no retry rules (the section is
24911 empty or not present), there are no retries. In this situation, temporary
24912 errors are treated as permanent. The default configuration contains a single,
24913 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
24914 line option can be used to test which retry rule will be used for a given
24915 address, domain and error.
24917 The most common cause of retries is temporary failure to deliver to a remote
24918 host because the host is down, or inaccessible because of a network problem.
24919 Exim's retry processing in this case is applied on a per-host (strictly, per IP
24920 address) basis, not on a per-message basis. Thus, if one message has recently
24921 been delayed, delivery of a new message to the same host is not immediately
24922 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
24923 log selector is set, the message
24924 .cindex "retry" "time not reached"
24925 &"retry time not reached"& is written to the main log whenever a delivery is
24926 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
24927 the handling of errors during remote deliveries.
24929 Retry processing applies to routing as well as to delivering, except as covered
24930 in the next paragraph. The retry rules do not distinguish between these
24931 actions. It is not possible, for example, to specify different behaviour for
24932 failures to route the domain &'snark.fict.example'& and failures to deliver to
24933 the host &'snark.fict.example'&. I didn't think anyone would ever need this
24934 added complication, so did not implement it. However, although they share the
24935 same retry rule, the actual retry times for routing and transporting a given
24936 domain are maintained independently.
24938 When a delivery is not part of a queue run (typically an immediate delivery on
24939 receipt of a message), the routers are always run, and local deliveries are
24940 always attempted, even if retry times are set for them. This makes for better
24941 behaviour if one particular message is causing problems (for example, causing
24942 quota overflow, or provoking an error in a filter file). If such a delivery
24943 suffers a temporary failure, the retry data is updated as normal, and
24944 subsequent delivery attempts from queue runs occur only when the retry time for
24945 the local address is reached.
24947 .section "Changing retry rules" "SECID157"
24948 If you change the retry rules in your configuration, you should consider
24949 whether or not to delete the retry data that is stored in Exim's spool area in
24950 files with names like &_db/retry_&. Deleting any of Exim's hints files is
24951 always safe; that is why they are called &"hints"&.
24953 The hints retry data contains suggested retry times based on the previous
24954 rules. In the case of a long-running problem with a remote host, it might
24955 record the fact that the host has timed out. If your new rules increase the
24956 timeout time for such a host, you should definitely remove the old retry data
24957 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
24958 messages that it should now be retaining.
24962 .section "Format of retry rules" "SECID158"
24963 .cindex "retry" "rules"
24964 Each retry rule occupies one line and consists of three or four parts,
24965 separated by white space: a pattern, an error name, an optional list of sender
24966 addresses, and a list of retry parameters. The pattern and sender lists must be
24967 enclosed in double quotes if they contain white space. The rules are searched
24968 in order until one is found where the pattern, error name, and sender list (if
24969 present) match the failing host or address, the error that occurred, and the
24970 message's sender, respectively.
24973 The pattern is any single item that may appear in an address list (see section
24974 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
24975 which means that it is expanded before being tested against the address that
24976 has been delayed. A negated address list item is permitted. Address
24977 list processing treats a plain domain name as if it were preceded by &"*@"&,
24978 which makes it possible for many retry rules to start with just a domain. For
24981 lookingglass.fict.example * F,24h,30m;
24983 provides a rule for any address in the &'lookingglass.fict.example'& domain,
24986 alice@lookingglass.fict.example * F,24h,30m;
24988 applies only to temporary failures involving the local part &%alice%&.
24989 In practice, almost all rules start with a domain name pattern without a local
24992 .cindex "regular expressions" "in retry rules"
24993 &*Warning*&: If you use a regular expression in a retry rule pattern, it
24994 must match a complete address, not just a domain, because that is how regular
24995 expressions work in address lists.
24997 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
24998 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
25002 .section "Choosing which retry rule to use for address errors" "SECID159"
25003 When Exim is looking for a retry rule after a routing attempt has failed (for
25004 example, after a DNS timeout), each line in the retry configuration is tested
25005 against the complete address only if &%retry_use_local_part%& is set for the
25006 router. Otherwise, only the domain is used, except when matching against a
25007 regular expression, when the local part of the address is replaced with &"*"&.
25008 A domain on its own can match a domain pattern, or a pattern that starts with
25009 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
25010 &%check_local_user%& is true, and false for other routers.
25012 Similarly, when Exim is looking for a retry rule after a local delivery has
25013 failed (for example, after a mailbox full error), each line in the retry
25014 configuration is tested against the complete address only if
25015 &%retry_use_local_part%& is set for the transport (it defaults true for all
25018 .cindex "4&'xx'& responses" "retry rules for"
25019 However, when Exim is looking for a retry rule after a remote delivery attempt
25020 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
25021 whole address is always used as the key when searching the retry rules. The
25022 rule that is found is used to create a retry time for the combination of the
25023 failing address and the message's sender. It is the combination of sender and
25024 recipient that is delayed in subsequent queue runs until its retry time is
25025 reached. You can delay the recipient without regard to the sender by setting
25026 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
25027 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
25032 .section "Choosing which retry rule to use for host and message errors" &&&
25034 For a temporary error that is not related to an individual address (for
25035 example, a connection timeout), each line in the retry configuration is checked
25036 twice. First, the name of the remote host is used as a domain name (preceded by
25037 &"*@"& when matching a regular expression). If this does not match the line,
25038 the domain from the email address is tried in a similar fashion. For example,
25039 suppose the MX records for &'a.b.c.example'& are
25041 a.b.c.example MX 5 x.y.z.example
25045 and the retry rules are
25047 p.q.r.example * F,24h,30m;
25048 a.b.c.example * F,4d,45m;
25050 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
25051 first rule matches neither the host nor the domain, so Exim looks at the second
25052 rule. This does not match the host, but it does match the domain, so it is used
25053 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
25054 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
25055 first retry rule is used, because it matches the host.
25057 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
25058 first rule to determine retry times, but for all the other hosts for the domain
25059 &'a.b.c.example'&, the second rule is used. The second rule is also used if
25060 routing to &'a.b.c.example'& suffers a temporary failure.
25062 &*Note*&: The host name is used when matching the patterns, not its IP address.
25063 However, if a message is routed directly to an IP address without the use of a
25064 host name, for example, if a &(manualroute)& router contains a setting such as:
25066 route_list = *.a.example 192.168.34.23
25068 then the &"host name"& that is used when searching for a retry rule is the
25069 textual form of the IP address.
25071 .section "Retry rules for specific errors" "SECID161"
25072 .cindex "retry" "specific errors; specifying"
25073 The second field in a retry rule is the name of a particular error, or an
25074 asterisk, which matches any error. The errors that can be tested for are:
25077 .vitem &%auth_failed%&
25078 Authentication failed when trying to send to a host in the
25079 &%hosts_require_auth%& list in an &(smtp)& transport.
25081 .vitem &%data_4xx%&
25082 A 4&'xx'& error was received for an outgoing DATA command, either immediately
25083 after the command, or after sending the message's data.
25085 .vitem &%mail_4xx%&
25086 A 4&'xx'& error was received for an outgoing MAIL command.
25088 .vitem &%rcpt_4xx%&
25089 A 4&'xx'& error was received for an outgoing RCPT command.
25092 For the three 4&'xx'& errors, either the first or both of the x's can be given
25093 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
25094 recognize 452 errors given to RCPT commands for addresses in a certain domain,
25095 and have retries every ten minutes with a one-hour timeout, you could set up a
25096 retry rule of this form:
25098 the.domain.name rcpt_452 F,1h,10m
25100 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
25101 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
25104 .vitem &%lost_connection%&
25105 A server unexpectedly closed the SMTP connection. There may, of course,
25106 legitimate reasons for this (host died, network died), but if it repeats a lot
25107 for the same host, it indicates something odd.
25110 A DNS lookup for a host failed.
25111 Note that a &%dnslookup%& router will need to have matched
25112 its &%fail_defer_domains%& option for this retry type to be usable.
25113 Also note that a &%manualroute%& router will probably need
25114 its &%host_find_failed%& option set to &%defer%&.
25116 .vitem &%refused_MX%&
25117 A connection to a host obtained from an MX record was refused.
25119 .vitem &%refused_A%&
25120 A connection to a host not obtained from an MX record was refused.
25123 A connection was refused.
25125 .vitem &%timeout_connect_MX%&
25126 A connection attempt to a host obtained from an MX record timed out.
25128 .vitem &%timeout_connect_A%&
25129 A connection attempt to a host not obtained from an MX record timed out.
25131 .vitem &%timeout_connect%&
25132 A connection attempt timed out.
25134 .vitem &%timeout_MX%&
25135 There was a timeout while connecting or during an SMTP session with a host
25136 obtained from an MX record.
25138 .vitem &%timeout_A%&
25139 There was a timeout while connecting or during an SMTP session with a host not
25140 obtained from an MX record.
25143 There was a timeout while connecting or during an SMTP session.
25145 .vitem &%tls_required%&
25146 The server was required to use TLS (it matched &%hosts_require_tls%& in the
25147 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
25148 to STARTTLS, or there was a problem setting up the TLS connection.
25151 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25154 .vitem &%quota_%&<&'time'&>
25155 .cindex "quota" "error testing in retry rule"
25156 .cindex "retry" "quota error testing"
25157 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25158 transport, and the mailbox has not been accessed for <&'time'&>. For example,
25159 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
25163 .cindex "mailbox" "time of last read"
25164 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
25165 timeouts when the mailbox is full and is not being read by its owner. Ideally,
25166 it should be based on the last time that the user accessed the mailbox.
25167 However, it is not always possible to determine this. Exim uses the following
25171 If the mailbox is a single file, the time of last access (the &"atime"&) is
25172 used. As no new messages are being delivered (because the mailbox is over
25173 quota), Exim does not access the file, so this is the time of last user access.
25175 .cindex "maildir format" "time of last read"
25176 For a maildir delivery, the time of last modification of the &_new_&
25177 subdirectory is used. As the mailbox is over quota, no new files are created in
25178 the &_new_& subdirectory, because no new messages are being delivered. Any
25179 change to the &_new_& subdirectory is therefore assumed to be the result of an
25180 MUA moving a new message to the &_cur_& directory when it is first read. The
25181 time that is used is therefore the last time that the user read a new message.
25183 For other kinds of multi-file mailbox, the time of last access cannot be
25184 obtained, so a retry rule that uses this type of error field is never matched.
25187 The quota errors apply both to system-enforced quotas and to Exim's own quota
25188 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
25189 when a local delivery is deferred because a partition is full (the ENOSPC
25194 .section "Retry rules for specified senders" "SECID162"
25195 .cindex "retry" "rules; sender-specific"
25196 You can specify retry rules that apply only when the failing message has a
25197 specific sender. In particular, this can be used to define retry rules that
25198 apply only to bounce messages. The third item in a retry rule can be of this
25201 &`senders=`&<&'address list'&>
25203 The retry timings themselves are then the fourth item. For example:
25205 * rcpt_4xx senders=: F,1h,30m
25207 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
25208 host. If the address list contains white space, it must be enclosed in quotes.
25211 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
25213 &*Warning*&: This facility can be unhelpful if it is used for host errors
25214 (which do not depend on the recipient). The reason is that the sender is used
25215 only to match the retry rule. Once the rule has been found for a host error,
25216 its contents are used to set a retry time for the host, and this will apply to
25217 all messages, not just those with specific senders.
25219 When testing retry rules using &%-brt%&, you can supply a sender using the
25220 &%-f%& command line option, like this:
25222 exim -f "" -brt user@dom.ain
25224 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
25225 list is never matched.
25231 .section "Retry parameters" "SECID163"
25232 .cindex "retry" "parameters in rules"
25233 The third (or fourth, if a senders list is present) field in a retry rule is a
25234 sequence of retry parameter sets, separated by semicolons. Each set consists of
25236 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
25238 The letter identifies the algorithm for computing a new retry time; the cutoff
25239 time is the time beyond which this algorithm no longer applies, and the
25240 arguments vary the algorithm's action. The cutoff time is measured from the
25241 time that the first failure for the domain (combined with the local part if
25242 relevant) was detected, not from the time the message was received.
25244 .cindex "retry" "algorithms"
25245 .cindex "retry" "fixed intervals"
25246 .cindex "retry" "increasing intervals"
25247 .cindex "retry" "random intervals"
25248 The available algorithms are:
25251 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25254 &'G'&: retry at geometrically increasing intervals. The first argument
25255 specifies a starting value for the interval, and the second a multiplier, which
25256 is used to increase the size of the interval at each retry.
25258 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25259 retry, the previous interval is multiplied by the factor in order to get a
25260 maximum for the next interval. The minimum interval is the first argument of
25261 the parameter, and an actual interval is chosen randomly between them. Such a
25262 rule has been found to be helpful in cluster configurations when all the
25263 members of the cluster restart at once, and may therefore synchronize their
25264 queue processing times.
25267 When computing the next retry time, the algorithm definitions are scanned in
25268 order until one whose cutoff time has not yet passed is reached. This is then
25269 used to compute a new retry time that is later than the current time. In the
25270 case of fixed interval retries, this simply means adding the interval to the
25271 current time. For geometrically increasing intervals, retry intervals are
25272 computed from the rule's parameters until one that is greater than the previous
25273 interval is found. The main configuration variable
25274 .cindex "limit" "retry interval"
25275 .cindex "retry" "interval, maximum"
25276 .oindex "&%retry_interval_max%&"
25277 &%retry_interval_max%& limits the maximum interval between retries. It
25278 cannot be set greater than &`24h`&, which is its default value.
25280 A single remote domain may have a number of hosts associated with it, and each
25281 host may have more than one IP address. Retry algorithms are selected on the
25282 basis of the domain name, but are applied to each IP address independently. If,
25283 for example, a host has two IP addresses and one is unusable, Exim will
25284 generate retry times for it and will not try to use it until its next retry
25285 time comes. Thus the good IP address is likely to be tried first most of the
25288 .cindex "hints database" "use for retrying"
25289 Retry times are hints rather than promises. Exim does not make any attempt to
25290 run deliveries exactly at the computed times. Instead, a queue runner process
25291 starts delivery processes for delayed messages periodically, and these attempt
25292 new deliveries only for those addresses that have passed their next retry time.
25293 If a new message arrives for a deferred address, an immediate delivery attempt
25294 occurs only if the address has passed its retry time. In the absence of new
25295 messages, the minimum time between retries is the interval between queue runner
25296 processes. There is not much point in setting retry times of five minutes if
25297 your queue runners happen only once an hour, unless there are a significant
25298 number of incoming messages (which might be the case on a system that is
25299 sending everything to a smart host, for example).
25301 The data in the retry hints database can be inspected by using the
25302 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25303 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25304 &'exinext'& utility script can be used to find out what the next retry times
25305 are for the hosts associated with a particular mail domain, and also for local
25306 deliveries that have been deferred.
25309 .section "Retry rule examples" "SECID164"
25310 Here are some example retry rules:
25312 alice@wonderland.fict.example quota_5d F,7d,3h
25313 wonderland.fict.example quota_5d
25314 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25315 lookingglass.fict.example * F,24h,30m;
25316 * refused_A F,2h,20m;
25317 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25319 The first rule sets up special handling for mail to
25320 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25321 mailbox has not been read for at least 5 days. Retries continue every three
25322 hours for 7 days. The second rule handles over-quota errors for all other local
25323 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25324 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25325 fail are bounced immediately if the mailbox has not been read for at least 5
25328 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25329 happen every 15 minutes for an hour, then with geometrically increasing
25330 intervals until two days have passed since a delivery first failed. After the
25331 first hour there is a delay of one hour, then two hours, then four hours, and
25332 so on (this is a rather extreme example).
25334 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25335 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25336 all other domains, with special action for connection refusal from hosts that
25337 were not obtained from an MX record.
25339 The final rule in a retry configuration should always have asterisks in the
25340 first two fields so as to provide a general catch-all for any addresses that do
25341 not have their own special handling. This example tries every 15 minutes for 2
25342 hours, then with intervals starting at one hour and increasing by a factor of
25343 1.5 up to 16 hours, then every 8 hours up to 5 days.
25347 .section "Timeout of retry data" "SECID165"
25348 .cindex "timeout" "of retry data"
25349 .oindex "&%retry_data_expire%&"
25350 .cindex "hints database" "data expiry"
25351 .cindex "retry" "timeout of data"
25352 Exim timestamps the data that it writes to its retry hints database. When it
25353 consults the data during a delivery it ignores any that is older than the value
25354 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25355 been tried for 7 days, Exim will try to deliver to it immediately a message
25356 arrives, and if that fails, it will calculate a retry time as if it were
25357 failing for the first time.
25359 This improves the behaviour for messages routed to rarely-used hosts such as MX
25360 backups. If such a host was down at one time, and happens to be down again when
25361 Exim tries a month later, using the old retry data would imply that it had been
25362 down all the time, which is not a justified assumption.
25364 If a host really is permanently dead, this behaviour causes a burst of retries
25365 every now and again, but only if messages routed to it are rare. If there is a
25366 message at least once every 7 days the retry data never expires.
25371 .section "Long-term failures" "SECID166"
25372 .cindex "delivery failure, long-term"
25373 .cindex "retry" "after long-term failure"
25374 Special processing happens when an email address has been failing for so long
25375 that the cutoff time for the last algorithm is reached. For example, using the
25376 default retry rule:
25378 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
25380 the cutoff time is four days. Reaching the retry cutoff is independent of how
25381 long any specific message has been failing; it is the length of continuous
25382 failure for the recipient address that counts.
25384 When the cutoff time is reached for a local delivery, or for all the IP
25385 addresses associated with a remote delivery, a subsequent delivery failure
25386 causes Exim to give up on the address, and a bounce message is generated.
25387 In order to cater for new messages that use the failing address, a next retry
25388 time is still computed from the final algorithm, and is used as follows:
25390 For local deliveries, one delivery attempt is always made for any subsequent
25391 messages. If this delivery fails, the address fails immediately. The
25392 post-cutoff retry time is not used.
25394 If the delivery is remote, there are two possibilities, controlled by the
25395 .oindex "&%delay_after_cutoff%&"
25396 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
25397 default. Until the post-cutoff retry time for one of the IP addresses is
25398 reached, the failing email address is bounced immediately, without a delivery
25399 attempt taking place. After that time, one new delivery attempt is made to
25400 those IP addresses that are past their retry times, and if that still fails,
25401 the address is bounced and new retry times are computed.
25403 In other words, when all the hosts for a given email address have been failing
25404 for a long time, Exim bounces rather then defers until one of the hosts' retry
25405 times is reached. Then it tries once, and bounces if that attempt fails. This
25406 behaviour ensures that few resources are wasted in repeatedly trying to deliver
25407 to a broken destination, but if the host does recover, Exim will eventually
25410 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25411 addresses are past their final cutoff time, Exim tries to deliver to those IP
25412 addresses that have not been tried since the message arrived. If there are
25413 no suitable IP addresses, or if they all fail, the address is bounced. In other
25414 words, it does not delay when a new message arrives, but tries the expired
25415 addresses immediately, unless they have been tried since the message arrived.
25416 If there is a continuous stream of messages for the failing domains, setting
25417 &%delay_after_cutoff%& false means that there will be many more attempts to
25418 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
25421 .section "Deliveries that work intermittently" "SECID167"
25422 .cindex "retry" "intermittently working deliveries"
25423 Some additional logic is needed to cope with cases where a host is
25424 intermittently available, or when a message has some attribute that prevents
25425 its delivery when others to the same address get through. In this situation,
25426 because some messages are successfully delivered, the &"retry clock"& for the
25427 host or address keeps getting reset by the successful deliveries, and so
25428 failing messages remain on the queue for ever because the cutoff time is never
25431 Two exceptional actions are applied to prevent this happening. The first
25432 applies to errors that are related to a message rather than a remote host.
25433 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
25434 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
25435 commands, and quota failures. For this type of error, if a message's arrival
25436 time is earlier than the &"first failed"& time for the error, the earlier time
25437 is used when scanning the retry rules to decide when to try next and when to
25438 time out the address.
25440 The exceptional second action applies in all cases. If a message has been on
25441 the queue for longer than the cutoff time of any applicable retry rule for a
25442 given address, a delivery is attempted for that address, even if it is not yet
25443 time, and if this delivery fails, the address is timed out. A new retry time is
25444 not computed in this case, so that other messages for the same address are
25445 considered immediately.
25446 .ecindex IIDretconf1
25447 .ecindex IIDregconf2
25454 . ////////////////////////////////////////////////////////////////////////////
25455 . ////////////////////////////////////////////////////////////////////////////
25457 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25458 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25459 .scindex IIDauthconf2 "authentication"
25460 The &"authenticators"& section of Exim's run time configuration is concerned
25461 with SMTP authentication. This facility is an extension to the SMTP protocol,
25462 described in RFC 2554, which allows a client SMTP host to authenticate itself
25463 to a server. This is a common way for a server to recognize clients that are
25464 permitted to use it as a relay. SMTP authentication is not of relevance to the
25465 transfer of mail between servers that have no managerial connection with each
25468 .cindex "AUTH" "description of"
25469 Very briefly, the way SMTP authentication works is as follows:
25472 The server advertises a number of authentication &'mechanisms'& in response to
25473 the client's EHLO command.
25475 The client issues an AUTH command, naming a specific mechanism. The command
25476 may, optionally, contain some authentication data.
25478 The server may issue one or more &'challenges'&, to which the client must send
25479 appropriate responses. In simple authentication mechanisms, the challenges are
25480 just prompts for user names and passwords. The server does not have to issue
25481 any challenges &-- in some mechanisms the relevant data may all be transmitted
25482 with the AUTH command.
25484 The server either accepts or denies authentication.
25486 If authentication succeeds, the client may optionally make use of the AUTH
25487 option on the MAIL command to pass an authenticated sender in subsequent
25488 mail transactions. Authentication lasts for the remainder of the SMTP
25491 If authentication fails, the client may give up, or it may try a different
25492 authentication mechanism, or it may try transferring mail over the
25493 unauthenticated connection.
25496 If you are setting up a client, and want to know which authentication
25497 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25498 SMTP port) on the server, and issue an EHLO command. The response to this
25499 includes the list of supported mechanisms. For example:
25501 &`$ `&&*&`telnet server.example 25`&*&
25502 &`Trying 192.168.34.25...`&
25503 &`Connected to server.example.`&
25504 &`Escape character is '^]'.`&
25505 &`220 server.example ESMTP Exim 4.20 ...`&
25506 &*&`ehlo client.example`&*&
25507 &`250-server.example Hello client.example [10.8.4.5]`&
25508 &`250-SIZE 52428800`&
25513 The second-last line of this example output shows that the server supports
25514 authentication using the PLAIN mechanism. In Exim, the different authentication
25515 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25516 routers and transports, which authenticators are included in the binary is
25517 controlled by build-time definitions. The following are currently available,
25518 included by setting
25521 AUTH_CYRUS_SASL=yes
25524 AUTH_HEIMDAL_GSSAPI=yes
25529 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25530 authentication mechanism (RFC 2195), and the second provides an interface to
25531 the Cyrus SASL authentication library.
25532 The third is an interface to Dovecot's authentication system, delegating the
25533 work via a socket interface.
25534 The fourth provides an interface to the GNU SASL authentication library, which
25535 provides mechanisms but typically not data sources.
25536 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25537 supporting setting a server keytab.
25538 The sixth can be configured to support
25539 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25540 not formally documented, but used by several MUAs. The seventh authenticator
25541 supports Microsoft's &'Secure Password Authentication'& mechanism.
25542 The eighth is an Exim authenticator but not an SMTP one;
25543 instead it can use information from a TLS negotiation.
25545 The authenticators are configured using the same syntax as other drivers (see
25546 section &<<SECTfordricon>>&). If no authenticators are required, no
25547 authentication section need be present in the configuration file. Each
25548 authenticator can in principle have both server and client functions. When Exim
25549 is receiving SMTP mail, it is acting as a server; when it is sending out
25550 messages over SMTP, it is acting as a client. Authenticator configuration
25551 options are provided for use in both these circumstances.
25553 To make it clear which options apply to which situation, the prefixes
25554 &%server_%& and &%client_%& are used on option names that are specific to
25555 either the server or the client function, respectively. Server and client
25556 functions are disabled if none of their options are set. If an authenticator is
25557 to be used for both server and client functions, a single definition, using
25558 both sets of options, is required. For example:
25562 public_name = CRAM-MD5
25563 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25565 client_secret = secret2
25567 The &%server_%& option is used when Exim is acting as a server, and the
25568 &%client_%& options when it is acting as a client.
25570 Descriptions of the individual authenticators are given in subsequent chapters.
25571 The remainder of this chapter covers the generic options for the
25572 authenticators, followed by general discussion of the way authentication works
25575 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25576 per-mechanism basis. Please read carefully to determine which variables hold
25577 account labels such as usercodes and which hold passwords or other
25578 authenticating data.
25580 Note that some mechanisms support two different identifiers for accounts: the
25581 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25582 and &'authz'& are commonly encountered. The American spelling is standard here.
25583 Conceptually, authentication data such as passwords are tied to the identifier
25584 used to authenticate; servers may have rules to permit one user to act as a
25585 second user, so that after login the session is treated as though that second
25586 user had logged in. That second user is the &'authorization id'&. A robust
25587 configuration might confirm that the &'authz'& field is empty or matches the
25588 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25589 as verified data, the &'authz'& as an unverified request which the server might
25592 A &'realm'& is a text string, typically a domain name, presented by a server
25593 to a client to help it select an account and credentials to use. In some
25594 mechanisms, the client and server provably agree on the realm, but clients
25595 typically can not treat the realm as secure data to be blindly trusted.
25599 .section "Generic options for authenticators" "SECID168"
25600 .cindex "authentication" "generic options"
25601 .cindex "options" "generic; for authenticators"
25603 .option client_condition authenticators string&!! unset
25604 When Exim is authenticating as a client, it skips any authenticator whose
25605 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25606 used, for example, to skip plain text authenticators when the connection is not
25607 encrypted by a setting such as:
25609 client_condition = ${if !eq{$tls_out_cipher}{}}
25613 .option client_set_id authenticators string&!! unset
25614 When client authentication succeeds, this condition is expanded; the
25615 result is used in the log lines for outbound messages.
25616 Typically it will be the user name used for authentication.
25619 .option driver authenticators string unset
25620 This option must always be set. It specifies which of the available
25621 authenticators is to be used.
25624 .option public_name authenticators string unset
25625 This option specifies the name of the authentication mechanism that the driver
25626 implements, and by which it is known to the outside world. These names should
25627 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25628 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25629 defaults to the driver's instance name.
25632 .option server_advertise_condition authenticators string&!! unset
25633 When a server is about to advertise an authentication mechanism, the condition
25634 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25635 mechanism is not advertised.
25636 If the expansion fails, the mechanism is not advertised. If the failure was not
25637 forced, and was not caused by a lookup defer, the incident is logged.
25638 See section &<<SECTauthexiser>>& below for further discussion.
25641 .option server_condition authenticators string&!! unset
25642 This option must be set for a &%plaintext%& server authenticator, where it
25643 is used directly to control authentication. See section &<<SECTplainserver>>&
25646 For the &(gsasl)& authenticator, this option is required for various
25647 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25649 For the other authenticators, &%server_condition%& can be used as an additional
25650 authentication or authorization mechanism that is applied after the other
25651 authenticator conditions succeed. If it is set, it is expanded when the
25652 authenticator would otherwise return a success code. If the expansion is forced
25653 to fail, authentication fails. Any other expansion failure causes a temporary
25654 error code to be returned. If the result of a successful expansion is an empty
25655 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25656 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
25657 other result, a temporary error code is returned, with the expanded string as
25661 .option server_debug_print authenticators string&!! unset
25662 If this option is set and authentication debugging is enabled (see the &%-d%&
25663 command line option), the string is expanded and included in the debugging
25664 output when the authenticator is run as a server. This can help with checking
25665 out the values of variables.
25666 If expansion of the string fails, the error message is written to the debugging
25667 output, and Exim carries on processing.
25670 .option server_set_id authenticators string&!! unset
25671 .vindex "&$authenticated_id$&"
25672 When an Exim server successfully authenticates a client, this string is
25673 expanded using data from the authentication, and preserved for any incoming
25674 messages in the variable &$authenticated_id$&. It is also included in the log
25675 lines for incoming messages. For example, a user/password authenticator
25676 configuration might preserve the user name that was used to authenticate, and
25677 refer to it subsequently during delivery of the message.
25678 If expansion fails, the option is ignored.
25681 .option server_mail_auth_condition authenticators string&!! unset
25682 This option allows a server to discard authenticated sender addresses supplied
25683 as part of MAIL commands in SMTP connections that are authenticated by the
25684 driver on which &%server_mail_auth_condition%& is set. The option is not used
25685 as part of the authentication process; instead its (unexpanded) value is
25686 remembered for later use.
25687 How it is used is described in the following section.
25693 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
25694 .cindex "authentication" "sender; authenticated"
25695 .cindex "AUTH" "on MAIL command"
25696 When a client supplied an AUTH= item on a MAIL command, Exim applies
25697 the following checks before accepting it as the authenticated sender of the
25701 If the connection is not using extended SMTP (that is, HELO was used rather
25702 than EHLO), the use of AUTH= is a syntax error.
25704 If the value of the AUTH= parameter is &"<>"&, it is ignored.
25706 .vindex "&$authenticated_sender$&"
25707 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
25708 running, the value of &$authenticated_sender$& is set to the value obtained
25709 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
25710 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
25711 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
25712 given for the MAIL command.
25714 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
25715 is accepted and placed in &$authenticated_sender$& only if the client has
25718 If the AUTH= value was accepted by either of the two previous rules, and
25719 the client has authenticated, and the authenticator has a setting for the
25720 &%server_mail_auth_condition%&, the condition is checked at this point. The
25721 valued that was saved from the authenticator is expanded. If the expansion
25722 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
25723 &$authenticated_sender$& is deleted. If the expansion yields any other value,
25724 the value of &$authenticated_sender$& is retained and passed on with the
25729 When &$authenticated_sender$& is set for a message, it is passed on to other
25730 hosts to which Exim authenticates as a client. Do not confuse this value with
25731 &$authenticated_id$&, which is a string obtained from the authentication
25732 process, and which is not usually a complete email address.
25734 .vindex "&$sender_address$&"
25735 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
25736 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
25737 therefore make use of &$authenticated_sender$&. The converse is not true: the
25738 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
25743 .section "Authentication on an Exim server" "SECTauthexiser"
25744 .cindex "authentication" "on an Exim server"
25745 When Exim receives an EHLO command, it advertises the public names of those
25746 authenticators that are configured as servers, subject to the following
25750 The client host must match &%auth_advertise_hosts%& (default *).
25752 It the &%server_advertise_condition%& option is set, its expansion must not
25753 yield the empty string, &"0"&, &"no"&, or &"false"&.
25756 The order in which the authenticators are defined controls the order in which
25757 the mechanisms are advertised.
25759 Some mail clients (for example, some versions of Netscape) require the user to
25760 provide a name and password for authentication whenever AUTH is advertised,
25761 even though authentication may not in fact be needed (for example, Exim may be
25762 set up to allow unconditional relaying from the client by an IP address check).
25763 You can make such clients more friendly by not advertising AUTH to them.
25764 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
25765 that runs for RCPT) to relay without authentication, you should set
25767 auth_advertise_hosts = ! 10.9.8.0/24
25769 so that no authentication mechanisms are advertised to them.
25771 The &%server_advertise_condition%& controls the advertisement of individual
25772 authentication mechanisms. For example, it can be used to restrict the
25773 advertisement of a particular mechanism to encrypted connections, by a setting
25776 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
25778 .vindex "&$tls_in_cipher$&"
25779 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
25780 yields &"yes"&, which allows the advertisement to happen.
25782 When an Exim server receives an AUTH command from a client, it rejects it
25783 immediately if AUTH was not advertised in response to an earlier EHLO
25784 command. This is the case if
25787 The client host does not match &%auth_advertise_hosts%&; or
25789 No authenticators are configured with server options; or
25791 Expansion of &%server_advertise_condition%& blocked the advertising of all the
25792 server authenticators.
25796 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
25797 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
25798 AUTH is accepted from any client host.
25800 If AUTH is not rejected by the ACL, Exim searches its configuration for a
25801 server authentication mechanism that was advertised in response to EHLO and
25802 that matches the one named in the AUTH command. If it finds one, it runs
25803 the appropriate authentication protocol, and authentication either succeeds or
25804 fails. If there is no matching advertised mechanism, the AUTH command is
25805 rejected with a 504 error.
25807 .vindex "&$received_protocol$&"
25808 .vindex "&$sender_host_authenticated$&"
25809 When a message is received from an authenticated host, the value of
25810 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
25811 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
25812 public name) of the authenticator driver that successfully authenticated the
25813 client from which the message was received. This variable is empty if there was
25814 no successful authentication.
25819 .section "Testing server authentication" "SECID169"
25820 .cindex "authentication" "testing a server"
25821 .cindex "AUTH" "testing a server"
25822 .cindex "base64 encoding" "creating authentication test data"
25823 Exim's &%-bh%& option can be useful for testing server authentication
25824 configurations. The data for the AUTH command has to be sent using base64
25825 encoding. A quick way to produce such data for testing is the following Perl
25829 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
25831 .cindex "binary zero" "in authentication data"
25832 This interprets its argument as a Perl string, and then encodes it. The
25833 interpretation as a Perl string allows binary zeros, which are required for
25834 some kinds of authentication, to be included in the data. For example, a
25835 command line to run this script on such data might be
25837 encode '\0user\0password'
25839 Note the use of single quotes to prevent the shell interpreting the
25840 backslashes, so that they can be interpreted by Perl to specify characters
25841 whose code value is zero.
25843 &*Warning 1*&: If either of the user or password strings starts with an octal
25844 digit, you must use three zeros instead of one after the leading backslash. If
25845 you do not, the octal digit that starts your string will be incorrectly
25846 interpreted as part of the code for the first character.
25848 &*Warning 2*&: If there are characters in the strings that Perl interprets
25849 specially, you must use a Perl escape to prevent them being misinterpreted. For
25850 example, a command such as
25852 encode '\0user@domain.com\0pas$$word'
25854 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
25856 If you have the &%mimencode%& command installed, another way to do produce
25857 base64-encoded strings is to run the command
25859 echo -e -n `\0user\0password' | mimencode
25861 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
25862 in the argument, and the &%-n%& option specifies no newline at the end of its
25863 output. However, not all versions of &%echo%& recognize these options, so you
25864 should check your version before relying on this suggestion.
25868 .section "Authentication by an Exim client" "SECID170"
25869 .cindex "authentication" "on an Exim client"
25870 The &(smtp)& transport has two options called &%hosts_require_auth%& and
25871 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
25872 announces support for authentication, and the host matches an entry in either
25873 of these options, Exim (as a client) tries to authenticate as follows:
25876 For each authenticator that is configured as a client, in the order in which
25877 they are defined in the configuration, it searches the authentication
25878 mechanisms announced by the server for one whose name matches the public name
25879 of the authenticator.
25882 .vindex "&$host_address$&"
25883 When it finds one that matches, it runs the authenticator's client code. The
25884 variables &$host$& and &$host_address$& are available for any string expansions
25885 that the client might do. They are set to the server's name and IP address. If
25886 any expansion is forced to fail, the authentication attempt is abandoned, and
25887 Exim moves on to the next authenticator. Otherwise an expansion failure causes
25888 delivery to be deferred.
25890 If the result of the authentication attempt is a temporary error or a timeout,
25891 Exim abandons trying to send the message to the host for the moment. It will
25892 try again later. If there are any backup hosts available, they are tried in the
25895 If the response to authentication is a permanent error (5&'xx'& code), Exim
25896 carries on searching the list of authenticators and tries another one if
25897 possible. If all authentication attempts give permanent errors, or if there are
25898 no attempts because no mechanisms match (or option expansions force failure),
25899 what happens depends on whether the host matches &%hosts_require_auth%& or
25900 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
25901 delivery is deferred. The error can be detected in the retry rules, and thereby
25902 turned into a permanent error if you wish. In the second case, Exim tries to
25903 deliver the message unauthenticated.
25906 Note that the hostlist test for whether to do authentication can be
25907 confused if name-IP lookups change between the time the peer is decided
25908 on and the transport running. For example, with a manualroute
25909 router given a host name, and DNS "round-robin" use by that name: if
25910 the local resolver cache times out between the router and the transport
25911 running, the transport may get an IP for the name for its authentication
25912 check which does not match the connection peer IP.
25913 No authentication will then be done, despite the names being identical.
25915 For such cases use a separate transport which always authenticates.
25917 .cindex "AUTH" "on MAIL command"
25918 When Exim has authenticated itself to a remote server, it adds the AUTH
25919 parameter to the MAIL commands it sends, if it has an authenticated sender for
25920 the message. If the message came from a remote host, the authenticated sender
25921 is the one that was receiving on an incoming MAIL command, provided that the
25922 incoming connection was authenticated and the &%server_mail_auth%& condition
25923 allowed the authenticated sender to be retained. If a local process calls Exim
25924 to send a message, the sender address that is built from the login name and
25925 &%qualify_domain%& is treated as authenticated. However, if the
25926 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
25927 the authenticated sender that was received with the message.
25928 .ecindex IIDauthconf1
25929 .ecindex IIDauthconf2
25936 . ////////////////////////////////////////////////////////////////////////////
25937 . ////////////////////////////////////////////////////////////////////////////
25939 .chapter "The plaintext authenticator" "CHAPplaintext"
25940 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
25941 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
25942 The &(plaintext)& authenticator can be configured to support the PLAIN and
25943 LOGIN authentication mechanisms, both of which transfer authentication data as
25944 plain (unencrypted) text (though base64 encoded). The use of plain text is a
25945 security risk; you are strongly advised to insist on the use of SMTP encryption
25946 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
25947 use unencrypted plain text, you should not use the same passwords for SMTP
25948 connections as you do for login accounts.
25950 .section "Plaintext options" "SECID171"
25951 .cindex "options" "&(plaintext)& authenticator (server)"
25952 When configured as a server, &(plaintext)& uses the following options:
25954 .option server_condition authenticators string&!! unset
25955 This is actually a global authentication option, but it must be set in order to
25956 configure the &(plaintext)& driver as a server. Its use is described below.
25958 .option server_prompts plaintext string&!! unset
25959 The contents of this option, after expansion, must be a colon-separated list of
25960 prompt strings. If expansion fails, a temporary authentication rejection is
25963 .section "Using plaintext in a server" "SECTplainserver"
25964 .cindex "AUTH" "in &(plaintext)& authenticator"
25965 .cindex "binary zero" "in &(plaintext)& authenticator"
25966 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
25967 "in &(plaintext)& authenticator"
25968 .vindex "&$auth1$&, &$auth2$&, etc"
25969 .cindex "base64 encoding" "in &(plaintext)& authenticator"
25971 When running as a server, &(plaintext)& performs the authentication test by
25972 expanding a string. The data sent by the client with the AUTH command, or in
25973 response to subsequent prompts, is base64 encoded, and so may contain any byte
25974 values when decoded. If any data is supplied with the command, it is treated as
25975 a list of strings, separated by NULs (binary zeros), the first three of which
25976 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
25977 (neither LOGIN nor PLAIN uses more than three strings).
25979 For compatibility with previous releases of Exim, the values are also placed in
25980 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
25981 variables for this purpose is now deprecated, as it can lead to confusion in
25982 string expansions that also use them for other things.
25984 If there are more strings in &%server_prompts%& than the number of strings
25985 supplied with the AUTH command, the remaining prompts are used to obtain more
25986 data. Each response from the client may be a list of NUL-separated strings.
25988 .vindex "&$authenticated_id$&"
25989 Once a sufficient number of data strings have been received,
25990 &%server_condition%& is expanded. If the expansion is forced to fail,
25991 authentication fails. Any other expansion failure causes a temporary error code
25992 to be returned. If the result of a successful expansion is an empty string,
25993 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25994 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
25995 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
25996 For any other result, a temporary error code is returned, with the expanded
25997 string as the error text
25999 &*Warning*&: If you use a lookup in the expansion to find the user's
26000 password, be sure to make the authentication fail if the user is unknown.
26001 There are good and bad examples at the end of the next section.
26005 .section "The PLAIN authentication mechanism" "SECID172"
26006 .cindex "PLAIN authentication mechanism"
26007 .cindex "authentication" "PLAIN mechanism"
26008 .cindex "binary zero" "in &(plaintext)& authenticator"
26009 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
26010 sent as one item of data (that is, one combined string containing two NUL
26011 separators). The data is sent either as part of the AUTH command, or
26012 subsequently in response to an empty prompt from the server.
26014 The second and third strings are a user name and a corresponding password.
26015 Using a single fixed user name and password as an example, this could be
26016 configured as follows:
26020 public_name = PLAIN
26022 server_condition = \
26023 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
26024 server_set_id = $auth2
26026 Note that the default result strings from &%if%& (&"true"& or an empty string)
26027 are exactly what we want here, so they need not be specified. Obviously, if the
26028 password contains expansion-significant characters such as dollar, backslash,
26029 or closing brace, they have to be escaped.
26031 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
26032 the end of a string list are ignored). If all the data comes as part of the
26033 AUTH command, as is commonly the case, the prompt is not used. This
26034 authenticator is advertised in the response to EHLO as
26038 and a client host can authenticate itself by sending the command
26040 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
26042 As this contains three strings (more than the number of prompts), no further
26043 data is required from the client. Alternatively, the client may just send
26047 to initiate authentication, in which case the server replies with an empty
26048 prompt. The client must respond with the combined data string.
26050 The data string is base64 encoded, as required by the RFC. This example,
26051 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
26052 represents a zero byte. This is split up into three strings, the first of which
26053 is empty. The &%server_condition%& option in the authenticator checks that the
26054 second two are &`username`& and &`mysecret`& respectively.
26056 Having just one fixed user name and password, as in this example, is not very
26057 realistic, though for a small organization with only a handful of
26058 authenticating clients it could make sense.
26060 A more sophisticated instance of this authenticator could use the user name in
26061 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
26062 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
26063 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
26064 This is an incorrect example:
26066 server_condition = \
26067 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
26069 The expansion uses the user name (&$auth2$&) as the key to look up a password,
26070 which it then compares to the supplied password (&$auth3$&). Why is this example
26071 incorrect? It works fine for existing users, but consider what happens if a
26072 non-existent user name is given. The lookup fails, but as no success/failure
26073 strings are given for the lookup, it yields an empty string. Thus, to defeat
26074 the authentication, all a client has to do is to supply a non-existent user
26075 name and an empty password. The correct way of writing this test is:
26077 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
26078 {${if eq{$value}{$auth3}}} {false}}
26080 In this case, if the lookup succeeds, the result is checked; if the lookup
26081 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
26082 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
26083 always fails if its second argument is empty. However, the second way of
26084 writing the test makes the logic clearer.
26087 .section "The LOGIN authentication mechanism" "SECID173"
26088 .cindex "LOGIN authentication mechanism"
26089 .cindex "authentication" "LOGIN mechanism"
26090 The LOGIN authentication mechanism is not documented in any RFC, but is in use
26091 in a number of programs. No data is sent with the AUTH command. Instead, a
26092 user name and password are supplied separately, in response to prompts. The
26093 plaintext authenticator can be configured to support this as in this example:
26097 public_name = LOGIN
26098 server_prompts = User Name : Password
26099 server_condition = \
26100 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
26101 server_set_id = $auth1
26103 Because of the way plaintext operates, this authenticator accepts data supplied
26104 with the AUTH command (in contravention of the specification of LOGIN), but
26105 if the client does not supply it (as is the case for LOGIN clients), the prompt
26106 strings are used to obtain two data items.
26108 Some clients are very particular about the precise text of the prompts. For
26109 example, Outlook Express is reported to recognize only &"Username:"& and
26110 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
26111 strings. It uses the &%ldapauth%& expansion condition to check the user
26112 name and password by binding to an LDAP server:
26116 public_name = LOGIN
26117 server_prompts = Username:: : Password::
26118 server_condition = ${if and{{ \
26121 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
26122 pass=${quote:$auth2} \
26123 ldap://ldap.example.org/} }} }
26124 server_set_id = uid=$auth1,ou=people,o=example.org
26126 We have to check that the username is not empty before using it, because LDAP
26127 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
26128 operator to correctly quote the DN for authentication. However, the basic
26129 &%quote%& operator, rather than any of the LDAP quoting operators, is the
26130 correct one to use for the password, because quoting is needed only to make
26131 the password conform to the Exim syntax. At the LDAP level, the password is an
26132 uninterpreted string.
26135 .section "Support for different kinds of authentication" "SECID174"
26136 A number of string expansion features are provided for the purpose of
26137 interfacing to different ways of user authentication. These include checking
26138 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
26139 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
26145 .section "Using plaintext in a client" "SECID175"
26146 .cindex "options" "&(plaintext)& authenticator (client)"
26147 The &(plaintext)& authenticator has two client options:
26149 .option client_ignore_invalid_base64 plaintext boolean false
26150 If the client receives a server prompt that is not a valid base64 string,
26151 authentication is abandoned by default. However, if this option is set true,
26152 the error in the challenge is ignored and the client sends the response as
26155 .option client_send plaintext string&!! unset
26156 The string is a colon-separated list of authentication data strings. Each
26157 string is independently expanded before being sent to the server. The first
26158 string is sent with the AUTH command; any more strings are sent in response
26159 to prompts from the server. Before each string is expanded, the value of the
26160 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
26161 with &$auth1$& for the first prompt. Up to three prompts are stored in this
26162 way. Thus, the prompt that is received in response to sending the first string
26163 (with the AUTH command) can be used in the expansion of the second string, and
26164 so on. If an invalid base64 string is received when
26165 &%client_ignore_invalid_base64%& is set, an empty string is put in the
26166 &$auth$&<&'n'&> variable.
26168 &*Note*&: You cannot use expansion to create multiple strings, because
26169 splitting takes priority and happens first.
26171 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
26172 the data, further processing is applied to each string before it is sent. If
26173 there are any single circumflex characters in the string, they are converted to
26174 NULs. Should an actual circumflex be required as data, it must be doubled in
26177 This is an example of a client configuration that implements the PLAIN
26178 authentication mechanism with a fixed user name and password:
26182 public_name = PLAIN
26183 client_send = ^username^mysecret
26185 The lack of colons means that the entire text is sent with the AUTH
26186 command, with the circumflex characters converted to NULs. A similar example
26187 that uses the LOGIN mechanism is:
26191 public_name = LOGIN
26192 client_send = : username : mysecret
26194 The initial colon means that the first string is empty, so no data is sent with
26195 the AUTH command itself. The remaining strings are sent in response to
26197 .ecindex IIDplaiauth1
26198 .ecindex IIDplaiauth2
26203 . ////////////////////////////////////////////////////////////////////////////
26204 . ////////////////////////////////////////////////////////////////////////////
26206 .chapter "The cram_md5 authenticator" "CHID9"
26207 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
26208 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
26209 .cindex "CRAM-MD5 authentication mechanism"
26210 .cindex "authentication" "CRAM-MD5 mechanism"
26211 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
26212 sends a challenge string to the client, and the response consists of a user
26213 name and the CRAM-MD5 digest of the challenge string combined with a secret
26214 string (password) which is known to both server and client. Thus, the secret
26215 is not sent over the network as plain text, which makes this authenticator more
26216 secure than &(plaintext)&. However, the downside is that the secret has to be
26217 available in plain text at either end.
26220 .section "Using cram_md5 as a server" "SECID176"
26221 .cindex "options" "&(cram_md5)& authenticator (server)"
26222 This authenticator has one server option, which must be set to configure the
26223 authenticator as a server:
26225 .option server_secret cram_md5 string&!! unset
26226 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
26227 When the server receives the client's response, the user name is placed in
26228 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
26229 obtain the password for that user. The server then computes the CRAM-MD5 digest
26230 that the client should have sent, and checks that it received the correct
26231 string. If the expansion of &%server_secret%& is forced to fail, authentication
26232 fails. If the expansion fails for some other reason, a temporary error code is
26233 returned to the client.
26235 For compatibility with previous releases of Exim, the user name is also placed
26236 in &$1$&. However, the use of this variables for this purpose is now
26237 deprecated, as it can lead to confusion in string expansions that also use
26238 numeric variables for other things.
26240 For example, the following authenticator checks that the user name given by the
26241 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
26242 user name, authentication fails.
26246 public_name = CRAM-MD5
26247 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
26248 server_set_id = $auth1
26250 .vindex "&$authenticated_id$&"
26251 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26252 name in &$authenticated_id$&. A more typical configuration might look up the
26253 secret string in a file, using the user name as the key. For example:
26257 public_name = CRAM-MD5
26258 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26260 server_set_id = $auth1
26262 Note that this expansion explicitly forces failure if the lookup fails
26263 because &$auth1$& contains an unknown user name.
26265 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26266 using the relevant libraries, you need to know the realm to specify in the
26267 lookup and then ask for the &"userPassword"& attribute for that user in that
26272 public_name = CRAM-MD5
26273 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26274 dbmjz{/etc/sasldb2}{$value}fail}
26275 server_set_id = $auth1
26278 .section "Using cram_md5 as a client" "SECID177"
26279 .cindex "options" "&(cram_md5)& authenticator (client)"
26280 When used as a client, the &(cram_md5)& authenticator has two options:
26284 .option client_name cram_md5 string&!! "the primary host name"
26285 This string is expanded, and the result used as the user name data when
26286 computing the response to the server's challenge.
26289 .option client_secret cram_md5 string&!! unset
26290 This option must be set for the authenticator to work as a client. Its value is
26291 expanded and the result used as the secret string when computing the response.
26295 .vindex "&$host_address$&"
26296 Different user names and secrets can be used for different servers by referring
26297 to &$host$& or &$host_address$& in the options. Forced failure of either
26298 expansion string is treated as an indication that this authenticator is not
26299 prepared to handle this case. Exim moves on to the next configured client
26300 authenticator. Any other expansion failure causes Exim to give up trying to
26301 send the message to the current server.
26303 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26308 public_name = CRAM-MD5
26310 client_secret = secret
26312 .ecindex IIDcramauth1
26313 .ecindex IIDcramauth2
26317 . ////////////////////////////////////////////////////////////////////////////
26318 . ////////////////////////////////////////////////////////////////////////////
26320 .chapter "The cyrus_sasl authenticator" "CHID10"
26321 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26322 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26323 .cindex "Cyrus" "SASL library"
26325 The code for this authenticator was provided by Matthew Byng-Maddick of A L
26326 Digital Ltd (&url(http://www.aldigital.co.uk)).
26328 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26329 library implementation of the RFC 2222 (&"Simple Authentication and Security
26330 Layer"&). This library supports a number of authentication mechanisms,
26331 including PLAIN and LOGIN, but also several others that Exim does not support
26332 directly. In particular, there is support for Kerberos authentication.
26334 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26335 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26336 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26337 name of the driver to determine which mechanism to support.
26339 Where access to some kind of secret file is required, for example in GSSAPI
26340 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26341 user, and that the Cyrus SASL library has no way of escalating privileges
26342 by default. You may also find you need to set environment variables,
26343 depending on the driver you are using.
26345 The application name provided by Exim is &"exim"&, so various SASL options may
26346 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26347 Kerberos, note that because of limitations in the GSSAPI interface,
26348 changing the server keytab might need to be communicated down to the Kerberos
26349 layer independently. The mechanism for doing so is dependent upon the Kerberos
26352 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26353 may be set to point to an alternative keytab file. Exim will pass this
26354 variable through from its own inherited environment when started as root or the
26355 Exim user. The keytab file needs to be readable by the Exim user.
26356 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
26357 environment variable. In practice, for those releases, the Cyrus authenticator
26358 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
26359 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
26362 .section "Using cyrus_sasl as a server" "SECID178"
26363 The &(cyrus_sasl)& authenticator has four private options. It puts the username
26364 (on a successful authentication) into &$auth1$&. For compatibility with
26365 previous releases of Exim, the username is also placed in &$1$&. However, the
26366 use of this variable for this purpose is now deprecated, as it can lead to
26367 confusion in string expansions that also use numeric variables for other
26371 .option server_hostname cyrus_sasl string&!! "see below"
26372 This option selects the hostname that is used when communicating with the
26373 library. The default value is &`$primary_hostname`&. It is up to the underlying
26374 SASL plug-in what it does with this data.
26377 .option server_mech cyrus_sasl string "see below"
26378 This option selects the authentication mechanism this driver should use. The
26379 default is the value of the generic &%public_name%& option. This option allows
26380 you to use a different underlying mechanism from the advertised name. For
26384 driver = cyrus_sasl
26385 public_name = X-ANYTHING
26386 server_mech = CRAM-MD5
26387 server_set_id = $auth1
26390 .option server_realm cyrus_sasl string&!! unset
26391 This specifies the SASL realm that the server claims to be in.
26394 .option server_service cyrus_sasl string &`smtp`&
26395 This is the SASL service that the server claims to implement.
26398 For straightforward cases, you do not need to set any of the authenticator's
26399 private options. All you need to do is to specify an appropriate mechanism as
26400 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
26401 PLAIN, you could have two authenticators as follows:
26404 driver = cyrus_sasl
26405 public_name = CRAM-MD5
26406 server_set_id = $auth1
26409 driver = cyrus_sasl
26410 public_name = PLAIN
26411 server_set_id = $auth2
26413 Cyrus SASL does implement the LOGIN authentication method, even though it is
26414 not a standard method. It is disabled by default in the source distribution,
26415 but it is present in many binary distributions.
26416 .ecindex IIDcyrauth1
26417 .ecindex IIDcyrauth2
26422 . ////////////////////////////////////////////////////////////////////////////
26423 . ////////////////////////////////////////////////////////////////////////////
26424 .chapter "The dovecot authenticator" "CHAPdovecot"
26425 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
26426 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
26427 This authenticator is an interface to the authentication facility of the
26428 Dovecot POP/IMAP server, which can support a number of authentication methods.
26429 Note that Dovecot must be configured to use auth-client not auth-userdb.
26430 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
26431 to use the same mechanisms for SMTP authentication. This is a server
26432 authenticator only. There is only one option:
26434 .option server_socket dovecot string unset
26436 This option must specify the socket that is the interface to Dovecot
26437 authentication. The &%public_name%& option must specify an authentication
26438 mechanism that Dovecot is configured to support. You can have several
26439 authenticators for different mechanisms. For example:
26443 public_name = PLAIN
26444 server_socket = /var/run/dovecot/auth-client
26445 server_set_id = $auth1
26450 server_socket = /var/run/dovecot/auth-client
26451 server_set_id = $auth1
26453 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
26454 &$received_ip_address$& (that is, the connection is local), the &"secured"&
26455 option is passed in the Dovecot authentication command. If, for a TLS
26456 connection, a client certificate has been verified, the &"valid-client-cert"&
26457 option is passed. When authentication succeeds, the identity of the user
26458 who authenticated is placed in &$auth1$&.
26459 .ecindex IIDdcotauth1
26460 .ecindex IIDdcotauth2
26463 . ////////////////////////////////////////////////////////////////////////////
26464 . ////////////////////////////////////////////////////////////////////////////
26465 .chapter "The gsasl authenticator" "CHAPgsasl"
26466 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26467 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26468 .cindex "authentication" "GNU SASL"
26469 .cindex "authentication" "SASL"
26470 .cindex "authentication" "EXTERNAL"
26471 .cindex "authentication" "ANONYMOUS"
26472 .cindex "authentication" "PLAIN"
26473 .cindex "authentication" "LOGIN"
26474 .cindex "authentication" "DIGEST-MD5"
26475 .cindex "authentication" "CRAM-MD5"
26476 .cindex "authentication" "SCRAM-SHA-1"
26477 The &(gsasl)& authenticator provides server integration for the GNU SASL
26478 library and the mechanisms it provides. This is new as of the 4.80 release
26479 and there are a few areas where the library does not let Exim smoothly
26480 scale to handle future authentication mechanisms, so no guarantee can be
26481 made that any particular new authentication mechanism will be supported
26482 without code changes in Exim.
26485 .option server_channelbinding gsasl boolean false
26486 Some authentication mechanisms are able to use external context at both ends
26487 of the session to bind the authentication to that context, and fail the
26488 authentication process if that context differs. Specifically, some TLS
26489 ciphersuites can provide identifying information about the cryptographic
26492 This means that certificate identity and verification becomes a non-issue,
26493 as a man-in-the-middle attack will cause the correct client and server to
26494 see different identifiers and authentication will fail.
26496 This is currently only supported when using the GnuTLS library. This is
26497 only usable by mechanisms which support "channel binding"; at time of
26498 writing, that's the SCRAM family.
26500 This defaults off to ensure smooth upgrade across Exim releases, in case
26501 this option causes some clients to start failing. Some future release
26502 of Exim may switch the default to be true.
26505 .option server_hostname gsasl string&!! "see below"
26506 This option selects the hostname that is used when communicating with the
26507 library. The default value is &`$primary_hostname`&.
26508 Some mechanisms will use this data.
26511 .option server_mech gsasl string "see below"
26512 This option selects the authentication mechanism this driver should use. The
26513 default is the value of the generic &%public_name%& option. This option allows
26514 you to use a different underlying mechanism from the advertised name. For
26519 public_name = X-ANYTHING
26520 server_mech = CRAM-MD5
26521 server_set_id = $auth1
26525 .option server_password gsasl string&!! unset
26526 Various mechanisms need access to the cleartext password on the server, so
26527 that proof-of-possession can be demonstrated on the wire, without sending
26528 the password itself.
26530 The data available for lookup varies per mechanism.
26531 In all cases, &$auth1$& is set to the &'authentication id'&.
26532 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26533 if available, else the empty string.
26534 The &$auth3$& variable will always be the &'realm'& if available,
26535 else the empty string.
26537 A forced failure will cause authentication to defer.
26539 If using this option, it may make sense to set the &%server_condition%&
26540 option to be simply "true".
26543 .option server_realm gsasl string&!! unset
26544 This specifies the SASL realm that the server claims to be in.
26545 Some mechanisms will use this data.
26548 .option server_scram_iter gsasl string&!! unset
26549 This option provides data for the SCRAM family of mechanisms.
26550 &$auth1$& is not available at evaluation time.
26551 (This may change, as we receive feedback on use)
26554 .option server_scram_salt gsasl string&!! unset
26555 This option provides data for the SCRAM family of mechanisms.
26556 &$auth1$& is not available at evaluation time.
26557 (This may change, as we receive feedback on use)
26560 .option server_service gsasl string &`smtp`&
26561 This is the SASL service that the server claims to implement.
26562 Some mechanisms will use this data.
26565 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26566 .vindex "&$auth1$&, &$auth2$&, etc"
26567 These may be set when evaluating specific options, as detailed above.
26568 They will also be set when evaluating &%server_condition%&.
26570 Unless otherwise stated below, the &(gsasl)& integration will use the following
26571 meanings for these variables:
26574 .vindex "&$auth1$&"
26575 &$auth1$&: the &'authentication id'&
26577 .vindex "&$auth2$&"
26578 &$auth2$&: the &'authorization id'&
26580 .vindex "&$auth3$&"
26581 &$auth3$&: the &'realm'&
26584 On a per-mechanism basis:
26587 .cindex "authentication" "EXTERNAL"
26588 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26589 the &%server_condition%& option must be present.
26591 .cindex "authentication" "ANONYMOUS"
26592 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26593 the &%server_condition%& option must be present.
26595 .cindex "authentication" "GSSAPI"
26596 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26597 &$auth2$& will be set to the &'authorization id'&,
26598 the &%server_condition%& option must be present.
26601 An &'anonymous token'& is something passed along as an unauthenticated
26602 identifier; this is analogous to FTP anonymous authentication passing an
26603 email address, or software-identifier@, as the "password".
26606 An example showing the password having the realm specified in the callback
26607 and demonstrating a Cyrus SASL to GSASL migration approach is:
26609 gsasl_cyrusless_crammd5:
26611 public_name = CRAM-MD5
26612 server_realm = imap.example.org
26613 server_password = ${lookup{$auth1:$auth3:userPassword}\
26614 dbmjz{/etc/sasldb2}{$value}fail}
26615 server_set_id = ${quote:$auth1}
26616 server_condition = yes
26620 . ////////////////////////////////////////////////////////////////////////////
26621 . ////////////////////////////////////////////////////////////////////////////
26623 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26624 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26625 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26626 .cindex "authentication" "GSSAPI"
26627 .cindex "authentication" "Kerberos"
26628 The &(heimdal_gssapi)& authenticator provides server integration for the
26629 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26632 .option server_hostname heimdal_gssapi string&!! "see below"
26633 This option selects the hostname that is used, with &%server_service%&,
26634 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26635 identifier. The default value is &`$primary_hostname`&.
26637 .option server_keytab heimdal_gssapi string&!! unset
26638 If set, then Heimdal will not use the system default keytab (typically
26639 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26640 The value should be a pathname, with no &"file:"& prefix.
26642 .option server_service heimdal_gssapi string&!! "smtp"
26643 This option specifies the service identifier used, in conjunction with
26644 &%server_hostname%&, for building the identifier for finding credentials
26648 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26649 Beware that these variables will typically include a realm, thus will appear
26650 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26651 not verified, so a malicious client can set it to anything.
26653 The &$auth1$& field should be safely trustable as a value from the Key
26654 Distribution Center. Note that these are not quite email addresses.
26655 Each identifier is for a role, and so the left-hand-side may include a
26656 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
26658 .vindex "&$auth1$&, &$auth2$&, etc"
26660 .vindex "&$auth1$&"
26661 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
26663 .vindex "&$auth2$&"
26664 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
26665 authentication. If that was empty, this will also be set to the
26670 . ////////////////////////////////////////////////////////////////////////////
26671 . ////////////////////////////////////////////////////////////////////////////
26673 .chapter "The spa authenticator" "CHAPspa"
26674 .scindex IIDspaauth1 "&(spa)& authenticator"
26675 .scindex IIDspaauth2 "authenticators" "&(spa)&"
26676 .cindex "authentication" "Microsoft Secure Password"
26677 .cindex "authentication" "NTLM"
26678 .cindex "Microsoft Secure Password Authentication"
26679 .cindex "NTLM authentication"
26680 The &(spa)& authenticator provides client support for Microsoft's &'Secure
26681 Password Authentication'& mechanism,
26682 which is also sometimes known as NTLM (NT LanMan). The code for client side of
26683 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
26684 taken from the Samba project (&url(http://www.samba.org)). The code for the
26685 server side was subsequently contributed by Tom Kistner. The mechanism works as
26689 After the AUTH command has been accepted, the client sends an SPA
26690 authentication request based on the user name and optional domain.
26692 The server sends back a challenge.
26694 The client builds a challenge response which makes use of the user's password
26695 and sends it to the server, which then accepts or rejects it.
26698 Encryption is used to protect the password in transit.
26702 .section "Using spa as a server" "SECID179"
26703 .cindex "options" "&(spa)& authenticator (server)"
26704 The &(spa)& authenticator has just one server option:
26706 .option server_password spa string&!! unset
26707 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
26708 This option is expanded, and the result must be the cleartext password for the
26709 authenticating user, whose name is at this point in &$auth1$&. For
26710 compatibility with previous releases of Exim, the user name is also placed in
26711 &$1$&. However, the use of this variable for this purpose is now deprecated, as
26712 it can lead to confusion in string expansions that also use numeric variables
26713 for other things. For example:
26718 server_password = \
26719 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
26721 If the expansion is forced to fail, authentication fails. Any other expansion
26722 failure causes a temporary error code to be returned.
26728 .section "Using spa as a client" "SECID180"
26729 .cindex "options" "&(spa)& authenticator (client)"
26730 The &(spa)& authenticator has the following client options:
26734 .option client_domain spa string&!! unset
26735 This option specifies an optional domain for the authentication.
26738 .option client_password spa string&!! unset
26739 This option specifies the user's password, and must be set.
26742 .option client_username spa string&!! unset
26743 This option specifies the user name, and must be set. Here is an example of a
26744 configuration of this authenticator for use with the mail servers at
26750 client_username = msn/msn_username
26751 client_password = msn_plaintext_password
26752 client_domain = DOMAIN_OR_UNSET
26754 .ecindex IIDspaauth1
26755 .ecindex IIDspaauth2
26761 . ////////////////////////////////////////////////////////////////////////////
26762 . ////////////////////////////////////////////////////////////////////////////
26764 .chapter "The tls authenticator" "CHAPtlsauth"
26765 .scindex IIDtlsauth1 "&(tls)& authenticator"
26766 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
26767 .cindex "authentication" "Client Certificate"
26768 .cindex "authentication" "X509"
26769 .cindex "Certificate-based authentication"
26770 The &(tls)& authenticator provides server support for
26771 authentication based on client certificates.
26773 It is not an SMTP authentication mechanism and is not
26774 advertised by the server as part of the SMTP EHLO response.
26775 It is an Exim authenticator in the sense that it affects
26776 the protocol element of the log line, can be tested for
26777 by the &%authenticated%& ACL condition, and can set
26778 the &$authenticated_id$& variable.
26780 The client must present a verifiable certificate,
26781 for which it must have been requested via the
26782 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
26783 (see &<<CHAPTLS>>&).
26785 If an authenticator of this type is configured it is
26786 run before any SMTP-level communication is done,
26787 and can authenticate the connection.
26788 If it does, SMTP authentication is not offered.
26790 A maximum of one authenticator of this type may be present.
26793 .cindex "options" "&(tls)& authenticator (server)"
26794 The &(tls)& authenticator has three server options:
26796 .option server_param1 tls string&!! unset
26797 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
26798 This option is expanded after the TLS negotiation and
26799 the result is placed in &$auth1$&.
26800 If the expansion is forced to fail, authentication fails. Any other expansion
26801 failure causes a temporary error code to be returned.
26803 .option server_param2 tls string&!! unset
26804 .option server_param3 tls string&!! unset
26805 As above, for &$auth2$& and &$auth3$&.
26807 &%server_param1%& may also be spelled &%server_param%&.
26814 server_param1 = ${certextract {subj_altname,mail,>:} \
26815 {$tls_in_peercert}}
26816 server_condition = ${if forany {$auth1} \
26818 {${lookup ldap{ldap:///\
26819 mailname=${quote_ldap_dn:${lc:$item}},\
26820 ou=users,LDAP_DC?mailid} {$value}{0} \
26822 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
26824 This accepts a client certificate that is verifiable against any
26825 of your configured trust-anchors
26826 (which usually means the full set of public CAs)
26827 and which has a SAN with a good account name.
26828 Note that the client cert is on the wire in-clear, including the SAN,
26829 whereas a plaintext SMTP AUTH done inside TLS is not.
26831 . An alternative might use
26833 . server_param1 = ${sha256:$tls_in_peercert}
26835 . to require one of a set of specific certs that define a given account
26836 . (the verification is still required, but mostly irrelevant).
26837 . This would help for per-device use.
26839 . However, for the future we really need support for checking a
26840 . user cert in LDAP - which probably wants a base-64 DER.
26842 .ecindex IIDtlsauth1
26843 .ecindex IIDtlsauth2
26846 Note that because authentication is traditionally an SMTP operation,
26847 the &%authenticated%& ACL condition cannot be used in
26848 a connect- or helo-ACL.
26852 . ////////////////////////////////////////////////////////////////////////////
26853 . ////////////////////////////////////////////////////////////////////////////
26855 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
26856 "Encrypted SMTP connections"
26857 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
26858 .scindex IIDencsmtp2 "SMTP" "encryption"
26859 .cindex "TLS" "on SMTP connection"
26862 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
26863 Sockets Layer), is implemented by making use of the OpenSSL library or the
26864 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
26865 cryptographic code in the Exim distribution itself for implementing TLS. In
26866 order to use this feature you must install OpenSSL or GnuTLS, and then build a
26867 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
26868 You also need to understand the basic concepts of encryption at a managerial
26869 level, and in particular, the way that public keys, private keys, and
26870 certificates are used.
26872 RFC 3207 defines how SMTP connections can make use of encryption. Once a
26873 connection is established, the client issues a STARTTLS command. If the
26874 server accepts this, the client and the server negotiate an encryption
26875 mechanism. If the negotiation succeeds, the data that subsequently passes
26876 between them is encrypted.
26878 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
26879 and if so, what cipher suite is in use, whether the client supplied a
26880 certificate, and whether or not that certificate was verified. This makes it
26881 possible for an Exim server to deny or accept certain commands based on the
26884 &*Warning*&: Certain types of firewall and certain anti-virus products can
26885 disrupt TLS connections. You need to turn off SMTP scanning for these products
26886 in order to get TLS to work.
26890 .section "Support for the legacy &""ssmtp""& (aka &""smtps""&) protocol" &&&
26892 .cindex "ssmtp protocol"
26893 .cindex "smtps protocol"
26894 .cindex "SMTP" "ssmtp protocol"
26895 .cindex "SMTP" "smtps protocol"
26896 Early implementations of encrypted SMTP used a different TCP port from normal
26897 SMTP, and expected an encryption negotiation to start immediately, instead of
26898 waiting for a STARTTLS command from the client using the standard SMTP
26899 port. The protocol was called &"ssmtp"& or &"smtps"&, and port 465 was
26900 allocated for this purpose.
26902 This approach was abandoned when encrypted SMTP was standardized, but there are
26903 still some legacy clients that use it. Exim supports these clients by means of
26904 the &%tls_on_connect_ports%& global option. Its value must be a list of port
26905 numbers; the most common use is expected to be:
26907 tls_on_connect_ports = 465
26909 The port numbers specified by this option apply to all SMTP connections, both
26910 via the daemon and via &'inetd'&. You still need to specify all the ports that
26911 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
26912 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
26913 an extra port &-- rather, it specifies different behaviour on a port that is
26916 There is also a &%-tls-on-connect%& command line option. This overrides
26917 &%tls_on_connect_ports%&; it forces the legacy behaviour for all ports.
26924 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
26925 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
26926 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
26927 followed later, when the first versions of GnuTLS were released. To build Exim
26928 to use GnuTLS, you need to set
26932 in Local/Makefile, in addition to
26936 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
26937 include files and libraries for GnuTLS can be found.
26939 There are some differences in usage when using GnuTLS instead of OpenSSL:
26942 The &%tls_verify_certificates%& option
26943 cannot be the path of a directory
26944 for GnuTLS versions before 3.3.6
26945 (for later versions, or OpenSSL, it can be either).
26947 The default value for &%tls_dhparam%& differs for historical reasons.
26949 .vindex "&$tls_in_peerdn$&"
26950 .vindex "&$tls_out_peerdn$&"
26951 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
26952 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
26953 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
26955 OpenSSL identifies cipher suites using hyphens as separators, for example:
26956 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
26957 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
26958 in a cipher list. To make life simpler, Exim changes underscores to hyphens
26959 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
26960 to handle its own older variants) when processing lists of cipher suites in the
26961 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
26964 The &%tls_require_ciphers%& options operate differently, as described in the
26965 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
26967 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
26968 When using OpenSSL, this option is ignored.
26969 (If an API is found to let OpenSSL be configured in this way,
26970 let the Exim Maintainers know and we'll likely use it).
26972 Some other recently added features may only be available in one or the other.
26973 This should be documented with the feature. If the documentation does not
26974 explicitly state that the feature is infeasible in the other TLS
26975 implementation, then patches are welcome.
26979 .section "GnuTLS parameter computation" "SECTgnutlsparam"
26980 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
26981 an explicit path; if the latter, then the text about generation still applies,
26982 but not the chosen filename.
26983 By default, as of Exim 4.80 a hard-coded D-H prime is used.
26984 See the documentation of &%tls_dhparam%& for more information.
26986 GnuTLS uses D-H parameters that may take a substantial amount of time
26987 to compute. It is unreasonable to re-compute them for every TLS session.
26988 Therefore, Exim keeps this data in a file in its spool directory, called
26989 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
26991 The file is owned by the Exim user and is readable only by
26992 its owner. Every Exim process that start up GnuTLS reads the D-H
26993 parameters from this file. If the file does not exist, the first Exim process
26994 that needs it computes the data and writes it to a temporary file which is
26995 renamed once it is complete. It does not matter if several Exim processes do
26996 this simultaneously (apart from wasting a few resources). Once a file is in
26997 place, new Exim processes immediately start using it.
26999 For maximum security, the parameters that are stored in this file should be
27000 recalculated periodically, the frequency depending on your paranoia level.
27001 If you are avoiding using the fixed D-H primes published in RFCs, then you
27002 are concerned about some advanced attacks and will wish to do this; if you do
27003 not regenerate then you might as well stick to the standard primes.
27005 Arranging this is easy in principle; just delete the file when you want new
27006 values to be computed. However, there may be a problem. The calculation of new
27007 parameters needs random numbers, and these are obtained from &_/dev/random_&.
27008 If the system is not very active, &_/dev/random_& may delay returning data
27009 until enough randomness (entropy) is available. This may cause Exim to hang for
27010 a substantial amount of time, causing timeouts on incoming connections.
27012 The solution is to generate the parameters externally to Exim. They are stored
27013 in &_gnutls-params-N_& in PEM format, which means that they can be
27014 generated externally using the &(certtool)& command that is part of GnuTLS.
27016 To replace the parameters with new ones, instead of deleting the file
27017 and letting Exim re-create it, you can generate new parameters using
27018 &(certtool)& and, when this has been done, replace Exim's cache file by
27019 renaming. The relevant commands are something like this:
27022 [ look for file; assume gnutls-params-2236 is the most recent ]
27025 # chown exim:exim new-params
27026 # chmod 0600 new-params
27027 # certtool --generate-dh-params --bits 2236 >>new-params
27028 # openssl dhparam -noout -text -in new-params | head
27029 [ check the first line, make sure it's not more than 2236;
27030 if it is, then go back to the start ("rm") and repeat
27031 until the size generated is at most the size requested ]
27032 # chmod 0400 new-params
27033 # mv new-params gnutls-params-2236
27035 If Exim never has to generate the parameters itself, the possibility of
27036 stalling is removed.
27038 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
27039 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
27040 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
27041 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
27042 and Exim does so. This attempt to remove Exim from TLS policy decisions
27043 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
27044 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
27045 which applies to all D-H usage, client or server. If the value returned by
27046 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
27047 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
27048 limit, which is still much higher than Exim historically used.
27050 The filename and bits used will change as the GnuTLS maintainers change the
27051 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
27052 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
27053 2432 bits, while NSS is limited to 2236 bits.
27055 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
27056 increase the chance of the generated prime actually being within acceptable
27057 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
27058 procedure above. There is no sane procedure available to Exim to double-check
27059 the size of the generated prime, so it might still be too large.
27062 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
27063 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
27064 .oindex "&%tls_require_ciphers%&" "OpenSSL"
27065 There is a function in the OpenSSL library that can be passed a list of cipher
27066 suites before the cipher negotiation takes place. This specifies which ciphers
27067 are acceptable. The list is colon separated and may contain names like
27068 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
27069 directly to this function call.
27070 Many systems will install the OpenSSL manual-pages, so you may have
27071 &'ciphers(1)'& available to you.
27072 The following quotation from the OpenSSL
27073 documentation specifies what forms of item are allowed in the cipher string:
27076 It can consist of a single cipher suite such as RC4-SHA.
27078 It can represent a list of cipher suites containing a certain algorithm,
27079 or cipher suites of a certain type. For example SHA1 represents all
27080 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
27083 Lists of cipher suites can be combined in a single cipher string using
27084 the + character. This is used as a logical and operation. For example
27085 SHA1+DES represents all cipher suites containing the SHA1 and the DES
27089 Each cipher string can be optionally preceded by one of the characters &`!`&,
27092 If &`!`& is used, the ciphers are permanently deleted from the list. The
27093 ciphers deleted can never reappear in the list even if they are explicitly
27096 If &`-`& is used, the ciphers are deleted from the list, but some or all
27097 of the ciphers can be added again by later options.
27099 If &`+`& is used, the ciphers are moved to the end of the list. This
27100 option does not add any new ciphers; it just moves matching existing ones.
27103 If none of these characters is present, the string is interpreted as
27104 a list of ciphers to be appended to the current preference list. If the list
27105 includes any ciphers already present they will be ignored: that is, they will
27106 not be moved to the end of the list.
27109 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
27112 # note single-quotes to get ! past any shell history expansion
27113 $ openssl ciphers 'HIGH:!MD5:!SHA1'
27116 This example will let the library defaults be permitted on the MX port, where
27117 there's probably no identity verification anyway, but ups the ante on the
27118 submission ports where the administrator might have some influence on the
27119 choice of clients used:
27121 # OpenSSL variant; see man ciphers(1)
27122 tls_require_ciphers = ${if =={$received_port}{25}\
27129 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
27131 .cindex "GnuTLS" "specifying parameters for"
27132 .cindex "TLS" "specifying ciphers (GnuTLS)"
27133 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
27134 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
27135 .cindex "TLS" "specifying protocols (GnuTLS)"
27136 .cindex "TLS" "specifying priority string (GnuTLS)"
27137 .oindex "&%tls_require_ciphers%&" "GnuTLS"
27138 The GnuTLS library allows the caller to provide a "priority string", documented
27139 as part of the &[gnutls_priority_init]& function. This is very similar to the
27140 ciphersuite specification in OpenSSL.
27142 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
27143 and controls both protocols and ciphers.
27145 The &%tls_require_ciphers%& option is available both as an global option,
27146 controlling how Exim behaves as a server, and also as an option of the
27147 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
27148 the value is string expanded. The resulting string is not an Exim list and
27149 the string is given to the GnuTLS library, so that Exim does not need to be
27150 aware of future feature enhancements of GnuTLS.
27152 Documentation of the strings accepted may be found in the GnuTLS manual, under
27153 "Priority strings". This is online as
27154 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
27155 but beware that this relates to GnuTLS 3, which may be newer than the version
27156 installed on your system. If you are using GnuTLS 3,
27157 then the example code
27158 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
27159 on that site can be used to test a given string.
27163 # Disable older versions of protocols
27164 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
27167 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
27168 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
27169 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
27171 This example will let the library defaults be permitted on the MX port, where
27172 there's probably no identity verification anyway, and lowers security further
27173 by increasing compatibility; but this ups the ante on the submission ports
27174 where the administrator might have some influence on the choice of clients
27178 tls_require_ciphers = ${if =={$received_port}{25}\
27184 .section "Configuring an Exim server to use TLS" "SECID182"
27185 .cindex "TLS" "configuring an Exim server"
27186 When Exim has been built with TLS support, it advertises the availability of
27187 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
27188 but not to any others. The default value of this option is unset, which means
27189 that STARTTLS is not advertised at all. This default is chosen because you
27190 need to set some other options in order to make TLS available, and also it is
27191 sensible for systems that want to use TLS only as a client.
27193 If a client issues a STARTTLS command and there is some configuration
27194 problem in the server, the command is rejected with a 454 error. If the client
27195 persists in trying to issue SMTP commands, all except QUIT are rejected
27198 554 Security failure
27200 If a STARTTLS command is issued within an existing TLS session, it is
27201 rejected with a 554 error code.
27203 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
27204 must be set to match some hosts. The default is * which matches all hosts.
27206 If this is all you do, TLS encryption will be enabled but not authentication -
27207 meaning that the peer has no assurance it is actually you he is talking to.
27208 You gain protection from a passive sniffer listening on the wire but not
27209 from someone able to intercept the communication.
27211 Further protection requires some further configuration at the server end.
27213 It is rumoured that all existing clients that support TLS/SSL use RSA
27214 encryption. To make this work you need to set, in the server,
27216 tls_certificate = /some/file/name
27217 tls_privatekey = /some/file/name
27219 These options are, in fact, expanded strings, so you can make them depend on
27220 the identity of the client that is connected if you wish. The first file
27221 contains the server's X509 certificate, and the second contains the private key
27222 that goes with it. These files need to be
27223 PEM format and readable by the Exim user, and must
27224 always be given as full path names.
27225 The key must not be password-protected.
27226 They can be the same file if both the
27227 certificate and the key are contained within it. If &%tls_privatekey%& is not
27228 set, or if its expansion is forced to fail or results in an empty string, this
27229 is assumed to be the case. The certificate file may also contain intermediate
27230 certificates that need to be sent to the client to enable it to authenticate
27231 the server's certificate.
27233 If you do not understand about certificates and keys, please try to find a
27234 source of this background information, which is not Exim-specific. (There are a
27235 few comments below in section &<<SECTcerandall>>&.)
27237 &*Note*&: These options do not apply when Exim is operating as a client &--
27238 they apply only in the case of a server. If you need to use a certificate in an
27239 Exim client, you must set the options of the same names in an &(smtp)&
27242 With just these options, an Exim server will be able to use TLS. It does not
27243 require the client to have a certificate (but see below for how to insist on
27244 this). There is one other option that may be needed in other situations. If
27246 tls_dhparam = /some/file/name
27248 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
27249 with the parameters contained in the file.
27250 Set this to &`none`& to disable use of DH entirely, by making no prime
27255 This may also be set to a string identifying a standard prime to be used for
27256 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27257 used is &`ike23`&. There are a few standard primes available, see the
27258 documentation for &%tls_dhparam%& for the complete list.
27264 for a way of generating file data.
27266 The strings supplied for these three options are expanded every time a client
27267 host connects. It is therefore possible to use different certificates and keys
27268 for different hosts, if you so wish, by making use of the client's IP address
27269 in &$sender_host_address$& to control the expansion. If a string expansion is
27270 forced to fail, Exim behaves as if the option is not set.
27272 .cindex "cipher" "logging"
27273 .cindex "log" "TLS cipher"
27274 .vindex "&$tls_in_cipher$&"
27275 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27276 an incoming TLS connection. It is included in the &'Received:'& header of an
27277 incoming message (by default &-- you can, of course, change this), and it is
27278 also included in the log line that records a message's arrival, keyed by
27279 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27280 condition can be used to test for specific cipher suites in ACLs.
27282 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27283 can check the name of the cipher suite and vary their actions accordingly. The
27284 cipher suite names vary, depending on which TLS library is being used. For
27285 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27286 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27287 documentation for more details.
27289 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27290 (again depending on the &%tls_cipher%& log selector).
27293 .section "Requesting and verifying client certificates" "SECID183"
27294 .cindex "certificate" "verification of client"
27295 .cindex "TLS" "client certificate verification"
27296 If you want an Exim server to request a certificate when negotiating a TLS
27297 session with a client, you must set either &%tls_verify_hosts%& or
27298 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
27299 apply to all TLS connections. For any host that matches one of these options,
27300 Exim requests a certificate as part of the setup of the TLS session. The
27301 contents of the certificate are verified by comparing it with a list of
27302 expected certificates.
27303 These may be the system default set (depending on library version),
27304 an explicit file or,
27305 depending on library version, a directory, identified by
27306 &%tls_verify_certificates%&.
27308 A file can contain multiple certificates, concatenated end to end. If a
27311 each certificate must be in a separate file, with a name (or a symbolic link)
27312 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
27313 certificate. You can compute the relevant hash by running the command
27315 openssl x509 -hash -noout -in /cert/file
27317 where &_/cert/file_& contains a single certificate.
27319 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
27320 what happens if the client does not supply a certificate, or if the certificate
27321 does not match any of the certificates in the collection named by
27322 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
27323 attempt to set up a TLS session is aborted, and the incoming connection is
27324 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
27325 session continues. ACLs that run for subsequent SMTP commands can detect the
27326 fact that no certificate was verified, and vary their actions accordingly. For
27327 example, you can insist on a certificate before accepting a message for
27328 relaying, but not when the message is destined for local delivery.
27330 .vindex "&$tls_in_peerdn$&"
27331 When a client supplies a certificate (whether it verifies or not), the value of
27332 the Distinguished Name of the certificate is made available in the variable
27333 &$tls_in_peerdn$& during subsequent processing of the message.
27335 .cindex "log" "distinguished name"
27336 Because it is often a long text string, it is not included in the log line or
27337 &'Received:'& header by default. You can arrange for it to be logged, keyed by
27338 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
27339 &%received_header_text%& to change the &'Received:'& header. When no
27340 certificate is supplied, &$tls_in_peerdn$& is empty.
27343 .section "Revoked certificates" "SECID184"
27344 .cindex "TLS" "revoked certificates"
27345 .cindex "revocation list"
27346 .cindex "certificate" "revocation list"
27347 .cindex "OCSP" "stapling"
27348 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
27349 certificates are revoked. If you have such a list, you can pass it to an Exim
27350 server using the global option called &%tls_crl%& and to an Exim client using
27351 an identically named option for the &(smtp)& transport. In each case, the value
27352 of the option is expanded and must then be the name of a file that contains a
27354 The downside is that clients have to periodically re-download a potentially huge
27355 file from every certificate authority they know of.
27357 The way with most moving parts at query time is Online Certificate
27358 Status Protocol (OCSP), where the client verifies the certificate
27359 against an OCSP server run by the CA. This lets the CA track all
27360 usage of the certs. It requires running software with access to the
27361 private key of the CA, to sign the responses to the OCSP queries. OCSP
27362 is based on HTTP and can be proxied accordingly.
27364 The only widespread OCSP server implementation (known to this writer)
27365 comes as part of OpenSSL and aborts on an invalid request, such as
27366 connecting to the port and then disconnecting. This requires
27367 re-entering the passphrase each time some random client does this.
27369 The third way is OCSP Stapling; in this, the server using a certificate
27370 issued by the CA periodically requests an OCSP proof of validity from
27371 the OCSP server, then serves it up inline as part of the TLS
27372 negotiation. This approach adds no extra round trips, does not let the
27373 CA track users, scales well with number of certs issued by the CA and is
27374 resilient to temporary OCSP server failures, as long as the server
27375 starts retrying to fetch an OCSP proof some time before its current
27376 proof expires. The downside is that it requires server support.
27378 Unless Exim is built with the support disabled,
27379 or with GnuTLS earlier than version 3.3.16 / 3.4.8
27380 support for OCSP stapling is included.
27382 There is a global option called &%tls_ocsp_file%&.
27383 The file specified therein is expected to be in DER format, and contain
27384 an OCSP proof. Exim will serve it as part of the TLS handshake. This
27385 option will be re-expanded for SNI, if the &%tls_certificate%& option
27386 contains &`tls_in_sni`&, as per other TLS options.
27388 Exim does not at this time implement any support for fetching a new OCSP
27389 proof. The burden is on the administrator to handle this, outside of
27390 Exim. The file specified should be replaced atomically, so that the
27391 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
27392 on each connection, so a new file will be handled transparently on the
27395 When built with OpenSSL Exim will check for a valid next update timestamp
27396 in the OCSP proof; if not present, or if the proof has expired, it will be
27399 For the client to be able to verify the stapled OCSP the server must
27400 also supply, in its stapled information, any intermediate
27401 certificates for the chain leading to the OCSP proof from the signer
27402 of the server certificate. There may be zero or one such. These
27403 intermediate certificates should be added to the server OCSP stapling
27404 file named by &%tls_ocsp_file%&.
27406 Note that the proof only covers the terminal server certificate,
27407 not any of the chain from CA to it.
27409 There is no current way to staple a proof for a client certificate.
27412 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
27413 OCSP server is supplied. The server URL may be included in the
27414 server certificate, if the CA is helpful.
27416 One failure mode seen was the OCSP Signer cert expiring before the end
27417 of validity of the OCSP proof. The checking done by Exim/OpenSSL
27418 noted this as invalid overall, but the re-fetch script did not.
27424 .section "Configuring an Exim client to use TLS" "SECID185"
27425 .cindex "cipher" "logging"
27426 .cindex "log" "TLS cipher"
27427 .cindex "log" "distinguished name"
27428 .cindex "TLS" "configuring an Exim client"
27429 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
27430 deliveries as well as to incoming, the latter one causing logging of the
27431 server certificate's DN. The remaining client configuration for TLS is all
27432 within the &(smtp)& transport.
27434 It is not necessary to set any options to have TLS work in the &(smtp)&
27435 transport. If Exim is built with TLS support, and TLS is advertised by a
27436 server, the &(smtp)& transport always tries to start a TLS session. However,
27437 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
27438 transport) to a list of server hosts for which TLS should not be used.
27440 If you do not want Exim to attempt to send messages unencrypted when an attempt
27441 to set up an encrypted connection fails in any way, you can set
27442 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
27443 those hosts, delivery is always deferred if an encrypted connection cannot be
27444 set up. If there are any other hosts for the address, they are tried in the
27447 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
27448 the message unencrypted. It always does this if the response to STARTTLS is
27449 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
27450 session after a success response code, what happens is controlled by the
27451 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
27452 delivery to this host is deferred, and other hosts (if available) are tried. If
27453 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
27454 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
27455 negotiation fails, Exim closes the current connection (because it is in an
27456 unknown state), opens a new one to the same host, and then tries the delivery
27459 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
27460 transport provide the client with a certificate, which is passed to the server
27461 if it requests it. If the server is Exim, it will request a certificate only if
27462 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
27464 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
27465 specifies a collection of expected server certificates.
27466 These may be the system default set (depending on library version),
27468 depending on library version, a directory,
27469 must name a file or,
27470 for OpenSSL only (not GnuTLS), a directory.
27471 The client verifies the server's certificate
27472 against this collection, taking into account any revoked certificates that are
27473 in the list defined by &%tls_crl%&.
27474 Failure to verify fails the TLS connection unless either of the
27475 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27477 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27478 certificate verification to the listed servers. Verification either must
27479 or need not succeed respectively.
27481 The &(smtp)& transport has two OCSP-related options:
27482 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27483 is requested and required for the connection to proceed. The default
27485 &%hosts_request_ocsp%&; a host-list for which (additionally)
27486 a Certificate Status is requested (but not necessarily verified). The default
27487 value is "*" meaning that requests are made unless configured
27490 The host(s) should also be in &%hosts_require_tls%&, and
27491 &%tls_verify_certificates%& configured for the transport,
27492 for OCSP to be relevant.
27495 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27496 list of permitted cipher suites. If either of these checks fails, delivery to
27497 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27498 alternative hosts, if any.
27501 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27502 is operating as a client. Exim does not assume that a server certificate (set
27503 by the global options of the same name) should also be used when operating as a
27507 .vindex "&$host_address$&"
27508 All the TLS options in the &(smtp)& transport are expanded before use, with
27509 &$host$& and &$host_address$& containing the name and address of the server to
27510 which the client is connected. Forced failure of an expansion causes Exim to
27511 behave as if the relevant option were unset.
27513 .vindex &$tls_out_bits$&
27514 .vindex &$tls_out_cipher$&
27515 .vindex &$tls_out_peerdn$&
27516 .vindex &$tls_out_sni$&
27517 Before an SMTP connection is established, the
27518 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27519 variables are emptied. (Until the first connection, they contain the values
27520 that were set when the message was received.) If STARTTLS is subsequently
27521 successfully obeyed, these variables are set to the relevant values for the
27522 outgoing connection.
27526 .section "Use of TLS Server Name Indication" "SECTtlssni"
27527 .cindex "TLS" "Server Name Indication"
27528 .vindex "&$tls_in_sni$&"
27529 .oindex "&%tls_in_sni%&"
27530 With TLS1.0 or above, there is an extension mechanism by which extra
27531 information can be included at various points in the protocol. One of these
27532 extensions, documented in RFC 6066 (and before that RFC 4366) is
27533 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27534 client in the initial handshake, so that the server can examine the servername
27535 within and possibly choose to use different certificates and keys (and more)
27538 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27539 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27542 With SMTP to MX, there are the same problems here as in choosing the identity
27543 against which to validate a certificate: you can't rely on insecure DNS to
27544 provide the identity which you then cryptographically verify. So this will
27545 be of limited use in that environment.
27547 With SMTP to Submission, there is a well-defined hostname which clients are
27548 connecting to and can validate certificates against. Thus clients &*can*&
27549 choose to include this information in the TLS negotiation. If this becomes
27550 wide-spread, then hosters can choose to present different certificates to
27551 different clients. Or even negotiate different cipher suites.
27553 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27554 if not empty, will be sent on a TLS session as part of the handshake. There's
27555 nothing more to it. Choosing a sensible value not derived insecurely is the
27556 only point of caution. The &$tls_out_sni$& variable will be set to this string
27557 for the lifetime of the client connection (including during authentication).
27559 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27560 received from a client.
27561 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27563 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27564 option (prior to expansion) then the following options will be re-expanded
27565 during TLS session handshake, to permit alternative values to be chosen:
27568 .vindex "&%tls_certificate%&"
27569 &%tls_certificate%&
27571 .vindex "&%tls_crl%&"
27574 .vindex "&%tls_privatekey%&"
27577 .vindex "&%tls_verify_certificates%&"
27578 &%tls_verify_certificates%&
27580 .vindex "&%tls_ocsp_file%&"
27584 Great care should be taken to deal with matters of case, various injection
27585 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27586 can always be referenced; it is important to remember that &$tls_in_sni$& is
27587 arbitrary unverified data provided prior to authentication.
27588 Further, the initial certificate is loaded before SNI is arrived, so
27589 an expansion for &%tls_certificate%& must have a default which is used
27590 when &$tls_in_sni$& is empty.
27592 The Exim developers are proceeding cautiously and so far no other TLS options
27595 When Exim is built against OpenSSL, OpenSSL must have been built with support
27596 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27597 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27598 see &`-servername`& in the output, then OpenSSL has support.
27600 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27601 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27602 built, then you have SNI support).
27606 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27608 .cindex "multiple SMTP deliveries with TLS"
27609 .cindex "TLS" "multiple message deliveries"
27610 Exim sends multiple messages down the same TCP/IP connection by starting up
27611 an entirely new delivery process for each message, passing the socket from
27612 one process to the next. This implementation does not fit well with the use
27613 of TLS, because there is quite a lot of state information associated with a TLS
27614 connection, not just a socket identification. Passing all the state information
27615 to a new process is not feasible. Consequently, Exim shuts down an existing TLS
27616 session before passing the socket to a new process. The new process may then
27617 try to start a new TLS session, and if successful, may try to re-authenticate
27618 if AUTH is in use, before sending the next message.
27620 The RFC is not clear as to whether or not an SMTP session continues in clear
27621 after TLS has been shut down, or whether TLS may be restarted again later, as
27622 just described. However, if the server is Exim, this shutdown and
27623 reinitialization works. It is not known which (if any) other servers operate
27624 successfully if the client closes a TLS session and continues with unencrypted
27625 SMTP, but there are certainly some that do not work. For such servers, Exim
27626 should not pass the socket to another process, because the failure of the
27627 subsequent attempt to use it would cause Exim to record a temporary host error,
27628 and delay other deliveries to that host.
27630 To test for this case, Exim sends an EHLO command to the server after
27631 closing down the TLS session. If this fails in any way, the connection is
27632 closed instead of being passed to a new delivery process, but no retry
27633 information is recorded.
27635 There is also a manual override; you can set &%hosts_nopass_tls%& on the
27636 &(smtp)& transport to match those hosts for which Exim should not pass
27637 connections to new processes if TLS has been used.
27642 .section "Certificates and all that" "SECTcerandall"
27643 .cindex "certificate" "references to discussion"
27644 In order to understand fully how TLS works, you need to know about
27645 certificates, certificate signing, and certificate authorities. This is not the
27646 place to give a tutorial, especially as I do not know very much about it
27647 myself. Some helpful introduction can be found in the FAQ for the SSL addition
27648 to Apache, currently at
27650 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
27652 Other parts of the &'modssl'& documentation are also helpful, and have
27653 links to further files.
27654 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
27655 0-201-61598-3), contains both introductory and more in-depth descriptions.
27656 Some sample programs taken from the book are available from
27658 &url(http://www.rtfm.com/openssl-examples/)
27662 .section "Certificate chains" "SECID186"
27663 The file named by &%tls_certificate%& may contain more than one
27664 certificate. This is useful in the case where the certificate that is being
27665 sent is validated by an intermediate certificate which the other end does
27666 not have. Multiple certificates must be in the correct order in the file.
27667 First the host's certificate itself, then the first intermediate
27668 certificate to validate the issuer of the host certificate, then the next
27669 intermediate certificate to validate the issuer of the first intermediate
27670 certificate, and so on, until finally (optionally) the root certificate.
27671 The root certificate must already be trusted by the recipient for
27672 validation to succeed, of course, but if it's not preinstalled, sending the
27673 root certificate along with the rest makes it available for the user to
27674 install if the receiving end is a client MUA that can interact with a user.
27676 Note that certificates using MD5 are unlikely to work on today's Internet;
27677 even if your libraries allow loading them for use in Exim when acting as a
27678 server, increasingly clients will not accept such certificates. The error
27679 diagnostics in such a case can be frustratingly vague.
27683 .section "Self-signed certificates" "SECID187"
27684 .cindex "certificate" "self-signed"
27685 You can create a self-signed certificate using the &'req'& command provided
27686 with OpenSSL, like this:
27687 . ==== Do not shorten the duration here without reading and considering
27688 . ==== the text below. Please leave it at 9999 days.
27690 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
27693 &_file1_& and &_file2_& can be the same file; the key and the certificate are
27694 delimited and so can be identified independently. The &%-days%& option
27695 specifies a period for which the certificate is valid. The &%-nodes%& option is
27696 important: if you do not set it, the key is encrypted with a passphrase
27697 that you are prompted for, and any use that is made of the key causes more
27698 prompting for the passphrase. This is not helpful if you are going to use
27699 this certificate and key in an MTA, where prompting is not possible.
27701 . ==== I expect to still be working 26 years from now. The less technical
27702 . ==== debt I create, in terms of storing up trouble for my later years, the
27703 . ==== happier I will be then. We really have reached the point where we
27704 . ==== should start, at the very least, provoking thought and making folks
27705 . ==== pause before proceeding, instead of leaving all the fixes until two
27706 . ==== years before 2^31 seconds after the 1970 Unix epoch.
27708 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
27709 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
27710 the above command might produce a date in the past. Think carefully about
27711 the lifetime of the systems you're deploying, and either reduce the duration
27712 of the certificate or reconsider your platform deployment. (At time of
27713 writing, reducing the duration is the most likely choice, but the inexorable
27714 progression of time takes us steadily towards an era where this will not
27715 be a sensible resolution).
27717 A self-signed certificate made in this way is sufficient for testing, and
27718 may be adequate for all your requirements if you are mainly interested in
27719 encrypting transfers, and not in secure identification.
27721 However, many clients require that the certificate presented by the server be a
27722 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
27723 certificate. In this situation, the self-signed certificate described above
27724 must be installed on the client host as a trusted root &'certification
27725 authority'& (CA), and the certificate used by Exim must be a user certificate
27726 signed with that self-signed certificate.
27728 For information on creating self-signed CA certificates and using them to sign
27729 user certificates, see the &'General implementation overview'& chapter of the
27730 Open-source PKI book, available online at
27731 &url(http://ospkibook.sourceforge.net/).
27732 .ecindex IIDencsmtp1
27733 .ecindex IIDencsmtp2
27737 . ////////////////////////////////////////////////////////////////////////////
27738 . ////////////////////////////////////////////////////////////////////////////
27740 .chapter "Access control lists" "CHAPACL"
27741 .scindex IIDacl "&ACL;" "description"
27742 .cindex "control of incoming mail"
27743 .cindex "message" "controlling incoming"
27744 .cindex "policy control" "access control lists"
27745 Access Control Lists (ACLs) are defined in a separate section of the run time
27746 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
27747 name, terminated by a colon. Here is a complete ACL section that contains just
27748 one very small ACL:
27752 accept hosts = one.host.only
27754 You can have as many lists as you like in the ACL section, and the order in
27755 which they appear does not matter. The lists are self-terminating.
27757 The majority of ACLs are used to control Exim's behaviour when it receives
27758 certain SMTP commands. This applies both to incoming TCP/IP connections, and
27759 when a local process submits a message using SMTP by specifying the &%-bs%&
27760 option. The most common use is for controlling which recipients are accepted
27761 in incoming messages. In addition, you can define an ACL that is used to check
27762 local non-SMTP messages. The default configuration file contains an example of
27763 a realistic ACL for checking RCPT commands. This is discussed in chapter
27764 &<<CHAPdefconfil>>&.
27767 .section "Testing ACLs" "SECID188"
27768 The &%-bh%& command line option provides a way of testing your ACL
27769 configuration locally by running a fake SMTP session with which you interact.
27772 .section "Specifying when ACLs are used" "SECID189"
27773 .cindex "&ACL;" "options for specifying"
27774 In order to cause an ACL to be used, you have to name it in one of the relevant
27775 options in the main part of the configuration. These options are:
27776 .cindex "AUTH" "ACL for"
27777 .cindex "DATA" "ACLs for"
27778 .cindex "ETRN" "ACL for"
27779 .cindex "EXPN" "ACL for"
27780 .cindex "HELO" "ACL for"
27781 .cindex "EHLO" "ACL for"
27782 .cindex "DKIM" "ACL for"
27783 .cindex "MAIL" "ACL for"
27784 .cindex "QUIT, ACL for"
27785 .cindex "RCPT" "ACL for"
27786 .cindex "STARTTLS, ACL for"
27787 .cindex "VRFY" "ACL for"
27788 .cindex "SMTP" "connection, ACL for"
27789 .cindex "non-SMTP messages" "ACLs for"
27790 .cindex "MIME content scanning" "ACL for"
27791 .cindex "PRDR" "ACL for"
27794 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
27795 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
27796 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
27797 .irow &%acl_smtp_auth%& "ACL for AUTH"
27798 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
27799 .irow &%acl_smtp_data%& "ACL after DATA is complete"
27800 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
27801 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
27802 .irow &%acl_smtp_etrn%& "ACL for ETRN"
27803 .irow &%acl_smtp_expn%& "ACL for EXPN"
27804 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
27805 .irow &%acl_smtp_mail%& "ACL for MAIL"
27806 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
27807 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
27808 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
27809 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
27810 .irow &%acl_smtp_quit%& "ACL for QUIT"
27811 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
27812 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
27813 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
27816 For example, if you set
27818 acl_smtp_rcpt = small_acl
27820 the little ACL defined above is used whenever Exim receives a RCPT command
27821 in an SMTP dialogue. The majority of policy tests on incoming messages can be
27822 done when RCPT commands arrive. A rejection of RCPT should cause the
27823 sending MTA to give up on the recipient address contained in the RCPT
27824 command, whereas rejection at other times may cause the client MTA to keep on
27825 trying to deliver the message. It is therefore recommended that you do as much
27826 testing as possible at RCPT time.
27829 .section "The non-SMTP ACLs" "SECID190"
27830 .cindex "non-SMTP messages" "ACLs for"
27831 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
27832 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
27833 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
27834 the state of the SMTP connection such as encryption and authentication) are not
27835 relevant and are forbidden in these ACLs. However, the sender and recipients
27836 are known, so the &%senders%& and &%sender_domains%& conditions and the
27837 &$sender_address$& and &$recipients$& variables can be used. Variables such as
27838 &$authenticated_sender$& are also available. You can specify added header lines
27839 in any of these ACLs.
27841 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
27842 non-SMTP message, before any of the message has been read. (This is the
27843 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
27844 batched SMTP input, it runs after the DATA command has been reached. The
27845 result of this ACL is ignored; it cannot be used to reject a message. If you
27846 really need to, you could set a value in an ACL variable here and reject based
27847 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
27848 controls, and in particular, it can be used to set
27850 control = suppress_local_fixups
27852 This cannot be used in the other non-SMTP ACLs because by the time they are
27853 run, it is too late.
27855 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
27856 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27858 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
27859 kind of rejection is treated as permanent, because there is no way of sending a
27860 temporary error for these kinds of message.
27863 .section "The SMTP connect ACL" "SECID191"
27864 .cindex "SMTP" "connection, ACL for"
27865 .oindex &%smtp_banner%&
27866 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
27867 session, after the test specified by &%host_reject_connection%& (which is now
27868 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
27869 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
27870 the message override the banner message that is otherwise specified by the
27871 &%smtp_banner%& option.
27874 .section "The EHLO/HELO ACL" "SECID192"
27875 .cindex "EHLO" "ACL for"
27876 .cindex "HELO" "ACL for"
27877 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
27878 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
27879 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
27880 Note that a client may issue more than one EHLO or HELO command in an SMTP
27881 session, and indeed is required to issue a new EHLO or HELO after successfully
27882 setting up encryption following a STARTTLS command.
27884 Note also that a deny neither forces the client to go away nor means that
27885 mail will be refused on the connection. Consider checking for
27886 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
27888 If the command is accepted by an &%accept%& verb that has a &%message%&
27889 modifier, the message may not contain more than one line (it will be truncated
27890 at the first newline and a panic logged if it does). Such a message cannot
27891 affect the EHLO options that are listed on the second and subsequent lines of
27895 .section "The DATA ACLs" "SECID193"
27896 .cindex "DATA" "ACLs for"
27897 Two ACLs are associated with the DATA command, because it is two-stage
27898 command, with two responses being sent to the client.
27899 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
27900 is obeyed. This gives you control after all the RCPT commands, but before
27901 the message itself is received. It offers the opportunity to give a negative
27902 response to the DATA command before the data is transmitted. Header lines
27903 added by MAIL or RCPT ACLs are not visible at this time, but any that
27904 are defined here are visible when the &%acl_smtp_data%& ACL is run.
27906 You cannot test the contents of the message, for example, to verify addresses
27907 in the headers, at RCPT time or when the DATA command is received. Such
27908 tests have to appear in the ACL that is run after the message itself has been
27909 received, before the final response to the DATA command is sent. This is
27910 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
27911 associated with the DATA command.
27913 .cindex CHUNKING "BDAT command"
27914 .cindex BDAT "SMTP command"
27915 .cindex "RFC 3030" CHUNKING
27916 If CHUNKING was advertised and a BDAT command sequence is received,
27917 the &%acl_smtp_predata%& ACL is not run.
27918 . XXX why not? It should be possible, for the first BDAT.
27919 The &%acl_smtp_data%& is run after the last BDAT command and all of
27920 the data specified is received.
27922 For both of these ACLs, it is not possible to reject individual recipients. An
27923 error response rejects the entire message. Unfortunately, it is known that some
27924 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
27925 before or after the data) correctly &-- they keep the message on their queues
27926 and try again later, but that is their problem, though it does waste some of
27929 The &%acl_smtp_data%& ACL is run after
27930 the &%acl_smtp_data_prdr%&,
27931 the &%acl_smtp_dkim%&
27932 and the &%acl_smtp_mime%& ACLs.
27934 .section "The SMTP DKIM ACL" "SECTDKIMACL"
27935 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
27936 enabled (which is the default).
27938 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
27939 received, and is executed for each DKIM signature found in a message. If not
27940 otherwise specified, the default action is to accept.
27942 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
27944 For details on the operation of DKIM, see chapter &<<CHAPdkim>>&.
27947 .section "The SMTP MIME ACL" "SECID194"
27948 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
27949 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
27951 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27954 .section "The SMTP PRDR ACL" "SECTPRDRACL"
27955 .cindex "PRDR" "ACL for"
27956 .oindex "&%prdr_enable%&"
27957 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
27958 with PRDR support enabled (which is the default).
27959 It becomes active only when the PRDR feature is negotiated between
27960 client and server for a message, and more than one recipient
27963 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
27964 has been received, and is executed once for each recipient of the message
27965 with &$local_part$& and &$domain$& valid.
27966 The test may accept, defer or deny for individual recipients.
27967 The &%acl_smtp_data%& will still be called after this ACL and
27968 can reject the message overall, even if this ACL has accepted it
27969 for some or all recipients.
27971 PRDR may be used to support per-user content filtering. Without it
27972 one must defer any recipient after the first that has a different
27973 content-filter configuration. With PRDR, the RCPT-time check
27974 .cindex "PRDR" "variable for"
27975 for this can be disabled when the variable &$prdr_requested$&
27977 Any required difference in behaviour of the main DATA-time
27978 ACL should however depend on the PRDR-time ACL having run, as Exim
27979 will avoid doing so in some situations (e.g. single-recipient mails).
27981 See also the &%prdr_enable%& global option
27982 and the &%hosts_try_prdr%& smtp transport option.
27984 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
27985 If the ACL is not defined, processing completes as if
27986 the feature was not requested by the client.
27988 .section "The QUIT ACL" "SECTQUITACL"
27989 .cindex "QUIT, ACL for"
27990 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
27991 does not affect the response code to QUIT, which is always 221. Thus, the ACL
27992 does not in fact control any access.
27993 For this reason, it may only accept
27994 or warn as its final result.
27996 This ACL can be used for tasks such as custom logging at the end of an SMTP
27997 session. For example, you can use ACL variables in other ACLs to count
27998 messages, recipients, etc., and log the totals at QUIT time using one or
27999 more &%logwrite%& modifiers on a &%warn%& verb.
28001 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
28002 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
28004 You do not need to have a final &%accept%&, but if you do, you can use a
28005 &%message%& modifier to specify custom text that is sent as part of the 221
28008 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
28009 failure (for example, failure to open a log file, or when Exim is bombing out
28010 because it has detected an unrecoverable error), all SMTP commands from the
28011 client are given temporary error responses until QUIT is received or the
28012 connection is closed. In these special cases, the QUIT ACL does not run.
28015 .section "The not-QUIT ACL" "SECTNOTQUITACL"
28016 .vindex &$acl_smtp_notquit$&
28017 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
28018 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
28019 trouble, such as being unable to write to its log files, this ACL is not run,
28020 because it might try to do things (such as write to log files) that make the
28021 situation even worse.
28023 Like the QUIT ACL, this ACL is provided to make it possible to do customized
28024 logging or to gather statistics, and its outcome is ignored. The &%delay%&
28025 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
28028 .vindex &$smtp_notquit_reason$&
28029 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
28030 to a string that indicates the reason for the termination of the SMTP
28031 connection. The possible values are:
28033 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
28034 .irow &`bad-commands`& "Too many unknown or non-mail commands"
28035 .irow &`command-timeout`& "Timeout while reading SMTP commands"
28036 .irow &`connection-lost`& "The SMTP connection has been lost"
28037 .irow &`data-timeout`& "Timeout while reading message data"
28038 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
28039 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
28040 .irow &`signal-exit`& "SIGTERM or SIGINT"
28041 .irow &`synchronization-error`& "SMTP synchronization error"
28042 .irow &`tls-failed`& "TLS failed to start"
28044 In most cases when an SMTP connection is closed without having received QUIT,
28045 Exim sends an SMTP response message before actually closing the connection.
28046 With the exception of the &`acl-drop`& case, the default message can be
28047 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
28048 &%drop%& verb in another ACL, it is the message from the other ACL that is
28052 .section "Finding an ACL to use" "SECID195"
28053 .cindex "&ACL;" "finding which to use"
28054 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
28055 you can use different ACLs in different circumstances. For example,
28057 acl_smtp_rcpt = ${if ={25}{$interface_port} \
28058 {acl_check_rcpt} {acl_check_rcpt_submit} }
28060 In the default configuration file there are some example settings for
28061 providing an RFC 4409 message submission service on port 587 and a
28062 non-standard &"smtps"& service on port 465. You can use a string
28063 expansion like this to choose an ACL for MUAs on these ports which is
28064 more appropriate for this purpose than the default ACL on port 25.
28066 The expanded string does not have to be the name of an ACL in the
28067 configuration file; there are other possibilities. Having expanded the
28068 string, Exim searches for an ACL as follows:
28071 If the string begins with a slash, Exim uses it as a file name, and reads its
28072 contents as an ACL. The lines are processed in the same way as lines in the
28073 Exim configuration file. In particular, continuation lines are supported, blank
28074 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
28075 If the file does not exist or cannot be read, an error occurs (typically
28076 causing a temporary failure of whatever caused the ACL to be run). For example:
28078 acl_smtp_data = /etc/acls/\
28079 ${lookup{$sender_host_address}lsearch\
28080 {/etc/acllist}{$value}{default}}
28082 This looks up an ACL file to use on the basis of the host's IP address, falling
28083 back to a default if the lookup fails. If an ACL is successfully read from a
28084 file, it is retained in memory for the duration of the Exim process, so that it
28085 can be re-used without having to re-read the file.
28087 If the string does not start with a slash, and does not contain any spaces,
28088 Exim searches the ACL section of the configuration for an ACL whose name
28089 matches the string.
28091 If no named ACL is found, or if the string contains spaces, Exim parses
28092 the string as an inline ACL. This can save typing in cases where you just
28093 want to have something like
28095 acl_smtp_vrfy = accept
28097 in order to allow free use of the VRFY command. Such a string may contain
28098 newlines; it is processed in the same way as an ACL that is read from a file.
28104 .section "ACL return codes" "SECID196"
28105 .cindex "&ACL;" "return codes"
28106 Except for the QUIT ACL, which does not affect the SMTP return code (see
28107 section &<<SECTQUITACL>>& above), the result of running an ACL is either
28108 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
28109 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
28110 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
28111 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
28112 This also causes a 4&'xx'& return code.
28114 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
28115 &"deny"&, because there is no mechanism for passing temporary errors to the
28116 submitters of non-SMTP messages.
28119 ACLs that are relevant to message reception may also return &"discard"&. This
28120 has the effect of &"accept"&, but causes either the entire message or an
28121 individual recipient address to be discarded. In other words, it is a
28122 blackholing facility. Use it with care.
28124 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
28125 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
28126 RCPT ACL is to discard just the one recipient address. If there are no
28127 recipients left when the message's data is received, the DATA ACL is not
28128 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
28129 remaining recipients. The &"discard"& return is not permitted for the
28130 &%acl_smtp_predata%& ACL.
28132 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
28133 is done on the address and the result determines the SMTP response.
28136 .cindex "&[local_scan()]& function" "when all recipients discarded"
28137 The &[local_scan()]& function is always run, even if there are no remaining
28138 recipients; it may create new recipients.
28142 .section "Unset ACL options" "SECID197"
28143 .cindex "&ACL;" "unset options"
28144 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
28145 all the same. &*Note*&: These defaults apply only when the relevant ACL is
28146 not defined at all. For any defined ACL, the default action when control
28147 reaches the end of the ACL statements is &"deny"&.
28149 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
28150 these two are ACLs that are used only for their side effects. They cannot be
28151 used to accept or reject anything.
28153 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
28154 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
28155 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
28156 when the ACL is not defined is &"accept"&.
28158 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
28159 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
28160 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
28161 messages over an SMTP connection. For an example, see the ACL in the default
28162 configuration file.
28167 .section "Data for message ACLs" "SECID198"
28168 .cindex "&ACL;" "data for message ACL"
28170 .vindex &$local_part$&
28171 .vindex &$sender_address$&
28172 .vindex &$sender_host_address$&
28173 .vindex &$smtp_command$&
28174 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
28175 that contain information about the host and the message's sender (for example,
28176 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
28177 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
28178 &$local_part$& are set from the argument address. The entire SMTP command
28179 is available in &$smtp_command$&.
28181 When an ACL for the AUTH parameter of MAIL is running, the variables that
28182 contain information about the host are set, but &$sender_address$& is not yet
28183 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
28186 .vindex "&$message_size$&"
28187 The &$message_size$& variable is set to the value of the SIZE parameter on
28188 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
28189 that parameter is not given. The value is updated to the true message size by
28190 the time the final DATA ACL is run (after the message data has been
28193 .vindex "&$rcpt_count$&"
28194 .vindex "&$recipients_count$&"
28195 The &$rcpt_count$& variable increases by one for each RCPT command received.
28196 The &$recipients_count$& variable increases by one each time a RCPT command is
28197 accepted, so while an ACL for RCPT is being processed, it contains the number
28198 of previously accepted recipients. At DATA time (for both the DATA ACLs),
28199 &$rcpt_count$& contains the total number of RCPT commands, and
28200 &$recipients_count$& contains the total number of accepted recipients.
28206 .section "Data for non-message ACLs" "SECTdatfornon"
28207 .cindex "&ACL;" "data for non-message ACL"
28208 .vindex &$smtp_command_argument$&
28209 .vindex &$smtp_command$&
28210 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
28211 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
28212 and the entire SMTP command is available in &$smtp_command$&.
28213 These variables can be tested using a &%condition%& condition. For example,
28214 here is an ACL for use with AUTH, which insists that either the session is
28215 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
28216 does not permit authentication methods that use cleartext passwords on
28217 unencrypted connections.
28220 accept encrypted = *
28221 accept condition = ${if eq{${uc:$smtp_command_argument}}\
28223 deny message = TLS encryption or CRAM-MD5 required
28225 (Another way of applying this restriction is to arrange for the authenticators
28226 that use cleartext passwords not to be advertised when the connection is not
28227 encrypted. You can use the generic &%server_advertise_condition%& authenticator
28228 option to do this.)
28232 .section "Format of an ACL" "SECID199"
28233 .cindex "&ACL;" "format of"
28234 .cindex "&ACL;" "verbs, definition of"
28235 An individual ACL consists of a number of statements. Each statement starts
28236 with a verb, optionally followed by a number of conditions and &"modifiers"&.
28237 Modifiers can change the way the verb operates, define error and log messages,
28238 set variables, insert delays, and vary the processing of accepted messages.
28240 If all the conditions are met, the verb is obeyed. The same condition may be
28241 used (with different arguments) more than once in the same statement. This
28242 provides a means of specifying an &"and"& conjunction between conditions. For
28245 deny dnslists = list1.example
28246 dnslists = list2.example
28248 If there are no conditions, the verb is always obeyed. Exim stops evaluating
28249 the conditions and modifiers when it reaches a condition that fails. What
28250 happens then depends on the verb (and in one case, on a special modifier). Not
28251 all the conditions make sense at every testing point. For example, you cannot
28252 test a sender address in the ACL that is run for a VRFY command.
28255 .section "ACL verbs" "SECID200"
28256 The ACL verbs are as follows:
28259 .cindex "&%accept%& ACL verb"
28260 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
28261 of the conditions are not met, what happens depends on whether &%endpass%&
28262 appears among the conditions (for syntax see below). If the failing condition
28263 is before &%endpass%&, control is passed to the next ACL statement; if it is
28264 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
28265 check a RCPT command:
28267 accept domains = +local_domains
28271 If the recipient domain does not match the &%domains%& condition, control
28272 passes to the next statement. If it does match, the recipient is verified, and
28273 the command is accepted if verification succeeds. However, if verification
28274 fails, the ACL yields &"deny"&, because the failing condition is after
28277 The &%endpass%& feature has turned out to be confusing to many people, so its
28278 use is not recommended nowadays. It is always possible to rewrite an ACL so
28279 that &%endpass%& is not needed, and it is no longer used in the default
28282 .cindex "&%message%& ACL modifier" "with &%accept%&"
28283 If a &%message%& modifier appears on an &%accept%& statement, its action
28284 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
28285 (when an &%accept%& verb either accepts or passes control to the next
28286 statement), &%message%& can be used to vary the message that is sent when an
28287 SMTP command is accepted. For example, in a RCPT ACL you could have:
28289 &`accept `&<&'some conditions'&>
28290 &` message = OK, I will allow you through today`&
28292 You can specify an SMTP response code, optionally followed by an &"extended
28293 response code"& at the start of the message, but the first digit must be the
28294 same as would be sent by default, which is 2 for an &%accept%& verb.
28296 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
28297 an error message that is used when access is denied. This behaviour is retained
28298 for backward compatibility, but current &"best practice"& is to avoid the use
28303 .cindex "&%defer%& ACL verb"
28304 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
28305 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
28306 &%defer%& is the same as &%deny%&, because there is no way of sending a
28307 temporary error. For a RCPT command, &%defer%& is much the same as using a
28308 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
28309 be used in any ACL, and even for a recipient it might be a simpler approach.
28313 .cindex "&%deny%& ACL verb"
28314 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
28315 the conditions are not met, control is passed to the next ACL statement. For
28318 deny dnslists = blackholes.mail-abuse.org
28320 rejects commands from hosts that are on a DNS black list.
28324 .cindex "&%discard%& ACL verb"
28325 &%discard%&: This verb behaves like &%accept%&, except that it returns
28326 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
28327 that are concerned with receiving messages. When all the conditions are true,
28328 the sending entity receives a &"success"& response. However, &%discard%& causes
28329 recipients to be discarded. If it is used in an ACL for RCPT, just the one
28330 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
28331 message's recipients are discarded. Recipients that are discarded before DATA
28332 do not appear in the log line when the &%received_recipients%& log selector is set.
28334 If the &%log_message%& modifier is set when &%discard%& operates,
28335 its contents are added to the line that is automatically written to the log.
28336 The &%message%& modifier operates exactly as it does for &%accept%&.
28340 .cindex "&%drop%& ACL verb"
28341 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
28342 forcibly closed after the 5&'xx'& error message has been sent. For example:
28344 drop message = I don't take more than 20 RCPTs
28345 condition = ${if > {$rcpt_count}{20}}
28347 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
28348 The connection is always dropped after sending a 550 response.
28351 .cindex "&%require%& ACL verb"
28352 &%require%&: If all the conditions are met, control is passed to the next ACL
28353 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
28354 example, when checking a RCPT command,
28356 require message = Sender did not verify
28359 passes control to subsequent statements only if the message's sender can be
28360 verified. Otherwise, it rejects the command. Note the positioning of the
28361 &%message%& modifier, before the &%verify%& condition. The reason for this is
28362 discussed in section &<<SECTcondmodproc>>&.
28365 .cindex "&%warn%& ACL verb"
28366 &%warn%&: If all the conditions are true, a line specified by the
28367 &%log_message%& modifier is written to Exim's main log. Control always passes
28368 to the next ACL statement. If any condition is false, the log line is not
28369 written. If an identical log line is requested several times in the same
28370 message, only one copy is actually written to the log. If you want to force
28371 duplicates to be written, use the &%logwrite%& modifier instead.
28373 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
28374 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
28375 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
28376 first failing condition. There is more about adding header lines in section
28377 &<<SECTaddheadacl>>&.
28379 If any condition on a &%warn%& statement cannot be completed (that is, there is
28380 some sort of defer), the log line specified by &%log_message%& is not written.
28381 This does not include the case of a forced failure from a lookup, which
28382 is considered to be a successful completion. After a defer, no further
28383 conditions or modifiers in the &%warn%& statement are processed. The incident
28384 is logged, and the ACL continues to be processed, from the next statement
28388 .vindex "&$acl_verify_message$&"
28389 When one of the &%warn%& conditions is an address verification that fails, the
28390 text of the verification failure message is in &$acl_verify_message$&. If you
28391 want this logged, you must set it up explicitly. For example:
28393 warn !verify = sender
28394 log_message = sender verify failed: $acl_verify_message
28398 At the end of each ACL there is an implicit unconditional &%deny%&.
28400 As you can see from the examples above, the conditions and modifiers are
28401 written one to a line, with the first one on the same line as the verb, and
28402 subsequent ones on following lines. If you have a very long condition, you can
28403 continue it onto several physical lines by the usual backslash continuation
28404 mechanism. It is conventional to align the conditions vertically.
28408 .section "ACL variables" "SECTaclvariables"
28409 .cindex "&ACL;" "variables"
28410 There are some special variables that can be set during ACL processing. They
28411 can be used to pass information between different ACLs, different invocations
28412 of the same ACL in the same SMTP connection, and between ACLs and the routers,
28413 transports, and filters that are used to deliver a message. The names of these
28414 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
28415 an underscore, but the remainder of the name can be any sequence of
28416 alphanumeric characters and underscores that you choose. There is no limit on
28417 the number of ACL variables. The two sets act as follows:
28419 The values of those variables whose names begin with &$acl_c$& persist
28420 throughout an SMTP connection. They are never reset. Thus, a value that is set
28421 while receiving one message is still available when receiving the next message
28422 on the same SMTP connection.
28424 The values of those variables whose names begin with &$acl_m$& persist only
28425 while a message is being received. They are reset afterwards. They are also
28426 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
28429 When a message is accepted, the current values of all the ACL variables are
28430 preserved with the message and are subsequently made available at delivery
28431 time. The ACL variables are set by a modifier called &%set%&. For example:
28433 accept hosts = whatever
28434 set acl_m4 = some value
28435 accept authenticated = *
28436 set acl_c_auth = yes
28438 &*Note*&: A leading dollar sign is not used when naming a variable that is to
28439 be set. If you want to set a variable without taking any action, you can use a
28440 &%warn%& verb without any other modifiers or conditions.
28442 .oindex &%strict_acl_vars%&
28443 What happens if a syntactically valid but undefined ACL variable is
28444 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
28445 false (the default), an empty string is substituted; if it is true, an
28446 error is generated.
28448 Versions of Exim before 4.64 have a limited set of numbered variables, but
28449 their names are compatible, so there is no problem with upgrading.
28452 .section "Condition and modifier processing" "SECTcondmodproc"
28453 .cindex "&ACL;" "conditions; processing"
28454 .cindex "&ACL;" "modifiers; processing"
28455 An exclamation mark preceding a condition negates its result. For example:
28457 deny domains = *.dom.example
28458 !verify = recipient
28460 causes the ACL to return &"deny"& if the recipient domain ends in
28461 &'dom.example'& and the recipient address cannot be verified. Sometimes
28462 negation can be used on the right-hand side of a condition. For example, these
28463 two statements are equivalent:
28465 deny hosts = !192.168.3.4
28466 deny !hosts = 192.168.3.4
28468 However, for many conditions (&%verify%& being a good example), only left-hand
28469 side negation of the whole condition is possible.
28471 The arguments of conditions and modifiers are expanded. A forced failure
28472 of an expansion causes a condition to be ignored, that is, it behaves as if the
28473 condition is true. Consider these two statements:
28475 accept senders = ${lookup{$host_name}lsearch\
28476 {/some/file}{$value}fail}
28477 accept senders = ${lookup{$host_name}lsearch\
28478 {/some/file}{$value}{}}
28480 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
28481 the returned list is searched, but if the lookup fails the behaviour is
28482 different in the two cases. The &%fail%& in the first statement causes the
28483 condition to be ignored, leaving no further conditions. The &%accept%& verb
28484 therefore succeeds. The second statement, however, generates an empty list when
28485 the lookup fails. No sender can match an empty list, so the condition fails,
28486 and therefore the &%accept%& also fails.
28488 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
28489 specify actions that are taken as the conditions for a statement are checked;
28490 others specify text for messages that are used when access is denied or a
28491 warning is generated. The &%control%& modifier affects the way an incoming
28492 message is handled.
28494 The positioning of the modifiers in an ACL statement is important, because the
28495 processing of a verb ceases as soon as its outcome is known. Only those
28496 modifiers that have already been encountered will take effect. For example,
28497 consider this use of the &%message%& modifier:
28499 require message = Can't verify sender
28501 message = Can't verify recipient
28503 message = This message cannot be used
28505 If sender verification fails, Exim knows that the result of the statement is
28506 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
28507 so its text is used as the error message. If sender verification succeeds, but
28508 recipient verification fails, the second message is used. If recipient
28509 verification succeeds, the third message becomes &"current"&, but is never used
28510 because there are no more conditions to cause failure.
28512 For the &%deny%& verb, on the other hand, it is always the last &%message%&
28513 modifier that is used, because all the conditions must be true for rejection to
28514 happen. Specifying more than one &%message%& modifier does not make sense, and
28515 the message can even be specified after all the conditions. For example:
28518 !senders = *@my.domain.example
28519 message = Invalid sender from client host
28521 The &"deny"& result does not happen until the end of the statement is reached,
28522 by which time Exim has set up the message.
28526 .section "ACL modifiers" "SECTACLmodi"
28527 .cindex "&ACL;" "modifiers; list of"
28528 The ACL modifiers are as follows:
28531 .vitem &*add_header*&&~=&~<&'text'&>
28532 This modifier specifies one or more header lines that are to be added to an
28533 incoming message, assuming, of course, that the message is ultimately
28534 accepted. For details, see section &<<SECTaddheadacl>>&.
28536 .vitem &*continue*&&~=&~<&'text'&>
28537 .cindex "&%continue%& ACL modifier"
28538 .cindex "database" "updating in ACL"
28539 This modifier does nothing of itself, and processing of the ACL always
28540 continues with the next condition or modifier. The value of &%continue%& is in
28541 the side effects of expanding its argument. Typically this could be used to
28542 update a database. It is really just a syntactic tidiness, to avoid having to
28543 write rather ugly lines like this:
28545 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
28547 Instead, all you need is
28549 &`continue = `&<&'some expansion'&>
28552 .vitem &*control*&&~=&~<&'text'&>
28553 .cindex "&%control%& ACL modifier"
28554 This modifier affects the subsequent processing of the SMTP connection or of an
28555 incoming message that is accepted. The effect of the first type of control
28556 lasts for the duration of the connection, whereas the effect of the second type
28557 lasts only until the current message has been received. The message-specific
28558 controls always apply to the whole message, not to individual recipients,
28559 even if the &%control%& modifier appears in a RCPT ACL.
28561 As there are now quite a few controls that can be applied, they are described
28562 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
28563 in several different ways. For example:
28565 . ==== As this is a nested list, any displays it contains must be indented
28566 . ==== as otherwise they are too far to the left. That comment applies only
28567 . ==== when xmlto and fop are used; formatting with sdop gets it right either
28571 It can be at the end of an &%accept%& statement:
28573 accept ...some conditions
28574 control = queue_only
28576 In this case, the control is applied when this statement yields &"accept"&, in
28577 other words, when the conditions are all true.
28580 It can be in the middle of an &%accept%& statement:
28582 accept ...some conditions...
28583 control = queue_only
28584 ...some more conditions...
28586 If the first set of conditions are true, the control is applied, even if the
28587 statement does not accept because one of the second set of conditions is false.
28588 In this case, some subsequent statement must yield &"accept"& for the control
28592 It can be used with &%warn%& to apply the control, leaving the
28593 decision about accepting or denying to a subsequent verb. For
28596 warn ...some conditions...
28600 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
28601 &%logwrite%&, so it does not add anything to the message and does not write a
28605 If you want to apply a control unconditionally, you can use it with a
28606 &%require%& verb. For example:
28608 require control = no_multiline_responses
28612 .vitem &*delay*&&~=&~<&'time'&>
28613 .cindex "&%delay%& ACL modifier"
28615 This modifier may appear in any ACL except notquit. It causes Exim to wait for
28616 the time interval before proceeding. However, when testing Exim using the
28617 &%-bh%& option, the delay is not actually imposed (an appropriate message is
28618 output instead). The time is given in the usual Exim notation, and the delay
28619 happens as soon as the modifier is processed. In an SMTP session, pending
28620 output is flushed before the delay is imposed.
28622 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
28625 deny ...some conditions...
28628 The delay happens if all the conditions are true, before the statement returns
28629 &"deny"&. Compare this with:
28632 ...some conditions...
28634 which waits for 30s before processing the conditions. The &%delay%& modifier
28635 can also be used with &%warn%& and together with &%control%&:
28637 warn ...some conditions...
28643 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
28644 responses to several commands are no longer buffered and sent in one packet (as
28645 they would normally be) because all output is flushed before imposing the
28646 delay. This optimization is disabled so that a number of small delays do not
28647 appear to the client as one large aggregated delay that might provoke an
28648 unwanted timeout. You can, however, disable output flushing for &%delay%& by
28649 using a &%control%& modifier to set &%no_delay_flush%&.
28653 .cindex "&%endpass%& ACL modifier"
28654 This modifier, which has no argument, is recognized only in &%accept%& and
28655 &%discard%& statements. It marks the boundary between the conditions whose
28656 failure causes control to pass to the next statement, and the conditions whose
28657 failure causes the ACL to return &"deny"&. This concept has proved to be
28658 confusing to some people, so the use of &%endpass%& is no longer recommended as
28659 &"best practice"&. See the description of &%accept%& above for more details.
28662 .vitem &*log_message*&&~=&~<&'text'&>
28663 .cindex "&%log_message%& ACL modifier"
28664 This modifier sets up a message that is used as part of the log message if the
28665 ACL denies access or a &%warn%& statement's conditions are true. For example:
28667 require log_message = wrong cipher suite $tls_in_cipher
28668 encrypted = DES-CBC3-SHA
28670 &%log_message%& is also used when recipients are discarded by &%discard%&. For
28673 &`discard `&<&'some conditions'&>
28674 &` log_message = Discarded $local_part@$domain because...`&
28676 When access is denied, &%log_message%& adds to any underlying error message
28677 that may exist because of a condition failure. For example, while verifying a
28678 recipient address, a &':fail:'& redirection might have already set up a
28681 The message may be defined before the conditions to which it applies, because
28682 the string expansion does not happen until Exim decides that access is to be
28683 denied. This means that any variables that are set by the condition are
28684 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
28685 variables are set after a DNS black list lookup succeeds. If the expansion of
28686 &%log_message%& fails, or if the result is an empty string, the modifier is
28689 .vindex "&$acl_verify_message$&"
28690 If you want to use a &%warn%& statement to log the result of an address
28691 verification, you can use &$acl_verify_message$& to include the verification
28694 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
28695 the start of the logged message. If the same warning log message is requested
28696 more than once while receiving a single email message, only one copy is
28697 actually logged. If you want to log multiple copies, use &%logwrite%& instead
28698 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
28699 is logged for a successful &%warn%& statement.
28701 If &%log_message%& is not present and there is no underlying error message (for
28702 example, from the failure of address verification), but &%message%& is present,
28703 the &%message%& text is used for logging rejections. However, if any text for
28704 logging contains newlines, only the first line is logged. In the absence of
28705 both &%log_message%& and &%message%&, a default built-in message is used for
28706 logging rejections.
28709 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
28710 .cindex "&%log_reject_target%& ACL modifier"
28711 .cindex "logging in ACL" "specifying which log"
28712 This modifier makes it possible to specify which logs are used for messages
28713 about ACL rejections. Its argument is a colon-separated list of words that can
28714 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
28715 may be empty, in which case a rejection is not logged at all. For example, this
28716 ACL fragment writes no logging information when access is denied:
28718 &`deny `&<&'some conditions'&>
28719 &` log_reject_target =`&
28721 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
28722 permanent and temporary rejections. Its effect lasts for the rest of the
28726 .vitem &*logwrite*&&~=&~<&'text'&>
28727 .cindex "&%logwrite%& ACL modifier"
28728 .cindex "logging in ACL" "immediate"
28729 This modifier writes a message to a log file as soon as it is encountered when
28730 processing an ACL. (Compare &%log_message%&, which, except in the case of
28731 &%warn%& and &%discard%&, is used only if the ACL statement denies
28732 access.) The &%logwrite%& modifier can be used to log special incidents in
28735 &`accept `&<&'some special conditions'&>
28736 &` control = freeze`&
28737 &` logwrite = froze message because ...`&
28739 By default, the message is written to the main log. However, it may begin
28740 with a colon, followed by a comma-separated list of log names, and then
28741 another colon, to specify exactly which logs are to be written. For
28744 logwrite = :main,reject: text for main and reject logs
28745 logwrite = :panic: text for panic log only
28749 .vitem &*message*&&~=&~<&'text'&>
28750 .cindex "&%message%& ACL modifier"
28751 This modifier sets up a text string that is expanded and used as a response
28752 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
28753 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
28754 there is some complication if &%endpass%& is involved; see the description of
28755 &%accept%& for details.)
28757 The expansion of the message happens at the time Exim decides that the ACL is
28758 to end, not at the time it processes &%message%&. If the expansion fails, or
28759 generates an empty string, the modifier is ignored. Here is an example where
28760 &%message%& must be specified first, because the ACL ends with a rejection if
28761 the &%hosts%& condition fails:
28763 require message = Host not recognized
28766 (Once a condition has failed, no further conditions or modifiers are
28769 .cindex "SMTP" "error codes"
28770 .oindex "&%smtp_banner%&
28771 For ACLs that are triggered by SMTP commands, the message is returned as part
28772 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
28773 is meaningful only for SMTP, as no message is returned when a non-SMTP message
28774 is accepted. In the case of the connect ACL, accepting with a message modifier
28775 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
28776 accept message may not contain more than one line (otherwise it will be
28777 truncated at the first newline and a panic logged), and it cannot affect the
28780 When SMTP is involved, the message may begin with an overriding response code,
28781 consisting of three digits optionally followed by an &"extended response code"&
28782 of the form &'n.n.n'&, each code being followed by a space. For example:
28784 deny message = 599 1.2.3 Host not welcome
28785 hosts = 192.168.34.0/24
28787 The first digit of the supplied response code must be the same as would be sent
28788 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
28789 access, but for the predata ACL, note that the default success code is 354, not
28792 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
28793 the message modifier cannot override the 221 response code.
28795 The text in a &%message%& modifier is literal; any quotes are taken as
28796 literals, but because the string is expanded, backslash escapes are processed
28797 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
28800 .vindex "&$acl_verify_message$&"
28801 For ACLs that are called by an &%acl =%& ACL condition, the message is
28802 stored in &$acl_verify_message$&, from which the calling ACL may use it.
28804 If &%message%& is used on a statement that verifies an address, the message
28805 specified overrides any message that is generated by the verification process.
28806 However, the original message is available in the variable
28807 &$acl_verify_message$&, so you can incorporate it into your message if you
28808 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
28809 routers to be passed back as part of the SMTP response, you should either not
28810 use a &%message%& modifier, or make use of &$acl_verify_message$&.
28812 For compatibility with previous releases of Exim, a &%message%& modifier that
28813 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
28814 modifier, but this usage is now deprecated. However, &%message%& acts only when
28815 all the conditions are true, wherever it appears in an ACL command, whereas
28816 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
28817 &%warn%& in an ACL that is not concerned with receiving a message, it has no
28821 .vitem &*queue*&&~=&~<&'text'&>
28822 This modifier specifies the use of a named queue for spool files
28824 It can only be used before the message is received (i.e. not in
28826 This could be used, for example, for known high-volume burst sources
28827 of traffic, or for quarantine of messages.
28828 Separate queue-runner processes will be needed for named queues.
28829 If the text after expansion is empty, the default queue is used.
28832 .vitem &*remove_header*&&~=&~<&'text'&>
28833 This modifier specifies one or more header names in a colon-separated list
28834 that are to be removed from an incoming message, assuming, of course, that
28835 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
28838 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
28839 .cindex "&%set%& ACL modifier"
28840 This modifier puts a value into one of the ACL variables (see section
28841 &<<SECTaclvariables>>&).
28844 .vitem &*udpsend*&&~=&~<&'parameters'&>
28845 This modifier sends a UDP packet, for purposes such as statistics
28846 collection or behaviour monitoring. The parameters are expanded, and
28847 the result of the expansion must be a colon-separated list consisting
28848 of a destination server, port number, and the packet contents. The
28849 server can be specified as a host name or IPv4 or IPv6 address. The
28850 separator can be changed with the usual angle bracket syntax. For
28851 example, you might want to collect information on which hosts connect
28854 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
28855 $tod_zulu $sender_host_address
28862 .section "Use of the control modifier" "SECTcontrols"
28863 .cindex "&%control%& ACL modifier"
28864 The &%control%& modifier supports the following settings:
28867 .vitem &*control&~=&~allow_auth_unadvertised*&
28868 This modifier allows a client host to use the SMTP AUTH command even when it
28869 has not been advertised in response to EHLO. Furthermore, because there are
28870 apparently some really broken clients that do this, Exim will accept AUTH after
28871 HELO (rather than EHLO) when this control is set. It should be used only if you
28872 really need it, and you should limit its use to those broken clients that do
28873 not work without it. For example:
28875 warn hosts = 192.168.34.25
28876 control = allow_auth_unadvertised
28878 Normally, when an Exim server receives an AUTH command, it checks the name of
28879 the authentication mechanism that is given in the command to ensure that it
28880 matches an advertised mechanism. When this control is set, the check that a
28881 mechanism has been advertised is bypassed. Any configured mechanism can be used
28882 by the client. This control is permitted only in the connection and HELO ACLs.
28885 .vitem &*control&~=&~caseful_local_part*& &&&
28886 &*control&~=&~caselower_local_part*&
28887 .cindex "&ACL;" "case of local part in"
28888 .cindex "case of local parts"
28889 .vindex "&$local_part$&"
28890 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
28891 (that is, during RCPT processing). By default, the contents of &$local_part$&
28892 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
28893 any uppercase letters in the original local part are restored in &$local_part$&
28894 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
28897 These controls affect only the current recipient. Moreover, they apply only to
28898 local part handling that takes place directly in the ACL (for example, as a key
28899 in lookups). If a test to verify the recipient is obeyed, the case-related
28900 handling of the local part during the verification is controlled by the router
28901 configuration (see the &%caseful_local_part%& generic router option).
28903 This facility could be used, for example, to add a spam score to local parts
28904 containing upper case letters. For example, using &$acl_m4$& to accumulate the
28907 warn control = caseful_local_part
28908 set acl_m4 = ${eval:\
28910 ${if match{$local_part}{[A-Z]}{1}{0}}\
28912 control = caselower_local_part
28914 Notice that we put back the lower cased version afterwards, assuming that
28915 is what is wanted for subsequent tests.
28918 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
28919 .cindex "&ACL;" "cutthrough routing"
28920 .cindex "cutthrough" "requesting"
28921 This option requests delivery be attempted while the item is being received.
28923 The option is usable in the RCPT ACL.
28924 If enabled for a message received via smtp and routed to an smtp transport,
28925 and only one transport, interface, destination host and port combination
28926 is used for all recipients of the message,
28927 then the delivery connection is made while the receiving connection is open
28928 and data is copied from one to the other.
28930 An attempt to set this option for any recipient but the first
28931 for a mail will be quietly ignored.
28932 If a recipient-verify callout
28934 connection is subsequently
28935 requested in the same ACL it is held open and used for
28936 any subsequent recipients and the data,
28937 otherwise one is made after the initial RCPT ACL completes.
28939 Note that routers are used in verify mode,
28940 and cannot depend on content of received headers.
28941 Note also that headers cannot be
28942 modified by any of the post-data ACLs (DATA, MIME and DKIM).
28943 Headers may be modified by routers (subject to the above) and transports.
28945 All the usual ACLs are called; if one results in the message being
28946 rejected, all effort spent in delivery (including the costs on
28947 the ultimate destination) will be wasted.
28948 Note that in the case of data-time ACLs this includes the entire
28951 Cutthrough delivery is not supported via transport-filters or when DKIM signing
28952 of outgoing messages is done, because it sends data to the ultimate destination
28953 before the entire message has been received from the source.
28954 It is not supported for messages received with the SMTP PRDR
28958 Should the ultimate destination system positively accept or reject the mail,
28959 a corresponding indication is given to the source system and nothing is queued.
28960 If the item is successfully delivered in cutthrough mode
28961 the delivery log lines are tagged with ">>" rather than "=>" and appear
28962 before the acceptance "<=" line.
28964 If there is a temporary error the item is queued for later delivery in the
28966 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
28967 to the control; the default value is &"spool"& and the alternate value
28968 &"pass"& copies an SMTP defer response from the target back to the initiator
28969 and does not queue the message.
28970 Note that this is independent of any recipient verify conditions in the ACL.
28972 Delivery in this mode avoids the generation of a bounce mail to a
28974 sender when the destination system is doing content-scan based rejection.
28977 .vitem &*control&~=&~debug/*&<&'options'&>
28978 .cindex "&ACL;" "enabling debug logging"
28979 .cindex "debugging" "enabling from an ACL"
28980 This control turns on debug logging, almost as though Exim had been invoked
28981 with &`-d`&, with the output going to a new logfile, by default called
28982 &'debuglog'&. The filename can be adjusted with the &'tag'& option, which
28983 may access any variables already defined. The logging may be adjusted with
28984 the &'opts'& option, which takes the same values as the &`-d`& command-line
28986 Logging may be stopped, and the file removed, with the &'kill'& option.
28987 Some examples (which depend on variables that don't exist in all
28991 control = debug/tag=.$sender_host_address
28992 control = debug/opts=+expand+acl
28993 control = debug/tag=.$message_exim_id/opts=+expand
28994 control = debug/kill
28998 .vitem &*control&~=&~dkim_disable_verify*&
28999 .cindex "disable DKIM verify"
29000 .cindex "DKIM" "disable verify"
29001 This control turns off DKIM verification processing entirely. For details on
29002 the operation and configuration of DKIM, see chapter &<<CHAPdkim>>&.
29005 .vitem &*control&~=&~dscp/*&<&'value'&>
29006 .cindex "&ACL;" "setting DSCP value"
29007 .cindex "DSCP" "inbound"
29008 This option causes the DSCP value associated with the socket for the inbound
29009 connection to be adjusted to a given value, given as one of a number of fixed
29010 strings or to numeric value.
29011 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
29012 Common values include &`throughput`&, &`mincost`&, and on newer systems
29013 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
29015 The outbound packets from Exim will be marked with this value in the header
29016 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
29017 that these values will have any effect, not be stripped by networking
29018 equipment, or do much of anything without cooperation with your Network
29019 Engineer and those of all network operators between the source and destination.
29022 .vitem &*control&~=&~enforce_sync*& &&&
29023 &*control&~=&~no_enforce_sync*&
29024 .cindex "SMTP" "synchronization checking"
29025 .cindex "synchronization checking in SMTP"
29026 These controls make it possible to be selective about when SMTP synchronization
29027 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
29028 state of the switch (it is true by default). See the description of this option
29029 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
29031 The effect of these two controls lasts for the remainder of the SMTP
29032 connection. They can appear in any ACL except the one for the non-SMTP
29033 messages. The most straightforward place to put them is in the ACL defined by
29034 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
29035 before the first synchronization check. The expected use is to turn off the
29036 synchronization checks for badly-behaved hosts that you nevertheless need to
29040 .vitem &*control&~=&~fakedefer/*&<&'message'&>
29041 .cindex "fake defer"
29042 .cindex "defer, fake"
29043 This control works in exactly the same way as &%fakereject%& (described below)
29044 except that it causes an SMTP 450 response after the message data instead of a
29045 550 response. You must take care when using &%fakedefer%& because it causes the
29046 messages to be duplicated when the sender retries. Therefore, you should not
29047 use &%fakedefer%& if the message is to be delivered normally.
29049 .vitem &*control&~=&~fakereject/*&<&'message'&>
29050 .cindex "fake rejection"
29051 .cindex "rejection, fake"
29052 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
29053 words, only when an SMTP message is being received. If Exim accepts the
29054 message, instead the final 250 response, a 550 rejection message is sent.
29055 However, Exim proceeds to deliver the message as normal. The control applies
29056 only to the current message, not to any subsequent ones that may be received in
29057 the same SMTP connection.
29059 The text for the 550 response is taken from the &%control%& modifier. If no
29060 message is supplied, the following is used:
29062 550-Your message has been rejected but is being
29063 550-kept for evaluation.
29064 550-If it was a legitimate message, it may still be
29065 550 delivered to the target recipient(s).
29067 This facility should be used with extreme caution.
29069 .vitem &*control&~=&~freeze*&
29070 .cindex "frozen messages" "forcing in ACL"
29071 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29072 other words, only when a message is being received. If the message is accepted,
29073 it is placed on Exim's queue and frozen. The control applies only to the
29074 current message, not to any subsequent ones that may be received in the same
29077 This modifier can optionally be followed by &`/no_tell`&. If the global option
29078 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
29079 is told about the freezing), provided all the &*control=freeze*& modifiers that
29080 are obeyed for the current message have the &`/no_tell`& option.
29082 .vitem &*control&~=&~no_delay_flush*&
29083 .cindex "SMTP" "output flushing, disabling for delay"
29084 Exim normally flushes SMTP output before implementing a delay in an ACL, to
29085 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29086 use. This control, as long as it is encountered before the &%delay%& modifier,
29087 disables such output flushing.
29089 .vitem &*control&~=&~no_callout_flush*&
29090 .cindex "SMTP" "output flushing, disabling for callout"
29091 Exim normally flushes SMTP output before performing a callout in an ACL, to
29092 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29093 use. This control, as long as it is encountered before the &%verify%& condition
29094 that causes the callout, disables such output flushing.
29096 .vitem &*control&~=&~no_mbox_unspool*&
29097 This control is available when Exim is compiled with the content scanning
29098 extension. Content scanning may require a copy of the current message, or parts
29099 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
29100 or spam scanner. Normally, such copies are deleted when they are no longer
29101 needed. If this control is set, the copies are not deleted. The control applies
29102 only to the current message, not to any subsequent ones that may be received in
29103 the same SMTP connection. It is provided for debugging purposes and is unlikely
29104 to be useful in production.
29106 .vitem &*control&~=&~no_multiline_responses*&
29107 .cindex "multiline responses, suppressing"
29108 This control is permitted for any ACL except the one for non-SMTP messages.
29109 It seems that there are broken clients in use that cannot handle multiline
29110 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
29112 If this control is set, multiline SMTP responses from ACL rejections are
29113 suppressed. One way of doing this would have been to put out these responses as
29114 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
29115 (&"use multiline responses for more"& it says &-- ha!), and some of the
29116 responses might get close to that. So this facility, which is after all only a
29117 sop to broken clients, is implemented by doing two very easy things:
29120 Extra information that is normally output as part of a rejection caused by
29121 sender verification failure is omitted. Only the final line (typically &"sender
29122 verification failed"&) is sent.
29124 If a &%message%& modifier supplies a multiline response, only the first
29128 The setting of the switch can, of course, be made conditional on the
29129 calling host. Its effect lasts until the end of the SMTP connection.
29131 .vitem &*control&~=&~no_pipelining*&
29132 .cindex "PIPELINING" "suppressing advertising"
29133 This control turns off the advertising of the PIPELINING extension to SMTP in
29134 the current session. To be useful, it must be obeyed before Exim sends its
29135 response to an EHLO command. Therefore, it should normally appear in an ACL
29136 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
29137 &%pipelining_advertise_hosts%&.
29139 .vitem &*control&~=&~queue_only*&
29140 .oindex "&%queue_only%&"
29141 .cindex "queueing incoming messages"
29142 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29143 other words, only when a message is being received. If the message is accepted,
29144 it is placed on Exim's queue and left there for delivery by a subsequent queue
29145 runner. No immediate delivery process is started. In other words, it has the
29146 effect as the &%queue_only%& global option. However, the control applies only
29147 to the current message, not to any subsequent ones that may be received in the
29148 same SMTP connection.
29150 .vitem &*control&~=&~submission/*&<&'options'&>
29151 .cindex "message" "submission"
29152 .cindex "submission mode"
29153 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
29154 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
29155 the current message is a submission from a local MUA. In this case, Exim
29156 operates in &"submission mode"&, and applies certain fixups to the message if
29157 necessary. For example, it adds a &'Date:'& header line if one is not present.
29158 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
29159 late (the message has already been created).
29161 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
29162 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
29163 submission mode; the available options for this control are described there.
29164 The control applies only to the current message, not to any subsequent ones
29165 that may be received in the same SMTP connection.
29167 .vitem &*control&~=&~suppress_local_fixups*&
29168 .cindex "submission fixups, suppressing"
29169 This control applies to locally submitted (non TCP/IP) messages, and is the
29170 complement of &`control = submission`&. It disables the fixups that are
29171 normally applied to locally-submitted messages. Specifically:
29174 Any &'Sender:'& header line is left alone (in this respect, it is a
29175 dynamic version of &%local_sender_retain%&).
29177 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
29179 There is no check that &'From:'& corresponds to the actual sender.
29182 This control may be useful when a remotely-originated message is accepted,
29183 passed to some scanning program, and then re-submitted for delivery. It can be
29184 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29185 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
29188 &*Note:*& This control applies only to the current message, not to any others
29189 that are being submitted at the same time using &%-bs%& or &%-bS%&.
29191 .vitem &*control&~=&~utf8_downconvert*&
29192 This control enables conversion of UTF-8 in message addresses
29194 For details see section &<<SECTi18nMTA>>&.
29198 .section "Summary of message fixup control" "SECTsummesfix"
29199 All four possibilities for message fixups can be specified:
29202 Locally submitted, fixups applied: the default.
29204 Locally submitted, no fixups applied: use
29205 &`control = suppress_local_fixups`&.
29207 Remotely submitted, no fixups applied: the default.
29209 Remotely submitted, fixups applied: use &`control = submission`&.
29214 .section "Adding header lines in ACLs" "SECTaddheadacl"
29215 .cindex "header lines" "adding in an ACL"
29216 .cindex "header lines" "position of added lines"
29217 .cindex "&%add_header%& ACL modifier"
29218 The &%add_header%& modifier can be used to add one or more extra header lines
29219 to an incoming message, as in this example:
29221 warn dnslists = sbl.spamhaus.org : \
29222 dialup.mail-abuse.org
29223 add_header = X-blacklisted-at: $dnslist_domain
29225 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29226 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29227 receiving a message). The message must ultimately be accepted for
29228 &%add_header%& to have any significant effect. You can use &%add_header%& with
29229 any ACL verb, including &%deny%& (though this is potentially useful only in a
29232 Headers will not be added to the message if the modifier is used in
29233 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29235 Leading and trailing newlines are removed from
29236 the data for the &%add_header%& modifier; if it then
29237 contains one or more newlines that
29238 are not followed by a space or a tab, it is assumed to contain multiple header
29239 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
29240 front of any line that is not a valid header line.
29242 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29243 They are added to the message before processing the DATA and MIME ACLs.
29244 However, if an identical header line is requested more than once, only one copy
29245 is actually added to the message. Further header lines may be accumulated
29246 during the DATA and MIME ACLs, after which they are added to the message, again
29247 with duplicates suppressed. Thus, it is possible to add two identical header
29248 lines to an SMTP message, but only if one is added before DATA and one after.
29249 In the case of non-SMTP messages, new headers are accumulated during the
29250 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
29251 message is rejected after DATA or by the non-SMTP ACL, all added header lines
29252 are included in the entry that is written to the reject log.
29254 .cindex "header lines" "added; visibility of"
29255 Header lines are not visible in string expansions
29257 until they are added to the
29258 message. It follows that header lines defined in the MAIL, RCPT, and predata
29259 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
29260 header lines that are added by the DATA or MIME ACLs are not visible in those
29261 ACLs. Because of this restriction, you cannot use header lines as a way of
29262 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
29263 this, you can use ACL variables, as described in section
29264 &<<SECTaclvariables>>&.
29266 The list of headers yet to be added is given by the &%$headers_added%& variable.
29268 The &%add_header%& modifier acts immediately as it is encountered during the
29269 processing of an ACL. Notice the difference between these two cases:
29271 &`accept add_header = ADDED: some text`&
29272 &` `&<&'some condition'&>
29274 &`accept `&<&'some condition'&>
29275 &` add_header = ADDED: some text`&
29277 In the first case, the header line is always added, whether or not the
29278 condition is true. In the second case, the header line is added only if the
29279 condition is true. Multiple occurrences of &%add_header%& may occur in the same
29280 ACL statement. All those that are encountered before a condition fails are
29283 .cindex "&%warn%& ACL verb"
29284 For compatibility with previous versions of Exim, a &%message%& modifier for a
29285 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
29286 effect only if all the conditions are true, even if it appears before some of
29287 them. Furthermore, only the last occurrence of &%message%& is honoured. This
29288 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
29289 are present on a &%warn%& verb, both are processed according to their
29292 By default, new header lines are added to a message at the end of the existing
29293 header lines. However, you can specify that any particular header line should
29294 be added right at the start (before all the &'Received:'& lines), immediately
29295 after the first block of &'Received:'& lines, or immediately before any line
29296 that is not a &'Received:'& or &'Resent-something:'& header.
29298 This is done by specifying &":at_start:"&, &":after_received:"&, or
29299 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
29300 header line, respectively. (Header text cannot start with a colon, as there has
29301 to be a header name first.) For example:
29303 warn add_header = \
29304 :after_received:X-My-Header: something or other...
29306 If more than one header line is supplied in a single &%add_header%& modifier,
29307 each one is treated independently and can therefore be placed differently. If
29308 you add more than one line at the start, or after the Received: block, they end
29309 up in reverse order.
29311 &*Warning*&: This facility currently applies only to header lines that are
29312 added in an ACL. It does NOT work for header lines that are added in a
29313 system filter or in a router or transport.
29317 .section "Removing header lines in ACLs" "SECTremoveheadacl"
29318 .cindex "header lines" "removing in an ACL"
29319 .cindex "header lines" "position of removed lines"
29320 .cindex "&%remove_header%& ACL modifier"
29321 The &%remove_header%& modifier can be used to remove one or more header lines
29322 from an incoming message, as in this example:
29324 warn message = Remove internal headers
29325 remove_header = x-route-mail1 : x-route-mail2
29327 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29328 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29329 receiving a message). The message must ultimately be accepted for
29330 &%remove_header%& to have any significant effect. You can use &%remove_header%&
29331 with any ACL verb, including &%deny%&, though this is really not useful for
29332 any verb that doesn't result in a delivered message.
29334 Headers will not be removed from the message if the modifier is used in
29335 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29337 More than one header can be removed at the same time by using a colon separated
29338 list of header names. The header matching is case insensitive. Wildcards are
29339 not permitted, nor is list expansion performed, so you cannot use hostlists to
29340 create a list of headers, however both connection and message variable expansion
29341 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
29343 warn hosts = +internal_hosts
29344 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
29345 warn message = Remove internal headers
29346 remove_header = $acl_c_ihdrs
29348 Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29349 They are removed from the message before processing the DATA and MIME ACLs.
29350 There is no harm in attempting to remove the same header twice nor is removing
29351 a non-existent header. Further header lines to be removed may be accumulated
29352 during the DATA and MIME ACLs, after which they are removed from the message,
29353 if present. In the case of non-SMTP messages, headers to be removed are
29354 accumulated during the non-SMTP ACLs, and are removed from the message after
29355 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
29356 ACL, there really is no effect because there is no logging of what headers
29357 would have been removed.
29359 .cindex "header lines" "removed; visibility of"
29360 Header lines are not visible in string expansions until the DATA phase when it
29361 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
29362 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
29363 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
29364 this restriction, you cannot use header lines as a way of controlling data
29365 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
29366 you should instead use ACL variables, as described in section
29367 &<<SECTaclvariables>>&.
29369 The &%remove_header%& modifier acts immediately as it is encountered during the
29370 processing of an ACL. Notice the difference between these two cases:
29372 &`accept remove_header = X-Internal`&
29373 &` `&<&'some condition'&>
29375 &`accept `&<&'some condition'&>
29376 &` remove_header = X-Internal`&
29378 In the first case, the header line is always removed, whether or not the
29379 condition is true. In the second case, the header line is removed only if the
29380 condition is true. Multiple occurrences of &%remove_header%& may occur in the
29381 same ACL statement. All those that are encountered before a condition fails
29384 &*Warning*&: This facility currently applies only to header lines that are
29385 present during ACL processing. It does NOT remove header lines that are added
29386 in a system filter or in a router or transport.
29391 .section "ACL conditions" "SECTaclconditions"
29392 .cindex "&ACL;" "conditions; list of"
29393 Some of the conditions listed in this section are available only when Exim is
29394 compiled with the content-scanning extension. They are included here briefly
29395 for completeness. More detailed descriptions can be found in the discussion on
29396 content scanning in chapter &<<CHAPexiscan>>&.
29398 Not all conditions are relevant in all circumstances. For example, testing
29399 senders and recipients does not make sense in an ACL that is being run as the
29400 result of the arrival of an ETRN command, and checks on message headers can be
29401 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
29402 can use the same condition (with different parameters) more than once in the
29403 same ACL statement. This provides a way of specifying an &"and"& conjunction.
29404 The conditions are as follows:
29408 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
29409 .cindex "&ACL;" "nested"
29410 .cindex "&ACL;" "indirect"
29411 .cindex "&ACL;" "arguments"
29412 .cindex "&%acl%& ACL condition"
29413 The possible values of the argument are the same as for the
29414 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
29415 &"accept"& the condition is true; if it returns &"deny"& the condition is
29416 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
29417 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
29418 condition false. This means that further processing of the &%warn%& verb
29419 ceases, but processing of the ACL continues.
29421 If the argument is a named ACL, up to nine space-separated optional values
29422 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
29423 and $acl_narg is set to the count of values.
29424 Previous values of these variables are restored after the call returns.
29425 The name and values are expanded separately.
29426 Note that spaces in complex expansions which are used as arguments
29427 will act as argument separators.
29429 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
29430 the connection is dropped. If it returns &"discard"&, the verb must be
29431 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
29432 conditions are tested.
29434 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
29435 loops. This condition allows you to use different ACLs in different
29436 circumstances. For example, different ACLs can be used to handle RCPT commands
29437 for different local users or different local domains.
29439 .vitem &*authenticated&~=&~*&<&'string&~list'&>
29440 .cindex "&%authenticated%& ACL condition"
29441 .cindex "authentication" "ACL checking"
29442 .cindex "&ACL;" "testing for authentication"
29443 If the SMTP connection is not authenticated, the condition is false. Otherwise,
29444 the name of the authenticator is tested against the list. To test for
29445 authentication by any authenticator, you can set
29450 .vitem &*condition&~=&~*&<&'string'&>
29451 .cindex "&%condition%& ACL condition"
29452 .cindex "customizing" "ACL condition"
29453 .cindex "&ACL;" "customized test"
29454 .cindex "&ACL;" "testing, customized"
29455 This feature allows you to make up custom conditions. If the result of
29456 expanding the string is an empty string, the number zero, or one of the strings
29457 &"no"& or &"false"&, the condition is false. If the result is any non-zero
29458 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
29459 any other value, some error is assumed to have occurred, and the ACL returns
29460 &"defer"&. However, if the expansion is forced to fail, the condition is
29461 ignored. The effect is to treat it as true, whether it is positive or
29464 .vitem &*decode&~=&~*&<&'location'&>
29465 .cindex "&%decode%& ACL condition"
29466 This condition is available only when Exim is compiled with the
29467 content-scanning extension, and it is allowed only in the ACL defined by
29468 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
29469 If all goes well, the condition is true. It is false only if there are
29470 problems such as a syntax error or a memory shortage. For more details, see
29471 chapter &<<CHAPexiscan>>&.
29473 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
29474 .cindex "&%dnslists%& ACL condition"
29475 .cindex "DNS list" "in ACL"
29476 .cindex "black list (DNS)"
29477 .cindex "&ACL;" "testing a DNS list"
29478 This condition checks for entries in DNS black lists. These are also known as
29479 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
29480 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
29481 different variants of this condition to describe briefly here. See sections
29482 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
29484 .vitem &*domains&~=&~*&<&'domain&~list'&>
29485 .cindex "&%domains%& ACL condition"
29486 .cindex "domain" "ACL checking"
29487 .cindex "&ACL;" "testing a recipient domain"
29488 .vindex "&$domain_data$&"
29489 This condition is relevant only after a RCPT command. It checks that the domain
29490 of the recipient address is in the domain list. If percent-hack processing is
29491 enabled, it is done before this test is done. If the check succeeds with a
29492 lookup, the result of the lookup is placed in &$domain_data$& until the next
29495 &*Note carefully*& (because many people seem to fall foul of this): you cannot
29496 use &%domains%& in a DATA ACL.
29499 .vitem &*encrypted&~=&~*&<&'string&~list'&>
29500 .cindex "&%encrypted%& ACL condition"
29501 .cindex "encryption" "checking in an ACL"
29502 .cindex "&ACL;" "testing for encryption"
29503 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
29504 name of the cipher suite in use is tested against the list. To test for
29505 encryption without testing for any specific cipher suite(s), set
29511 .vitem &*hosts&~=&~*&<&'host&~list'&>
29512 .cindex "&%hosts%& ACL condition"
29513 .cindex "host" "ACL checking"
29514 .cindex "&ACL;" "testing the client host"
29515 This condition tests that the calling host matches the host list. If you have
29516 name lookups or wildcarded host names and IP addresses in the same host list,
29517 you should normally put the IP addresses first. For example, you could have:
29519 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
29521 The lookup in this example uses the host name for its key. This is implied by
29522 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
29523 and it wouldn't matter which way round you had these two items.)
29525 The reason for the problem with host names lies in the left-to-right way that
29526 Exim processes lists. It can test IP addresses without doing any DNS lookups,
29527 but when it reaches an item that requires a host name, it fails if it cannot
29528 find a host name to compare with the pattern. If the above list is given in the
29529 opposite order, the &%accept%& statement fails for a host whose name cannot be
29530 found, even if its IP address is 10.9.8.7.
29532 If you really do want to do the name check first, and still recognize the IP
29533 address even if the name lookup fails, you can rewrite the ACL like this:
29535 accept hosts = dbm;/etc/friendly/hosts
29536 accept hosts = 10.9.8.7
29538 The default action on failing to find the host name is to assume that the host
29539 is not in the list, so the first &%accept%& statement fails. The second
29540 statement can then check the IP address.
29542 .vindex "&$host_data$&"
29543 If a &%hosts%& condition is satisfied by means of a lookup, the result
29544 of the lookup is made available in the &$host_data$& variable. This
29545 allows you, for example, to set up a statement like this:
29547 deny hosts = net-lsearch;/some/file
29548 message = $host_data
29550 which gives a custom error message for each denied host.
29552 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
29553 .cindex "&%local_parts%& ACL condition"
29554 .cindex "local part" "ACL checking"
29555 .cindex "&ACL;" "testing a local part"
29556 .vindex "&$local_part_data$&"
29557 This condition is relevant only after a RCPT command. It checks that the local
29558 part of the recipient address is in the list. If percent-hack processing is
29559 enabled, it is done before this test. If the check succeeds with a lookup, the
29560 result of the lookup is placed in &$local_part_data$&, which remains set until
29561 the next &%local_parts%& test.
29563 .vitem &*malware&~=&~*&<&'option'&>
29564 .cindex "&%malware%& ACL condition"
29565 .cindex "&ACL;" "virus scanning"
29566 .cindex "&ACL;" "scanning for viruses"
29567 This condition is available only when Exim is compiled with the
29568 content-scanning extension. It causes the incoming message to be scanned for
29569 viruses. For details, see chapter &<<CHAPexiscan>>&.
29571 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29572 .cindex "&%mime_regex%& ACL condition"
29573 .cindex "&ACL;" "testing by regex matching"
29574 This condition is available only when Exim is compiled with the
29575 content-scanning extension, and it is allowed only in the ACL defined by
29576 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
29577 with any of the regular expressions. For details, see chapter
29580 .vitem &*ratelimit&~=&~*&<&'parameters'&>
29581 .cindex "rate limiting"
29582 This condition can be used to limit the rate at which a user or host submits
29583 messages. Details are given in section &<<SECTratelimiting>>&.
29585 .vitem &*recipients&~=&~*&<&'address&~list'&>
29586 .cindex "&%recipients%& ACL condition"
29587 .cindex "recipient" "ACL checking"
29588 .cindex "&ACL;" "testing a recipient"
29589 This condition is relevant only after a RCPT command. It checks the entire
29590 recipient address against a list of recipients.
29592 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
29593 .cindex "&%regex%& ACL condition"
29594 .cindex "&ACL;" "testing by regex matching"
29595 This condition is available only when Exim is compiled with the
29596 content-scanning extension, and is available only in the DATA, MIME, and
29597 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
29598 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
29600 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
29601 .cindex "&%sender_domains%& ACL condition"
29602 .cindex "sender" "ACL checking"
29603 .cindex "&ACL;" "testing a sender domain"
29604 .vindex "&$domain$&"
29605 .vindex "&$sender_address_domain$&"
29606 This condition tests the domain of the sender of the message against the given
29607 domain list. &*Note*&: The domain of the sender address is in
29608 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
29609 of this condition. This is an exception to the general rule for testing domain
29610 lists. It is done this way so that, if this condition is used in an ACL for a
29611 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
29612 influence the sender checking.
29614 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29615 relaying, because sender addresses are easily, and commonly, forged.
29617 .vitem &*senders&~=&~*&<&'address&~list'&>
29618 .cindex "&%senders%& ACL condition"
29619 .cindex "sender" "ACL checking"
29620 .cindex "&ACL;" "testing a sender"
29621 This condition tests the sender of the message against the given list. To test
29622 for a bounce message, which has an empty sender, set
29626 &*Warning*&: It is a bad idea to use this condition on its own as a control on
29627 relaying, because sender addresses are easily, and commonly, forged.
29629 .vitem &*spam&~=&~*&<&'username'&>
29630 .cindex "&%spam%& ACL condition"
29631 .cindex "&ACL;" "scanning for spam"
29632 This condition is available only when Exim is compiled with the
29633 content-scanning extension. It causes the incoming message to be scanned by
29634 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
29636 .vitem &*verify&~=&~certificate*&
29637 .cindex "&%verify%& ACL condition"
29638 .cindex "TLS" "client certificate verification"
29639 .cindex "certificate" "verification of client"
29640 .cindex "&ACL;" "certificate verification"
29641 .cindex "&ACL;" "testing a TLS certificate"
29642 This condition is true in an SMTP session if the session is encrypted, and a
29643 certificate was received from the client, and the certificate was verified. The
29644 server requests a certificate only if the client matches &%tls_verify_hosts%&
29645 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
29647 .vitem &*verify&~=&~csa*&
29648 .cindex "CSA verification"
29649 This condition checks whether the sending host (the client) is authorized to
29650 send email. Details of how this works are given in section
29651 &<<SECTverifyCSA>>&.
29653 .vitem &*verify&~=&~header_names_ascii*&
29654 .cindex "&%verify%& ACL condition"
29655 .cindex "&ACL;" "verifying header names only ASCII"
29656 .cindex "header lines" "verifying header names only ASCII"
29657 .cindex "verifying" "header names only ASCII"
29658 This condition is relevant only in an ACL that is run after a message has been
29659 received, that is, in an ACL specified by &%acl_smtp_data%& or
29660 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
29661 there are no non-ASCII characters, also excluding control characters. The
29662 allowable characters are decimal ASCII values 33 through 126.
29664 Exim itself will handle headers with non-ASCII characters, but it can cause
29665 problems for downstream applications, so this option will allow their
29666 detection and rejection in the DATA ACL's.
29668 .vitem &*verify&~=&~header_sender/*&<&'options'&>
29669 .cindex "&%verify%& ACL condition"
29670 .cindex "&ACL;" "verifying sender in the header"
29671 .cindex "header lines" "verifying the sender in"
29672 .cindex "sender" "verifying in header"
29673 .cindex "verifying" "sender in header"
29674 This condition is relevant only in an ACL that is run after a message has been
29675 received, that is, in an ACL specified by &%acl_smtp_data%& or
29676 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
29677 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
29678 is loosely thought of as a &"sender"& address (hence the name of the test).
29679 However, an address that appears in one of these headers need not be an address
29680 that accepts bounce messages; only sender addresses in envelopes are required
29681 to accept bounces. Therefore, if you use the callout option on this check, you
29682 might want to arrange for a non-empty address in the MAIL command.
29684 Details of address verification and the options are given later, starting at
29685 section &<<SECTaddressverification>>& (callouts are described in section
29686 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
29687 condition to restrict it to bounce messages only:
29690 message = A valid sender header is required for bounces
29691 !verify = header_sender
29694 .vitem &*verify&~=&~header_syntax*&
29695 .cindex "&%verify%& ACL condition"
29696 .cindex "&ACL;" "verifying header syntax"
29697 .cindex "header lines" "verifying syntax"
29698 .cindex "verifying" "header syntax"
29699 This condition is relevant only in an ACL that is run after a message has been
29700 received, that is, in an ACL specified by &%acl_smtp_data%& or
29701 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
29702 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
29703 and &'Bcc:'&), returning true if there are no problems.
29704 Unqualified addresses (local parts without domains) are
29705 permitted only in locally generated messages and from hosts that match
29706 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
29709 Note that this condition is a syntax check only. However, a common spamming
29710 ploy used to be to send syntactically invalid headers such as
29714 and this condition can be used to reject such messages, though they are not as
29715 common as they used to be.
29717 .vitem &*verify&~=&~helo*&
29718 .cindex "&%verify%& ACL condition"
29719 .cindex "&ACL;" "verifying HELO/EHLO"
29720 .cindex "HELO" "verifying"
29721 .cindex "EHLO" "verifying"
29722 .cindex "verifying" "EHLO"
29723 .cindex "verifying" "HELO"
29724 This condition is true if a HELO or EHLO command has been received from the
29725 client host, and its contents have been verified. If there has been no previous
29726 attempt to verify the HELO/EHLO contents, it is carried out when this
29727 condition is encountered. See the description of the &%helo_verify_hosts%& and
29728 &%helo_try_verify_hosts%& options for details of how to request verification
29729 independently of this condition.
29731 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
29732 option), this condition is always true.
29735 .vitem &*verify&~=&~not_blind*&
29736 .cindex "verifying" "not blind"
29737 .cindex "bcc recipients, verifying none"
29738 This condition checks that there are no blind (bcc) recipients in the message.
29739 Every envelope recipient must appear either in a &'To:'& header line or in a
29740 &'Cc:'& header line for this condition to be true. Local parts are checked
29741 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
29742 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
29743 used only in a DATA or non-SMTP ACL.
29745 There are, of course, many legitimate messages that make use of blind (bcc)
29746 recipients. This check should not be used on its own for blocking messages.
29749 .vitem &*verify&~=&~recipient/*&<&'options'&>
29750 .cindex "&%verify%& ACL condition"
29751 .cindex "&ACL;" "verifying recipient"
29752 .cindex "recipient" "verifying"
29753 .cindex "verifying" "recipient"
29754 .vindex "&$address_data$&"
29755 This condition is relevant only after a RCPT command. It verifies the current
29756 recipient. Details of address verification are given later, starting at section
29757 &<<SECTaddressverification>>&. After a recipient has been verified, the value
29758 of &$address_data$& is the last value that was set while routing the address.
29759 This applies even if the verification fails. When an address that is being
29760 verified is redirected to a single address, verification continues with the new
29761 address, and in that case, the subsequent value of &$address_data$& is the
29762 value for the child address.
29764 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
29765 .cindex "&%verify%& ACL condition"
29766 .cindex "&ACL;" "verifying host reverse lookup"
29767 .cindex "host" "verifying reverse lookup"
29768 This condition ensures that a verified host name has been looked up from the IP
29769 address of the client host. (This may have happened already if the host name
29770 was needed for checking a host list, or if the host matched &%host_lookup%&.)
29771 Verification ensures that the host name obtained from a reverse DNS lookup, or
29772 one of its aliases, does, when it is itself looked up in the DNS, yield the
29773 original IP address.
29775 There is one possible option, &`defer_ok`&. If this is present and a
29776 DNS operation returns a temporary error, the verify condition succeeds.
29778 If this condition is used for a locally generated message (that is, when there
29779 is no client host involved), it always succeeds.
29781 .vitem &*verify&~=&~sender/*&<&'options'&>
29782 .cindex "&%verify%& ACL condition"
29783 .cindex "&ACL;" "verifying sender"
29784 .cindex "sender" "verifying"
29785 .cindex "verifying" "sender"
29786 This condition is relevant only after a MAIL or RCPT command, or after a
29787 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
29788 the message's sender is empty (that is, this is a bounce message), the
29789 condition is true. Otherwise, the sender address is verified.
29791 .vindex "&$address_data$&"
29792 .vindex "&$sender_address_data$&"
29793 If there is data in the &$address_data$& variable at the end of routing, its
29794 value is placed in &$sender_address_data$& at the end of verification. This
29795 value can be used in subsequent conditions and modifiers in the same ACL
29796 statement. It does not persist after the end of the current statement. If you
29797 want to preserve the value for longer, you can save it in an ACL variable.
29799 Details of verification are given later, starting at section
29800 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
29801 to avoid doing it more than once per message.
29803 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
29804 .cindex "&%verify%& ACL condition"
29805 This is a variation of the previous option, in which a modified address is
29806 verified as a sender.
29808 Note that '/' is legal in local-parts; if the address may have such
29809 (eg. is generated from the received message)
29810 they must be protected from the options parsing by doubling:
29812 verify = sender=${sg{${address:$h_sender:}}{/}{//}}
29818 .section "Using DNS lists" "SECTmorednslists"
29819 .cindex "DNS list" "in ACL"
29820 .cindex "black list (DNS)"
29821 .cindex "&ACL;" "testing a DNS list"
29822 In its simplest form, the &%dnslists%& condition tests whether the calling host
29823 is on at least one of a number of DNS lists by looking up the inverted IP
29824 address in one or more DNS domains. (Note that DNS list domains are not mail
29825 domains, so the &`+`& syntax for named lists doesn't work - it is used for
29826 special options instead.) For example, if the calling host's IP
29827 address is 192.168.62.43, and the ACL statement is
29829 deny dnslists = blackholes.mail-abuse.org : \
29830 dialups.mail-abuse.org
29832 the following records are looked up:
29834 43.62.168.192.blackholes.mail-abuse.org
29835 43.62.168.192.dialups.mail-abuse.org
29837 As soon as Exim finds an existing DNS record, processing of the list stops.
29838 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
29839 to test that a host is on more than one list (an &"and"& conjunction), you can
29840 use two separate conditions:
29842 deny dnslists = blackholes.mail-abuse.org
29843 dnslists = dialups.mail-abuse.org
29845 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
29846 behaves as if the host does not match the list item, that is, as if the DNS
29847 record does not exist. If there are further items in the DNS list, they are
29850 This is usually the required action when &%dnslists%& is used with &%deny%&
29851 (which is the most common usage), because it prevents a DNS failure from
29852 blocking mail. However, you can change this behaviour by putting one of the
29853 following special items in the list:
29855 &`+include_unknown `& behave as if the item is on the list
29856 &`+exclude_unknown `& behave as if the item is not on the list (default)
29857 &`+defer_unknown `& give a temporary error
29859 .cindex "&`+include_unknown`&"
29860 .cindex "&`+exclude_unknown`&"
29861 .cindex "&`+defer_unknown`&"
29862 Each of these applies to any subsequent items on the list. For example:
29864 deny dnslists = +defer_unknown : foo.bar.example
29866 Testing the list of domains stops as soon as a match is found. If you want to
29867 warn for one list and block for another, you can use two different statements:
29869 deny dnslists = blackholes.mail-abuse.org
29870 warn message = X-Warn: sending host is on dialups list
29871 dnslists = dialups.mail-abuse.org
29873 .cindex caching "of dns lookup"
29875 DNS list lookups are cached by Exim for the duration of the SMTP session
29876 (but limited by the DNS return TTL value),
29877 so a lookup based on the IP address is done at most once for any incoming
29878 connection (assuming long-enough TTL).
29879 Exim does not share information between multiple incoming
29880 connections (but your local name server cache should be active).
29884 .section "Specifying the IP address for a DNS list lookup" "SECID201"
29885 .cindex "DNS list" "keyed by explicit IP address"
29886 By default, the IP address that is used in a DNS list lookup is the IP address
29887 of the calling host. However, you can specify another IP address by listing it
29888 after the domain name, introduced by a slash. For example:
29890 deny dnslists = black.list.tld/192.168.1.2
29892 This feature is not very helpful with explicit IP addresses; it is intended for
29893 use with IP addresses that are looked up, for example, the IP addresses of the
29894 MX hosts or nameservers of an email sender address. For an example, see section
29895 &<<SECTmulkeyfor>>& below.
29900 .section "DNS lists keyed on domain names" "SECID202"
29901 .cindex "DNS list" "keyed by domain name"
29902 There are some lists that are keyed on domain names rather than inverted IP
29903 addresses (see for example the &'domain based zones'& link at
29904 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
29905 with these lists. You can change the name that is looked up in a DNS list by
29906 listing it after the domain name, introduced by a slash. For example,
29908 deny message = Sender's domain is listed at $dnslist_domain
29909 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
29911 This particular example is useful only in ACLs that are obeyed after the
29912 RCPT or DATA commands, when a sender address is available. If (for
29913 example) the message's sender is &'user@tld.example'& the name that is looked
29914 up by this example is
29916 tld.example.dsn.rfc-ignorant.org
29918 A single &%dnslists%& condition can contain entries for both names and IP
29919 addresses. For example:
29921 deny dnslists = sbl.spamhaus.org : \
29922 dsn.rfc-ignorant.org/$sender_address_domain
29924 The first item checks the sending host's IP address; the second checks a domain
29925 name. The whole condition is true if either of the DNS lookups succeeds.
29930 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
29931 .cindex "DNS list" "multiple keys for"
29932 The syntax described above for looking up explicitly-defined values (either
29933 names or IP addresses) in a DNS blacklist is a simplification. After the domain
29934 name for the DNS list, what follows the slash can in fact be a list of items.
29935 As with all lists in Exim, the default separator is a colon. However, because
29936 this is a sublist within the list of DNS blacklist domains, it is necessary
29937 either to double the separators like this:
29939 dnslists = black.list.tld/name.1::name.2
29941 or to change the separator character, like this:
29943 dnslists = black.list.tld/<;name.1;name.2
29945 If an item in the list is an IP address, it is inverted before the DNS
29946 blacklist domain is appended. If it is not an IP address, no inversion
29947 occurs. Consider this condition:
29949 dnslists = black.list.tld/<;192.168.1.2;a.domain
29951 The DNS lookups that occur are:
29953 2.1.168.192.black.list.tld
29954 a.domain.black.list.tld
29956 Once a DNS record has been found (that matches a specific IP return
29957 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
29958 are done. If there is a temporary DNS error, the rest of the sublist of domains
29959 or IP addresses is tried. A temporary error for the whole dnslists item occurs
29960 only if no other DNS lookup in this sublist succeeds. In other words, a
29961 successful lookup for any of the items in the sublist overrides a temporary
29962 error for a previous item.
29964 The ability to supply a list of items after the slash is in some sense just a
29965 syntactic convenience. These two examples have the same effect:
29967 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
29968 dnslists = black.list.tld/a.domain::b.domain
29970 However, when the data for the list is obtained from a lookup, the second form
29971 is usually much more convenient. Consider this example:
29973 deny message = The mail servers for the domain \
29974 $sender_address_domain \
29975 are listed at $dnslist_domain ($dnslist_value); \
29977 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
29978 ${lookup dnsdb {>|mxh=\
29979 $sender_address_domain} }} }
29981 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
29982 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
29983 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
29984 of expanding the condition might be something like this:
29986 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
29988 Thus, this example checks whether or not the IP addresses of the sender
29989 domain's mail servers are on the Spamhaus black list.
29991 The key that was used for a successful DNS list lookup is put into the variable
29992 &$dnslist_matched$& (see section &<<SECID204>>&).
29997 .section "Data returned by DNS lists" "SECID203"
29998 .cindex "DNS list" "data returned from"
29999 DNS lists are constructed using address records in the DNS. The original RBL
30000 just used the address 127.0.0.1 on the right hand side of each record, but the
30001 RBL+ list and some other lists use a number of values with different meanings.
30002 The values used on the RBL+ list are:
30006 127.1.0.3 DUL and RBL
30008 127.1.0.5 RSS and RBL
30009 127.1.0.6 RSS and DUL
30010 127.1.0.7 RSS and DUL and RBL
30012 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
30013 different values. Some DNS lists may return more than one address record;
30014 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
30017 .section "Variables set from DNS lists" "SECID204"
30018 .cindex "expansion" "variables, set from DNS list"
30019 .cindex "DNS list" "variables set from"
30020 .vindex "&$dnslist_domain$&"
30021 .vindex "&$dnslist_matched$&"
30022 .vindex "&$dnslist_text$&"
30023 .vindex "&$dnslist_value$&"
30024 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
30025 the name of the overall domain that matched (for example,
30026 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
30027 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
30028 the DNS record. When the key is an IP address, it is not reversed in
30029 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
30030 cases, for example:
30032 deny dnslists = spamhaus.example
30034 the key is also available in another variable (in this case,
30035 &$sender_host_address$&). In more complicated cases, however, this is not true.
30036 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
30037 might generate a dnslists lookup like this:
30039 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
30041 If this condition succeeds, the value in &$dnslist_matched$& might be
30042 &`192.168.6.7`& (for example).
30044 If more than one address record is returned by the DNS lookup, all the IP
30045 addresses are included in &$dnslist_value$&, separated by commas and spaces.
30046 The variable &$dnslist_text$& contains the contents of any associated TXT
30047 record. For lists such as RBL+ the TXT record for a merged entry is often not
30048 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
30051 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
30052 &-- although these appear before the condition in the ACL, they are not
30053 expanded until after it has failed. For example:
30055 deny hosts = !+local_networks
30056 message = $sender_host_address is listed \
30058 dnslists = rbl-plus.mail-abuse.example
30063 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
30064 .cindex "DNS list" "matching specific returned data"
30065 You can add an equals sign and an IP address after a &%dnslists%& domain name
30066 in order to restrict its action to DNS records with a matching right hand side.
30069 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
30071 rejects only those hosts that yield 127.0.0.2. Without this additional data,
30072 any address record is considered to be a match. For the moment, we assume
30073 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
30074 describes how multiple records are handled.
30076 More than one IP address may be given for checking, using a comma as a
30077 separator. These are alternatives &-- if any one of them matches, the
30078 &%dnslists%& condition is true. For example:
30080 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
30082 If you want to specify a constraining address list and also specify names or IP
30083 addresses to be looked up, the constraining address list must be specified
30084 first. For example:
30086 deny dnslists = dsn.rfc-ignorant.org\
30087 =127.0.0.2/$sender_address_domain
30090 If the character &`&&`& is used instead of &`=`&, the comparison for each
30091 listed IP address is done by a bitwise &"and"& instead of by an equality test.
30092 In other words, the listed addresses are used as bit masks. The comparison is
30093 true if all the bits in the mask are present in the address that is being
30094 tested. For example:
30096 dnslists = a.b.c&0.0.0.3
30098 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
30099 want to test whether one bit or another bit is present (as opposed to both
30100 being present), you must use multiple values. For example:
30102 dnslists = a.b.c&0.0.0.1,0.0.0.2
30104 matches if the final component of the address is an odd number or two times
30109 .section "Negated DNS matching conditions" "SECID205"
30110 You can supply a negative list of IP addresses as part of a &%dnslists%&
30113 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
30115 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
30116 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
30118 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
30120 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
30121 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
30122 words, the result of the test is inverted if an exclamation mark appears before
30123 the &`=`& (or the &`&&`&) sign.
30125 &*Note*&: This kind of negation is not the same as negation in a domain,
30126 host, or address list (which is why the syntax is different).
30128 If you are using just one list, the negation syntax does not gain you much. The
30129 previous example is precisely equivalent to
30131 deny dnslists = a.b.c
30132 !dnslists = a.b.c=127.0.0.2,127.0.0.3
30134 However, if you are using multiple lists, the negation syntax is clearer.
30135 Consider this example:
30137 deny dnslists = sbl.spamhaus.org : \
30139 dnsbl.njabl.org!=127.0.0.3 : \
30142 Using only positive lists, this would have to be:
30144 deny dnslists = sbl.spamhaus.org : \
30146 deny dnslists = dnsbl.njabl.org
30147 !dnslists = dnsbl.njabl.org=127.0.0.3
30148 deny dnslists = relays.ordb.org
30150 which is less clear, and harder to maintain.
30155 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
30156 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
30157 thereby providing more than one IP address. When an item in a &%dnslists%& list
30158 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
30159 the match to specific results from the DNS lookup, there are two ways in which
30160 the checking can be handled. For example, consider the condition:
30162 dnslists = a.b.c=127.0.0.1
30164 What happens if the DNS lookup for the incoming IP address yields both
30165 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
30166 condition true because at least one given value was found, or is it false
30167 because at least one of the found values was not listed? And how does this
30168 affect negated conditions? Both possibilities are provided for with the help of
30169 additional separators &`==`& and &`=&&`&.
30172 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
30173 IP addresses matches one of the listed addresses. For the example above, the
30174 condition is true because 127.0.0.1 matches.
30176 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
30177 looked up IP addresses matches one of the listed addresses. If the condition is
30180 dnslists = a.b.c==127.0.0.1
30182 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30183 false because 127.0.0.2 is not listed. You would need to have:
30185 dnslists = a.b.c==127.0.0.1,127.0.0.2
30187 for the condition to be true.
30190 When &`!`& is used to negate IP address matching, it inverts the result, giving
30191 the precise opposite of the behaviour above. Thus:
30193 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
30194 addresses matches one of the listed addresses. Consider:
30196 dnslists = a.b.c!&0.0.0.1
30198 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30199 false because 127.0.0.1 matches.
30201 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
30202 looked up IP address that does not match. Consider:
30204 dnslists = a.b.c!=&0.0.0.1
30206 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30207 true, because 127.0.0.2 does not match. You would need to have:
30209 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
30211 for the condition to be false.
30213 When the DNS lookup yields only a single IP address, there is no difference
30214 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
30219 .section "Detailed information from merged DNS lists" "SECTmordetinf"
30220 .cindex "DNS list" "information from merged"
30221 When the facility for restricting the matching IP values in a DNS list is used,
30222 the text from the TXT record that is set in &$dnslist_text$& may not reflect
30223 the true reason for rejection. This happens when lists are merged and the IP
30224 address in the A record is used to distinguish them; unfortunately there is
30225 only one TXT record. One way round this is not to use merged lists, but that
30226 can be inefficient because it requires multiple DNS lookups where one would do
30227 in the vast majority of cases when the host of interest is not on any of the
30230 A less inefficient way of solving this problem is available. If
30231 two domain names, comma-separated, are given, the second is used first to
30232 do an initial check, making use of any IP value restrictions that are set.
30233 If there is a match, the first domain is used, without any IP value
30234 restrictions, to get the TXT record. As a byproduct of this, there is also
30235 a check that the IP being tested is indeed on the first list. The first
30236 domain is the one that is put in &$dnslist_domain$&. For example:
30239 rejected because $sender_host_address is blacklisted \
30240 at $dnslist_domain\n$dnslist_text
30242 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
30243 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30245 For the first blacklist item, this starts by doing a lookup in
30246 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
30247 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
30248 value, and as long as something is found, it looks for the corresponding TXT
30249 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
30250 The second blacklist item is processed similarly.
30252 If you are interested in more than one merged list, the same list must be
30253 given several times, but because the results of the DNS lookups are cached,
30254 the DNS calls themselves are not repeated. For example:
30256 reject dnslists = \
30257 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
30258 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
30259 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
30260 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30262 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
30263 values matches (or if no record is found), this is the only lookup that is
30264 done. Only if there is a match is one of the more specific lists consulted.
30268 .section "DNS lists and IPv6" "SECTmorednslistslast"
30269 .cindex "IPv6" "DNS black lists"
30270 .cindex "DNS list" "IPv6 usage"
30271 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
30272 nibble by nibble. For example, if the calling host's IP address is
30273 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
30275 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
30276 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
30278 (split over two lines here to fit on the page). Unfortunately, some of the DNS
30279 lists contain wildcard records, intended for IPv4, that interact badly with
30280 IPv6. For example, the DNS entry
30282 *.3.some.list.example. A 127.0.0.1
30284 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
30285 Unfortunately, it also matches the entire 3::/4 IPv6 network.
30287 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
30288 &%condition%& condition, as in this example:
30290 deny condition = ${if isip4{$sender_host_address}}
30291 dnslists = some.list.example
30294 If an explicit key is being used for a DNS lookup and it may be an IPv6
30295 address you should specify alternate list separators for both the outer
30296 (DNS list name) list and inner (lookup keys) list:
30298 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
30301 .section "Rate limiting incoming messages" "SECTratelimiting"
30302 .cindex "rate limiting" "client sending"
30303 .cindex "limiting client sending rates"
30304 .oindex "&%smtp_ratelimit_*%&"
30305 The &%ratelimit%& ACL condition can be used to measure and control the rate at
30306 which clients can send email. This is more powerful than the
30307 &%smtp_ratelimit_*%& options, because those options control the rate of
30308 commands in a single SMTP session only, whereas the &%ratelimit%& condition
30309 works across all connections (concurrent and sequential) from the same client
30310 host. The syntax of the &%ratelimit%& condition is:
30312 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
30314 If the average client sending rate is less than &'m'& messages per time
30315 period &'p'& then the condition is false; otherwise it is true.
30317 As a side-effect, the &%ratelimit%& condition sets the expansion variable
30318 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
30319 configured value of &'m'&, and &$sender_rate_period$& to the configured value
30322 The parameter &'p'& is the smoothing time constant, in the form of an Exim
30323 time interval, for example, &`8h`& for eight hours. A larger time constant
30324 means that it takes Exim longer to forget a client's past behaviour. The
30325 parameter &'m'& is the maximum number of messages that a client is permitted to
30326 send in each time interval. It also specifies the number of messages permitted
30327 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
30328 constant, you can allow a client to send more messages in a burst without
30329 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
30330 both small, messages must be sent at an even rate.
30332 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
30333 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
30334 when deploying the &%ratelimit%& ACL condition. The script prints usage
30335 instructions when it is run with no arguments.
30337 The key is used to look up the data for calculating the client's average
30338 sending rate. This data is stored in Exim's spool directory, alongside the
30339 retry and other hints databases. The default key is &$sender_host_address$&,
30340 which means Exim computes the sending rate of each client host IP address.
30341 By changing the key you can change how Exim identifies clients for the purpose
30342 of ratelimiting. For example, to limit the sending rate of each authenticated
30343 user, independent of the computer they are sending from, set the key to
30344 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
30345 example, &$authenticated_id$& is only meaningful if the client has
30346 authenticated (which you can check with the &%authenticated%& ACL condition).
30348 The lookup key does not have to identify clients: If you want to limit the
30349 rate at which a recipient receives messages, you can use the key
30350 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
30353 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
30354 specifies what Exim measures the rate of, for example messages or recipients
30355 or bytes. You can adjust the measurement using the &%unique=%& and/or
30356 &%count=%& options. You can also control when Exim updates the recorded rate
30357 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
30358 separated by a slash, like the other parameters. They may appear in any order.
30360 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
30361 any options that alter the meaning of the stored data. The limit &'m'& is not
30362 stored, so you can alter the configured maximum rate and Exim will still
30363 remember clients' past behaviour. If you change the &%per_*%& mode or add or
30364 remove the &%unique=%& option, the lookup key changes so Exim will forget past
30365 behaviour. The lookup key is not affected by changes to the update mode and
30366 the &%count=%& option.
30369 .section "Ratelimit options for what is being measured" "ratoptmea"
30370 .cindex "rate limiting" "per_* options"
30371 The &%per_conn%& option limits the client's connection rate. It is not
30372 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
30373 &%acl_not_smtp_start%& ACLs.
30375 The &%per_mail%& option limits the client's rate of sending messages. This is
30376 the default if none of the &%per_*%& options is specified. It can be used in
30377 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
30378 &%acl_smtp_data%&, or &%acl_not_smtp%&.
30380 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
30381 the same ACLs as the &%per_mail%& option, though it is best to use this option
30382 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
30383 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
30384 in its MAIL command, which may be inaccurate or completely missing. You can
30385 follow the limit &'m'& in the configuration with K, M, or G to specify limits
30386 in kilobytes, megabytes, or gigabytes, respectively.
30388 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
30389 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
30390 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
30391 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
30392 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
30393 in either case the rate limiting engine will see a message with many
30394 recipients as a large high-speed burst.
30396 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
30397 number of different recipients that the client has sent messages to in the
30398 last time period. That is, if the client repeatedly sends messages to the same
30399 recipient, its measured rate is not increased. This option can only be used in
30402 The &%per_cmd%& option causes Exim to recompute the rate every time the
30403 condition is processed. This can be used to limit the rate of any SMTP
30404 command. If it is used in multiple ACLs it can limit the aggregate rate of
30405 multiple different commands.
30407 The &%count=%& option can be used to alter how much Exim adds to the client's
30408 measured rate. For example, the &%per_byte%& option is equivalent to
30409 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
30410 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
30411 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
30413 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
30416 .section "Ratelimit update modes" "ratoptupd"
30417 .cindex "rate limiting" "reading data without updating"
30418 You can specify one of three options with the &%ratelimit%& condition to
30419 control when its database is updated. This section describes the &%readonly%&
30420 mode, and the next section describes the &%strict%& and &%leaky%& modes.
30422 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
30423 previously-computed rate to check against the limit.
30425 For example, you can test the client's sending rate and deny it access (when
30426 it is too fast) in the connect ACL. If the client passes this check then it
30427 can go on to send a message, in which case its recorded rate will be updated
30428 in the MAIL ACL. Subsequent connections from the same client will check this
30432 deny ratelimit = 100 / 5m / readonly
30433 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
30434 (max $sender_rate_limit)
30437 warn ratelimit = 100 / 5m / strict
30438 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
30439 (max $sender_rate_limit)
30442 If Exim encounters multiple &%ratelimit%& conditions with the same key when
30443 processing a message then it may increase the client's measured rate more than
30444 it should. For example, this will happen if you check the &%per_rcpt%& option
30445 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
30446 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
30447 multiple update problems by using the &%readonly%& option on later ratelimit
30450 The &%per_*%& options described above do not make sense in some ACLs. If you
30451 use a &%per_*%& option in an ACL where it is not normally permitted then the
30452 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
30453 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
30454 next section) so you must specify the &%readonly%& option explicitly.
30457 .section "Ratelimit options for handling fast clients" "ratoptfast"
30458 .cindex "rate limiting" "strict and leaky modes"
30459 If a client's average rate is greater than the maximum, the rate limiting
30460 engine can react in two possible ways, depending on the presence of the
30461 &%strict%& or &%leaky%& update modes. This is independent of the other
30462 counter-measures (such as rejecting the message) that may be specified by the
30465 The &%leaky%& (default) option means that the client's recorded rate is not
30466 updated if it is above the limit. The effect of this is that Exim measures the
30467 client's average rate of successfully sent email, which cannot be greater than
30468 the maximum allowed. If the client is over the limit it may suffer some
30469 counter-measures (as specified in the ACL), but it will still be able to send
30470 email at the configured maximum rate, whatever the rate of its attempts. This
30471 is generally the better choice if you have clients that retry automatically.
30472 For example, it does not prevent a sender with an over-aggressive retry rate
30473 from getting any email through.
30475 The &%strict%& option means that the client's recorded rate is always
30476 updated. The effect of this is that Exim measures the client's average rate
30477 of attempts to send email, which can be much higher than the maximum it is
30478 actually allowed. If the client is over the limit it may be subjected to
30479 counter-measures by the ACL. It must slow down and allow sufficient time to
30480 pass that its computed rate falls below the maximum before it can send email
30481 again. The time (the number of smoothing periods) it must wait and not
30482 attempt to send mail can be calculated with this formula:
30484 ln(peakrate/maxrate)
30488 .section "Limiting the rate of different events" "ratoptuniq"
30489 .cindex "rate limiting" "counting unique events"
30490 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
30491 rate of different events. For example, the &%per_addr%& option uses this
30492 mechanism to count the number of different recipients that the client has
30493 sent messages to in the last time period; it is equivalent to
30494 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
30495 measure the rate that a client uses different sender addresses with the
30496 options &`per_mail/unique=$sender_address`&.
30498 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
30499 has seen for that key. The whole set is thrown away when it is older than the
30500 rate smoothing period &'p'&, so each different event is counted at most once
30501 per period. In the &%leaky%& update mode, an event that causes the client to
30502 go over the limit is not added to the set, in the same way that the client's
30503 recorded rate is not updated in the same situation.
30505 When you combine the &%unique=%& and &%readonly%& options, the specific
30506 &%unique=%& value is ignored, and Exim just retrieves the client's stored
30509 The &%unique=%& mechanism needs more space in the ratelimit database than the
30510 other &%ratelimit%& options in order to store the event set. The number of
30511 unique values is potentially as large as the rate limit, so the extra space
30512 required increases with larger limits.
30514 The uniqueification is not perfect: there is a small probability that Exim
30515 will think a new event has happened before. If the sender's rate is less than
30516 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
30517 the measured rate can go above the limit, in which case Exim may under-count
30518 events by a significant margin. Fortunately, if the rate is high enough (2.7
30519 times the limit) that the false positive rate goes above 9%, then Exim will
30520 throw away the over-full event set before the measured rate falls below the
30521 limit. Therefore the only harm should be that exceptionally high sending rates
30522 are logged incorrectly; any countermeasures you configure will be as effective
30526 .section "Using rate limiting" "useratlim"
30527 Exim's other ACL facilities are used to define what counter-measures are taken
30528 when the rate limit is exceeded. This might be anything from logging a warning
30529 (for example, while measuring existing sending rates in order to define
30530 policy), through time delays to slow down fast senders, up to rejecting the
30531 message. For example:
30533 # Log all senders' rates
30534 warn ratelimit = 0 / 1h / strict
30535 log_message = Sender rate $sender_rate / $sender_rate_period
30537 # Slow down fast senders; note the need to truncate $sender_rate
30538 # at the decimal point.
30539 warn ratelimit = 100 / 1h / per_rcpt / strict
30540 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
30541 $sender_rate_limit }s
30543 # Keep authenticated users under control
30544 deny authenticated = *
30545 ratelimit = 100 / 1d / strict / $authenticated_id
30547 # System-wide rate limit
30548 defer message = Sorry, too busy. Try again later.
30549 ratelimit = 10 / 1s / $primary_hostname
30551 # Restrict incoming rate from each host, with a default
30552 # set using a macro and special cases looked up in a table.
30553 defer message = Sender rate exceeds $sender_rate_limit \
30554 messages per $sender_rate_period
30555 ratelimit = ${lookup {$sender_host_address} \
30556 cdb {DB/ratelimits.cdb} \
30557 {$value} {RATELIMIT} }
30559 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
30560 especially with the &%per_rcpt%& option, you may suffer from a performance
30561 bottleneck caused by locking on the ratelimit hints database. Apart from
30562 making your ACLs less complicated, you can reduce the problem by using a
30563 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
30564 this means that Exim will lose its hints data after a reboot (including retry
30565 hints, the callout cache, and ratelimit data).
30569 .section "Address verification" "SECTaddressverification"
30570 .cindex "verifying address" "options for"
30571 .cindex "policy control" "address verification"
30572 Several of the &%verify%& conditions described in section
30573 &<<SECTaclconditions>>& cause addresses to be verified. Section
30574 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
30575 The verification conditions can be followed by options that modify the
30576 verification process. The options are separated from the keyword and from each
30577 other by slashes, and some of them contain parameters. For example:
30579 verify = sender/callout
30580 verify = recipient/defer_ok/callout=10s,defer_ok
30582 The first stage of address verification, which always happens, is to run the
30583 address through the routers, in &"verify mode"&. Routers can detect the
30584 difference between verification and routing for delivery, and their actions can
30585 be varied by a number of generic options such as &%verify%& and &%verify_only%&
30586 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
30587 The available options are as follows:
30590 If the &%callout%& option is specified, successful routing to one or more
30591 remote hosts is followed by a &"callout"& to those hosts as an additional
30592 check. Callouts and their sub-options are discussed in the next section.
30594 If there is a defer error while doing verification routing, the ACL
30595 normally returns &"defer"&. However, if you include &%defer_ok%& in the
30596 options, the condition is forced to be true instead. Note that this is a main
30597 verification option as well as a suboption for callouts.
30599 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
30600 discusses the reporting of sender address verification failures.
30602 The &%success_on_redirect%& option causes verification always to succeed
30603 immediately after a successful redirection. By default, if a redirection
30604 generates just one address, that address is also verified. See further
30605 discussion in section &<<SECTredirwhilveri>>&.
30608 .cindex "verifying address" "differentiating failures"
30609 .vindex "&$recipient_verify_failure$&"
30610 .vindex "&$sender_verify_failure$&"
30611 .vindex "&$acl_verify_message$&"
30612 After an address verification failure, &$acl_verify_message$& contains the
30613 error message that is associated with the failure. It can be preserved by
30616 warn !verify = sender
30617 set acl_m0 = $acl_verify_message
30619 If you are writing your own custom rejection message or log message when
30620 denying access, you can use this variable to include information about the
30621 verification failure.
30623 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
30624 appropriate) contains one of the following words:
30627 &%qualify%&: The address was unqualified (no domain), and the message
30628 was neither local nor came from an exempted host.
30630 &%route%&: Routing failed.
30632 &%mail%&: Routing succeeded, and a callout was attempted; rejection
30633 occurred at or before the MAIL command (that is, on initial
30634 connection, HELO, or MAIL).
30636 &%recipient%&: The RCPT command in a callout was rejected.
30638 &%postmaster%&: The postmaster check in a callout was rejected.
30641 The main use of these variables is expected to be to distinguish between
30642 rejections of MAIL and rejections of RCPT in callouts.
30647 .section "Callout verification" "SECTcallver"
30648 .cindex "verifying address" "by callout"
30649 .cindex "callout" "verification"
30650 .cindex "SMTP" "callout verification"
30651 For non-local addresses, routing verifies the domain, but is unable to do any
30652 checking of the local part. There are situations where some means of verifying
30653 the local part is desirable. One way this can be done is to make an SMTP
30654 &'callback'& to a delivery host for the sender address or a &'callforward'& to
30655 a subsequent host for a recipient address, to see if the host accepts the
30656 address. We use the term &'callout'& to cover both cases. Note that for a
30657 sender address, the callback is not to the client host that is trying to
30658 deliver the message, but to one of the hosts that accepts incoming mail for the
30661 Exim does not do callouts by default. If you want them to happen, you must
30662 request them by setting appropriate options on the &%verify%& condition, as
30663 described below. This facility should be used with care, because it can add a
30664 lot of resource usage to the cost of verifying an address. However, Exim does
30665 cache the results of callouts, which helps to reduce the cost. Details of
30666 caching are in section &<<SECTcallvercache>>&.
30668 Recipient callouts are usually used only between hosts that are controlled by
30669 the same administration. For example, a corporate gateway host could use
30670 callouts to check for valid recipients on an internal mailserver. A successful
30671 callout does not guarantee that a real delivery to the address would succeed;
30672 on the other hand, a failing callout does guarantee that a delivery would fail.
30674 If the &%callout%& option is present on a condition that verifies an address, a
30675 second stage of verification occurs if the address is successfully routed to
30676 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
30677 &(manualroute)& router, where the router specifies the hosts. However, if a
30678 router that does not set up hosts routes to an &(smtp)& transport with a
30679 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
30680 &%hosts_override%& set, its hosts are always used, whether or not the router
30681 supplies a host list.
30682 Callouts are only supported on &(smtp)& transports.
30684 The port that is used is taken from the transport, if it is specified and is a
30685 remote transport. (For routers that do verification only, no transport need be
30686 specified.) Otherwise, the default SMTP port is used. If a remote transport
30687 specifies an outgoing interface, this is used; otherwise the interface is not
30688 specified. Likewise, the text that is used for the HELO command is taken from
30689 the transport's &%helo_data%& option; if there is no transport, the value of
30690 &$smtp_active_hostname$& is used.
30692 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
30693 test whether a bounce message could be delivered to the sender address. The
30694 following SMTP commands are sent:
30696 &`HELO `&<&'local host name'&>
30698 &`RCPT TO:`&<&'the address to be tested'&>
30701 LHLO is used instead of HELO if the transport's &%protocol%& option is
30704 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
30707 A recipient callout check is similar. By default, it also uses an empty address
30708 for the sender. This default is chosen because most hosts do not make use of
30709 the sender address when verifying a recipient. Using the same address means
30710 that a single cache entry can be used for each recipient. Some sites, however,
30711 do make use of the sender address when verifying. These are catered for by the
30712 &%use_sender%& and &%use_postmaster%& options, described in the next section.
30714 If the response to the RCPT command is a 2&'xx'& code, the verification
30715 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
30716 Exim tries the next host, if any. If there is a problem with all the remote
30717 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
30718 &%callout%& option is given, in which case the condition is forced to succeed.
30720 .cindex "SMTP" "output flushing, disabling for callout"
30721 A callout may take a little time. For this reason, Exim normally flushes SMTP
30722 output before performing a callout in an ACL, to avoid unexpected timeouts in
30723 clients when the SMTP PIPELINING extension is in use. The flushing can be
30724 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
30729 .section "Additional parameters for callouts" "CALLaddparcall"
30730 .cindex "callout" "additional parameters for"
30731 The &%callout%& option can be followed by an equals sign and a number of
30732 optional parameters, separated by commas. For example:
30734 verify = recipient/callout=10s,defer_ok
30736 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
30737 separate verify options, is retained for backwards compatibility, but is now
30738 deprecated. The additional parameters for &%callout%& are as follows:
30742 .vitem <&'a&~time&~interval'&>
30743 .cindex "callout" "timeout, specifying"
30744 This specifies the timeout that applies for the callout attempt to each host.
30747 verify = sender/callout=5s
30749 The default is 30 seconds. The timeout is used for each response from the
30750 remote host. It is also used for the initial connection, unless overridden by
30751 the &%connect%& parameter.
30754 .vitem &*connect&~=&~*&<&'time&~interval'&>
30755 .cindex "callout" "connection timeout, specifying"
30756 This parameter makes it possible to set a different (usually smaller) timeout
30757 for making the SMTP connection. For example:
30759 verify = sender/callout=5s,connect=1s
30761 If not specified, this timeout defaults to the general timeout value.
30763 .vitem &*defer_ok*&
30764 .cindex "callout" "defer, action on"
30765 When this parameter is present, failure to contact any host, or any other kind
30766 of temporary error, is treated as success by the ACL. However, the cache is not
30767 updated in this circumstance.
30769 .vitem &*fullpostmaster*&
30770 .cindex "callout" "full postmaster check"
30771 This operates like the &%postmaster%& option (see below), but if the check for
30772 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
30773 accordance with the specification in RFC 2821. The RFC states that the
30774 unqualified address &'postmaster'& should be accepted.
30777 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
30778 .cindex "callout" "sender when verifying header"
30779 When verifying addresses in header lines using the &%header_sender%&
30780 verification option, Exim behaves by default as if the addresses are envelope
30781 sender addresses from a message. Callout verification therefore tests to see
30782 whether a bounce message could be delivered, by using an empty address in the
30783 MAIL command. However, it is arguable that these addresses might never be used
30784 as envelope senders, and could therefore justifiably reject bounce messages
30785 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
30786 address to use in the MAIL command. For example:
30788 require verify = header_sender/callout=mailfrom=abcd@x.y.z
30790 This parameter is available only for the &%header_sender%& verification option.
30793 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
30794 .cindex "callout" "overall timeout, specifying"
30795 This parameter sets an overall timeout for performing a callout verification.
30798 verify = sender/callout=5s,maxwait=30s
30800 This timeout defaults to four times the callout timeout for individual SMTP
30801 commands. The overall timeout applies when there is more than one host that can
30802 be tried. The timeout is checked before trying the next host. This prevents
30803 very long delays if there are a large number of hosts and all are timing out
30804 (for example, when network connections are timing out).
30807 .vitem &*no_cache*&
30808 .cindex "callout" "cache, suppressing"
30809 .cindex "caching callout, suppressing"
30810 When this parameter is given, the callout cache is neither read nor updated.
30812 .vitem &*postmaster*&
30813 .cindex "callout" "postmaster; checking"
30814 When this parameter is set, a successful callout check is followed by a similar
30815 check for the local part &'postmaster'& at the same domain. If this address is
30816 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
30817 the postmaster check is recorded in a cache record; if it is a failure, this is
30818 used to fail subsequent callouts for the domain without a connection being
30819 made, until the cache record expires.
30821 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
30822 The postmaster check uses an empty sender in the MAIL command by default.
30823 You can use this parameter to do a postmaster check using a different address.
30826 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
30828 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
30829 one overrides. The &%postmaster%& parameter is equivalent to this example:
30831 require verify = sender/callout=postmaster_mailfrom=
30833 &*Warning*&: The caching arrangements for postmaster checking do not take
30834 account of the sender address. It is assumed that either the empty address or
30835 a fixed non-empty address will be used. All that Exim remembers is that the
30836 postmaster check for the domain succeeded or failed.
30840 .cindex "callout" "&""random""& check"
30841 When this parameter is set, before doing the normal callout check, Exim does a
30842 check for a &"random"& local part at the same domain. The local part is not
30843 really random &-- it is defined by the expansion of the option
30844 &%callout_random_local_part%&, which defaults to
30846 $primary_hostname-$tod_epoch-testing
30848 The idea here is to try to determine whether the remote host accepts all local
30849 parts without checking. If it does, there is no point in doing callouts for
30850 specific local parts. If the &"random"& check succeeds, the result is saved in
30851 a cache record, and used to force the current and subsequent callout checks to
30852 succeed without a connection being made, until the cache record expires.
30854 .vitem &*use_postmaster*&
30855 .cindex "callout" "sender for recipient check"
30856 This parameter applies to recipient callouts only. For example:
30858 deny !verify = recipient/callout=use_postmaster
30860 .vindex "&$qualify_domain$&"
30861 It causes a non-empty postmaster address to be used in the MAIL command when
30862 performing the callout for the recipient, and also for a &"random"& check if
30863 that is configured. The local part of the address is &`postmaster`& and the
30864 domain is the contents of &$qualify_domain$&.
30866 .vitem &*use_sender*&
30867 This option applies to recipient callouts only. For example:
30869 require verify = recipient/callout=use_sender
30871 It causes the message's actual sender address to be used in the MAIL
30872 command when performing the callout, instead of an empty address. There is no
30873 need to use this option unless you know that the called hosts make use of the
30874 sender when checking recipients. If used indiscriminately, it reduces the
30875 usefulness of callout caching.
30878 If you use any of the parameters that set a non-empty sender for the MAIL
30879 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
30880 &%use_sender%&), you should think about possible loops. Recipient checking is
30881 usually done between two hosts that are under the same management, and the host
30882 that receives the callouts is not normally configured to do callouts itself.
30883 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
30884 these circumstances.
30886 However, if you use a non-empty sender address for a callout to an arbitrary
30887 host, there is the likelihood that the remote host will itself initiate a
30888 callout check back to your host. As it is checking what appears to be a message
30889 sender, it is likely to use an empty address in MAIL, thus avoiding a
30890 callout loop. However, to be on the safe side it would be best to set up your
30891 own ACLs so that they do not do sender verification checks when the recipient
30892 is the address you use for header sender or postmaster callout checking.
30894 Another issue to think about when using non-empty senders for callouts is
30895 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
30896 by the sender/recipient combination; thus, for any given recipient, many more
30897 actual callouts are performed than when an empty sender or postmaster is used.
30902 .section "Callout caching" "SECTcallvercache"
30903 .cindex "hints database" "callout cache"
30904 .cindex "callout" "cache, description of"
30905 .cindex "caching" "callout"
30906 Exim caches the results of callouts in order to reduce the amount of resources
30907 used, unless you specify the &%no_cache%& parameter with the &%callout%&
30908 option. A hints database called &"callout"& is used for the cache. Two
30909 different record types are used: one records the result of a callout check for
30910 a specific address, and the other records information that applies to the
30911 entire domain (for example, that it accepts the local part &'postmaster'&).
30913 When an original callout fails, a detailed SMTP error message is given about
30914 the failure. However, for subsequent failures use the cache data, this message
30917 The expiry times for negative and positive address cache records are
30918 independent, and can be set by the global options &%callout_negative_expire%&
30919 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
30921 If a host gives a negative response to an SMTP connection, or rejects any
30922 commands up to and including
30926 (but not including the MAIL command with a non-empty address),
30927 any callout attempt is bound to fail. Exim remembers such failures in a
30928 domain cache record, which it uses to fail callouts for the domain without
30929 making new connections, until the domain record times out. There are two
30930 separate expiry times for domain cache records:
30931 &%callout_domain_negative_expire%& (default 3h) and
30932 &%callout_domain_positive_expire%& (default 7d).
30934 Domain records expire when the negative expiry time is reached if callouts
30935 cannot be made for the domain, or if the postmaster check failed.
30936 Otherwise, they expire when the positive expiry time is reached. This
30937 ensures that, for example, a host that stops accepting &"random"& local parts
30938 will eventually be noticed.
30940 The callout caching mechanism is based on the domain of the address that is
30941 being tested. If the domain routes to several hosts, it is assumed that their
30942 behaviour will be the same.
30946 .section "Sender address verification reporting" "SECTsenaddver"
30947 .cindex "verifying" "suppressing error details"
30948 See section &<<SECTaddressverification>>& for a general discussion of
30949 verification. When sender verification fails in an ACL, the details of the
30950 failure are given as additional output lines before the 550 response to the
30951 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
30954 MAIL FROM:<xyz@abc.example>
30956 RCPT TO:<pqr@def.example>
30957 550-Verification failed for <xyz@abc.example>
30958 550-Called: 192.168.34.43
30959 550-Sent: RCPT TO:<xyz@abc.example>
30960 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
30961 550 Sender verification failed
30963 If more than one RCPT command fails in the same way, the details are given
30964 only for the first of them. However, some administrators do not want to send
30965 out this much information. You can suppress the details by adding
30966 &`/no_details`& to the ACL statement that requests sender verification. For
30969 verify = sender/no_details
30972 .section "Redirection while verifying" "SECTredirwhilveri"
30973 .cindex "verifying" "redirection while"
30974 .cindex "address redirection" "while verifying"
30975 A dilemma arises when a local address is redirected by aliasing or forwarding
30976 during verification: should the generated addresses themselves be verified,
30977 or should the successful expansion of the original address be enough to verify
30978 it? By default, Exim takes the following pragmatic approach:
30981 When an incoming address is redirected to just one child address, verification
30982 continues with the child address, and if that fails to verify, the original
30983 verification also fails.
30985 When an incoming address is redirected to more than one child address,
30986 verification does not continue. A success result is returned.
30989 This seems the most reasonable behaviour for the common use of aliasing as a
30990 way of redirecting different local parts to the same mailbox. It means, for
30991 example, that a pair of alias entries of the form
30994 aw123: :fail: Gone away, no forwarding address
30996 work as expected, with both local parts causing verification failure. When a
30997 redirection generates more than one address, the behaviour is more like a
30998 mailing list, where the existence of the alias itself is sufficient for
30999 verification to succeed.
31001 It is possible, however, to change the default behaviour so that all successful
31002 redirections count as successful verifications, however many new addresses are
31003 generated. This is specified by the &%success_on_redirect%& verification
31004 option. For example:
31006 require verify = recipient/success_on_redirect/callout=10s
31008 In this example, verification succeeds if a router generates a new address, and
31009 the callout does not occur, because no address was routed to a remote host.
31011 When verification is being tested via the &%-bv%& option, the treatment of
31012 redirections is as just described, unless the &%-v%& or any debugging option is
31013 also specified. In that case, full verification is done for every generated
31014 address and a report is output for each of them.
31018 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
31019 .cindex "CSA" "verifying"
31020 Client SMTP Authorization is a system that allows a site to advertise
31021 which machines are and are not permitted to send email. This is done by placing
31022 special SRV records in the DNS; these are looked up using the client's HELO
31023 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
31024 Authorization checks in Exim are performed by the ACL condition:
31028 This fails if the client is not authorized. If there is a DNS problem, or if no
31029 valid CSA SRV record is found, or if the client is authorized, the condition
31030 succeeds. These three cases can be distinguished using the expansion variable
31031 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
31032 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
31033 be likely to cause problems for legitimate email.
31035 The error messages produced by the CSA code include slightly more
31036 detail. If &$csa_status$& is &"defer"&, this may be because of problems
31037 looking up the CSA SRV record, or problems looking up the CSA target
31038 address record. There are four reasons for &$csa_status$& being &"fail"&:
31041 The client's host name is explicitly not authorized.
31043 The client's IP address does not match any of the CSA target IP addresses.
31045 The client's host name is authorized but it has no valid target IP addresses
31046 (for example, the target's addresses are IPv6 and the client is using IPv4).
31048 The client's host name has no CSA SRV record but a parent domain has asserted
31049 that all subdomains must be explicitly authorized.
31052 The &%csa%& verification condition can take an argument which is the domain to
31053 use for the DNS query. The default is:
31055 verify = csa/$sender_helo_name
31057 This implementation includes an extension to CSA. If the query domain
31058 is an address literal such as [192.0.2.95], or if it is a bare IP
31059 address, Exim searches for CSA SRV records in the reverse DNS as if
31060 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
31063 verify = csa/$sender_host_address
31065 In fact, this is the check that Exim performs if the client does not say HELO.
31066 This extension can be turned off by setting the main configuration option
31067 &%dns_csa_use_reverse%& to be false.
31069 If a CSA SRV record is not found for the domain itself, a search
31070 is performed through its parent domains for a record which might be
31071 making assertions about subdomains. The maximum depth of this search is limited
31072 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
31073 default. Exim does not look for CSA SRV records in a top level domain, so the
31074 default settings handle HELO domains as long as seven
31075 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
31076 of legitimate HELO domains.
31078 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
31079 direct SRV lookups, this is not sufficient because of the extra parent domain
31080 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
31081 addresses into lookups in the reverse DNS space. The result of a successful
31084 ${lookup dnsdb {csa=$sender_helo_name}}
31086 has two space-separated fields: an authorization code and a target host name.
31087 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
31088 authorization required but absent, or &"?"& for unknown.
31093 .section "Bounce address tag validation" "SECTverifyPRVS"
31094 .cindex "BATV, verifying"
31095 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
31096 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
31097 Genuine incoming bounce messages should therefore always be addressed to
31098 recipients that have a valid tag. This scheme is a way of detecting unwanted
31099 bounce messages caused by sender address forgeries (often called &"collateral
31100 spam"&), because the recipients of such messages do not include valid tags.
31102 There are two expansion items to help with the implementation of the BATV
31103 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
31104 the original envelope sender address by using a simple key to add a hash of the
31105 address and some time-based randomizing information. The &%prvs%& expansion
31106 item creates a signed address, and the &%prvscheck%& expansion item checks one.
31107 The syntax of these expansion items is described in section
31108 &<<SECTexpansionitems>>&.
31110 As an example, suppose the secret per-address keys are stored in an MySQL
31111 database. A query to look up the key for an address could be defined as a macro
31114 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
31115 WHERE sender='${quote_mysql:$prvscheck_address}'\
31118 Suppose also that the senders who make use of BATV are defined by an address
31119 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
31122 # Bounces: drop unsigned addresses for BATV senders
31123 deny message = This address does not send an unsigned reverse path
31125 recipients = +batv_senders
31127 # Bounces: In case of prvs-signed address, check signature.
31128 deny message = Invalid reverse path signature.
31130 condition = ${prvscheck {$local_part@$domain}\
31131 {PRVSCHECK_SQL}{1}}
31132 !condition = $prvscheck_result
31134 The first statement rejects recipients for bounce messages that are addressed
31135 to plain BATV sender addresses, because it is known that BATV senders do not
31136 send out messages with plain sender addresses. The second statement rejects
31137 recipients that are prvs-signed, but with invalid signatures (either because
31138 the key is wrong, or the signature has timed out).
31140 A non-prvs-signed address is not rejected by the second statement, because the
31141 &%prvscheck%& expansion yields an empty string if its first argument is not a
31142 prvs-signed address, thus causing the &%condition%& condition to be false. If
31143 the first argument is a syntactically valid prvs-signed address, the yield is
31144 the third string (in this case &"1"&), whether or not the cryptographic and
31145 timeout checks succeed. The &$prvscheck_result$& variable contains the result
31146 of the checks (empty for failure, &"1"& for success).
31148 There is one more issue you must consider when implementing prvs-signing:
31149 you have to ensure that the routers accept prvs-signed addresses and
31150 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
31151 router to remove the signature with a configuration along these lines:
31155 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
31157 This works because, if the third argument of &%prvscheck%& is empty, the result
31158 of the expansion of a prvs-signed address is the decoded value of the original
31159 address. This router should probably be the first of your routers that handles
31162 To create BATV-signed addresses in the first place, a transport of this form
31165 external_smtp_batv:
31167 return_path = ${prvs {$return_path} \
31168 {${lookup mysql{SELECT \
31169 secret FROM batv_prvs WHERE \
31170 sender='${quote_mysql:$sender_address}'} \
31173 If no key can be found for the existing return path, no signing takes place.
31177 .section "Using an ACL to control relaying" "SECTrelaycontrol"
31178 .cindex "&ACL;" "relay control"
31179 .cindex "relaying" "control by ACL"
31180 .cindex "policy control" "relay control"
31181 An MTA is said to &'relay'& a message if it receives it from some host and
31182 delivers it directly to another host as a result of a remote address contained
31183 within it. Redirecting a local address via an alias or forward file and then
31184 passing the message on to another host is not relaying,
31185 .cindex "&""percent hack""&"
31186 but a redirection as a result of the &"percent hack"& is.
31188 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
31189 A host which is acting as a gateway or an MX backup is concerned with incoming
31190 relaying from arbitrary hosts to a specific set of domains. On the other hand,
31191 a host which is acting as a smart host for a number of clients is concerned
31192 with outgoing relaying from those clients to the Internet at large. Often the
31193 same host is fulfilling both functions,
31195 . as illustrated in the diagram below,
31197 but in principle these two kinds of relaying are entirely independent. What is
31198 not wanted is the transmission of mail from arbitrary remote hosts through your
31199 system to arbitrary domains.
31202 You can implement relay control by means of suitable statements in the ACL that
31203 runs for each RCPT command. For convenience, it is often easiest to use
31204 Exim's named list facility to define the domains and hosts involved. For
31205 example, suppose you want to do the following:
31208 Deliver a number of domains to mailboxes on the local host (or process them
31209 locally in some other way). Let's say these are &'my.dom1.example'& and
31210 &'my.dom2.example'&.
31212 Relay mail for a number of other domains for which you are the secondary MX.
31213 These might be &'friend1.example'& and &'friend2.example'&.
31215 Relay mail from the hosts on your local LAN, to whatever domains are involved.
31216 Suppose your LAN is 192.168.45.0/24.
31220 In the main part of the configuration, you put the following definitions:
31222 domainlist local_domains = my.dom1.example : my.dom2.example
31223 domainlist relay_to_domains = friend1.example : friend2.example
31224 hostlist relay_from_hosts = 192.168.45.0/24
31226 Now you can use these definitions in the ACL that is run for every RCPT
31230 accept domains = +local_domains : +relay_to_domains
31231 accept hosts = +relay_from_hosts
31233 The first statement accepts any RCPT command that contains an address in
31234 the local or relay domains. For any other domain, control passes to the second
31235 statement, which accepts the command only if it comes from one of the relay
31236 hosts. In practice, you will probably want to make your ACL more sophisticated
31237 than this, for example, by including sender and recipient verification. The
31238 default configuration includes a more comprehensive example, which is described
31239 in chapter &<<CHAPdefconfil>>&.
31243 .section "Checking a relay configuration" "SECTcheralcon"
31244 .cindex "relaying" "checking control of"
31245 You can check the relay characteristics of your configuration in the same way
31246 that you can test any ACL behaviour for an incoming SMTP connection, by using
31247 the &%-bh%& option to run a fake SMTP session with which you interact.
31252 . ////////////////////////////////////////////////////////////////////////////
31253 . ////////////////////////////////////////////////////////////////////////////
31255 .chapter "Content scanning at ACL time" "CHAPexiscan"
31256 .scindex IIDcosca "content scanning" "at ACL time"
31257 The extension of Exim to include content scanning at ACL time, formerly known
31258 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
31259 was integrated into the main source for Exim release 4.50, and Tom continues to
31260 maintain it. Most of the wording of this chapter is taken from Tom's
31263 It is also possible to scan the content of messages at other times. The
31264 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
31265 scanning after all the ACLs have run. A transport filter can be used to scan
31266 messages at delivery time (see the &%transport_filter%& option, described in
31267 chapter &<<CHAPtransportgeneric>>&).
31269 If you want to include the ACL-time content-scanning features when you compile
31270 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
31271 &_Local/Makefile_&. When you do that, the Exim binary is built with:
31274 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
31275 for all MIME parts for SMTP and non-SMTP messages, respectively.
31277 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
31278 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
31279 run at the end of message reception (the &%acl_smtp_data%& ACL).
31281 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
31282 of messages, or parts of messages, for debugging purposes.
31284 Additional expansion variables that are set in the new ACL and by the new
31287 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
31290 Content-scanning is continually evolving, and new features are still being
31291 added. While such features are still unstable and liable to incompatible
31292 changes, they are made available in Exim by setting options whose names begin
31293 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
31294 this manual. You can find out about them by reading the file called
31295 &_doc/experimental.txt_&.
31297 All the content-scanning facilities work on a MBOX copy of the message that is
31298 temporarily created in a file called:
31300 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
31302 The &_.eml_& extension is a friendly hint to virus scanners that they can
31303 expect an MBOX-like structure inside that file. The file is created when the
31304 first content scanning facility is called. Subsequent calls to content
31305 scanning conditions open the same file again. The directory is recursively
31306 removed when the &%acl_smtp_data%& ACL has finished running, unless
31308 control = no_mbox_unspool
31310 has been encountered. When the MIME ACL decodes files, they are put into the
31311 same directory by default.
31315 .section "Scanning for viruses" "SECTscanvirus"
31316 .cindex "virus scanning"
31317 .cindex "content scanning" "for viruses"
31318 .cindex "content scanning" "the &%malware%& condition"
31319 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
31320 It supports a &"generic"& interface to scanners called via the shell, and
31321 specialized interfaces for &"daemon"& type virus scanners, which are resident
31322 in memory and thus are much faster.
31324 A timeout of 2 minutes is applied to a scanner call (by default);
31325 if it expires then a defer action is taken.
31327 .oindex "&%av_scanner%&"
31328 You can set the &%av_scanner%& option in the main part of the configuration
31329 to specify which scanner to use, together with any additional options that
31330 are needed. The basic syntax is as follows:
31332 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
31334 If you do not set &%av_scanner%&, it defaults to
31336 av_scanner = sophie:/var/run/sophie
31338 If the value of &%av_scanner%& starts with a dollar character, it is expanded
31340 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
31341 The following scanner types are supported in this release:
31345 .cindex "virus scanners" "avast"
31346 This is the scanner daemon of Avast. It has been tested with Avast Core
31347 Security (currently at version 1.1.7).
31348 You can get a trial version at &url(http://www.avast.com) or for Linux
31349 at &url(http://www.avast.com/linux-server-antivirus).
31350 This scanner type takes one option,
31351 which can be either a full path to a UNIX socket,
31352 or host and port specifiers separated by white space.
31353 The host may be a name or an IP address; the port is either a
31354 single number or a pair of numbers with a dash between.
31355 Any further options are given, on separate lines,
31356 to the daemon as options before the main scan command.
31359 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
31360 av_scanner = avast:192.168.2.22 5036
31362 If you omit the argument, the default path
31363 &_/var/run/avast/scan.sock_&
31365 If you use a remote host,
31366 you need to make Exim's spool directory available to it,
31367 as the scanner is passed a file path, not file contents.
31368 For information about available commands and their options you may use
31370 $ socat UNIX:/var/run/avast/scan.sock STDIO:
31377 .vitem &%aveserver%&
31378 .cindex "virus scanners" "Kaspersky"
31379 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
31380 at &url(http://www.kaspersky.com). This scanner type takes one option,
31381 which is the path to the daemon's UNIX socket. The default is shown in this
31384 av_scanner = aveserver:/var/run/aveserver
31389 .cindex "virus scanners" "clamd"
31390 This daemon-type scanner is GPL and free. You can get it at
31391 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
31392 unpack MIME containers, so it used to be recommended to unpack MIME attachments
31393 in the MIME ACL. This is no longer believed to be necessary.
31395 The options are a list of server specifiers, which may be
31396 a UNIX socket specification,
31397 a TCP socket specification,
31398 or a (global) option.
31400 A socket specification consists of a space-separated list.
31401 For a Unix socket the first element is a full path for the socket,
31402 for a TCP socket the first element is the IP address
31403 and the second a port number,
31404 Any further elements are per-server (non-global) options.
31405 These per-server options are supported:
31407 retry=<timespec> Retry on connect fail
31410 The &`retry`& option specifies a time after which a single retry for
31411 a failed connect is made. The default is to not retry.
31413 If a Unix socket file is specified, only one server is supported.
31417 av_scanner = clamd:/opt/clamd/socket
31418 av_scanner = clamd:192.0.2.3 1234
31419 av_scanner = clamd:192.0.2.3 1234:local
31420 av_scanner = clamd:192.0.2.3 1234 retry=10s
31421 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
31423 If the value of av_scanner points to a UNIX socket file or contains the
31425 option, then the ClamAV interface will pass a filename containing the data
31426 to be scanned, which will should normally result in less I/O happening and be
31427 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
31428 Exim does not assume that there is a common filesystem with the remote host.
31429 There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should
31430 you be running a version of ClamAV prior to 0.95.
31432 The final example shows that multiple TCP targets can be specified. Exim will
31433 randomly use one for each incoming email (i.e. it load balances them). Note
31434 that only TCP targets may be used if specifying a list of scanners; a UNIX
31435 socket cannot be mixed in with TCP targets. If one of the servers becomes
31436 unavailable, Exim will try the remaining one(s) until it finds one that works.
31437 When a clamd server becomes unreachable, Exim will log a message. Exim does
31438 not keep track of scanner state between multiple messages, and the scanner
31439 selection is random, so the message will get logged in the mainlog for each
31440 email that the down scanner gets chosen first (message wrapped to be readable):
31442 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
31443 clamd: connection to localhost, port 3310 failed
31444 (Connection refused)
31447 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
31448 contributing the code for this scanner.
31451 .cindex "virus scanners" "command line interface"
31452 This is the keyword for the generic command line scanner interface. It can be
31453 used to attach virus scanners that are invoked from the shell. This scanner
31454 type takes 3 mandatory options:
31457 The full path and name of the scanner binary, with all command line options,
31458 and a placeholder (&`%s`&) for the directory to scan.
31461 A regular expression to match against the STDOUT and STDERR output of the
31462 virus scanner. If the expression matches, a virus was found. You must make
31463 absolutely sure that this expression matches on &"virus found"&. This is called
31464 the &"trigger"& expression.
31467 Another regular expression, containing exactly one pair of parentheses, to
31468 match the name of the virus found in the scanners output. This is called the
31469 &"name"& expression.
31472 For example, Sophos Sweep reports a virus on a line like this:
31474 Virus 'W32/Magistr-B' found in file ./those.bat
31476 For the trigger expression, we can match the phrase &"found in file"&. For the
31477 name expression, we want to extract the W32/Magistr-B string, so we can match
31478 for the single quotes left and right of it. Altogether, this makes the
31479 configuration setting:
31481 av_scanner = cmdline:\
31482 /path/to/sweep -ss -all -rec -archive %s:\
31483 found in file:'(.+)'
31486 .cindex "virus scanners" "DrWeb"
31487 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
31489 either a full path to a UNIX socket,
31490 or host and port specifiers separated by white space.
31491 The host may be a name or an IP address; the port is either a
31492 single number or a pair of numbers with a dash between.
31495 av_scanner = drweb:/var/run/drwebd.sock
31496 av_scanner = drweb:192.168.2.20 31337
31498 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
31499 is used. Thanks to Alex Miller for contributing the code for this scanner.
31502 .cindex "virus scanners" "f-protd"
31503 The f-protd scanner is accessed via HTTP over TCP.
31504 One argument is taken, being a space-separated hostname and port number
31508 av_scanner = f-protd:localhost 10200-10204
31510 If you omit the argument, the default values show above are used.
31513 .cindex "virus scanners" "F-Secure"
31514 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
31515 argument which is the path to a UNIX socket. For example:
31517 av_scanner = fsecure:/path/to/.fsav
31519 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
31520 Thelmen for contributing the code for this scanner.
31522 .vitem &%kavdaemon%&
31523 .cindex "virus scanners" "Kaspersky"
31524 This is the scanner daemon of Kaspersky Version 4. This version of the
31525 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
31526 scanner type takes one option, which is the path to the daemon's UNIX socket.
31529 av_scanner = kavdaemon:/opt/AVP/AvpCtl
31531 The default path is &_/var/run/AvpCtl_&.
31534 .cindex "virus scanners" "mksd"
31535 This is a daemon type scanner that is aimed mainly at Polish users, though some
31536 parts of documentation are now available in English. You can get it at
31537 &url(http://linux.mks.com.pl/). The only option for this scanner type is
31538 the maximum number of processes used simultaneously to scan the attachments,
31539 provided that mksd has
31540 been run with at least the same number of child processes. For example:
31542 av_scanner = mksd:2
31544 You can safely omit this option (the default value is 1).
31547 .cindex "virus scanners" "simple socket-connected"
31548 This is a general-purpose way of talking to simple scanner daemons
31549 running on the local machine.
31550 There are four options:
31551 an address (which may be an IP address and port, or the path of a Unix socket),
31552 a commandline to send (may include a single %s which will be replaced with
31553 the path to the mail file to be scanned),
31554 an RE to trigger on from the returned data,
31555 an RE to extract malware_name from the returned data.
31558 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
31560 Default for the socket specifier is &_/tmp/malware.sock_&.
31561 Default for the commandline is &_%s\n_&.
31562 Both regular-expressions are required.
31565 .cindex "virus scanners" "Sophos and Sophie"
31566 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
31567 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
31568 for this scanner type is the path to the UNIX socket that Sophie uses for
31569 client communication. For example:
31571 av_scanner = sophie:/tmp/sophie
31573 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
31577 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
31578 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
31581 The &%av_scanner%& option is expanded each time &%malware%& is called. This
31582 makes it possible to use different scanners. See further below for an example.
31583 The &%malware%& condition caches its results, so when you use it multiple times
31584 for the same message, the actual scanning process is only carried out once.
31585 However, using expandable items in &%av_scanner%& disables this caching, in
31586 which case each use of the &%malware%& condition causes a new scan of the
31589 The &%malware%& condition takes a right-hand argument that is expanded before
31590 use and taken as a list, slash-separated by default.
31591 The first element can then be one of
31594 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
31595 The condition succeeds if a virus was found, and fail otherwise. This is the
31598 &"false"& or &"0"& or an empty string, in which case no scanning is done and
31599 the condition fails immediately.
31601 A regular expression, in which case the message is scanned for viruses. The
31602 condition succeeds if a virus is found and its name matches the regular
31603 expression. This allows you to take special actions on certain types of virus.
31604 Note that &"/"& characters in the RE must be doubled due to the list-processing,
31605 unless the separator is changed (in the usual way).
31608 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
31609 messages even if there is a problem with the virus scanner.
31610 Otherwise, such a problem causes the ACL to defer.
31612 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
31613 specify a non-default timeout. The default is two minutes.
31616 malware = * / defer_ok / tmo=10s
31618 A timeout causes the ACL to defer.
31620 .vindex "&$callout_address$&"
31621 When a connection is made to the scanner the expansion variable &$callout_address$&
31622 is set to record the actual address used.
31624 .vindex "&$malware_name$&"
31625 When a virus is found, the condition sets up an expansion variable called
31626 &$malware_name$& that contains the name of the virus. You can use it in a
31627 &%message%& modifier that specifies the error returned to the sender, and/or in
31630 Beware the interaction of Exim's &%message_size_limit%& with any size limits
31631 imposed by your anti-virus scanner.
31633 Here is a very simple scanning example:
31635 deny message = This message contains malware ($malware_name)
31638 The next example accepts messages when there is a problem with the scanner:
31640 deny message = This message contains malware ($malware_name)
31641 malware = */defer_ok
31643 The next example shows how to use an ACL variable to scan with both sophie and
31644 aveserver. It assumes you have set:
31646 av_scanner = $acl_m0
31648 in the main Exim configuration.
31650 deny message = This message contains malware ($malware_name)
31651 set acl_m0 = sophie
31654 deny message = This message contains malware ($malware_name)
31655 set acl_m0 = aveserver
31660 .section "Scanning with SpamAssassin and Rspamd" "SECTscanspamass"
31661 .cindex "content scanning" "for spam"
31662 .cindex "spam scanning"
31663 .cindex "SpamAssassin"
31665 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
31666 score and a report for the message.
31667 Support is also provided for Rspamd.
31669 For more information about installation and configuration of SpamAssassin or
31670 Rspamd refer to their respective websites at
31671 &url(http://spamassassin.apache.org) and &url(http://www.rspamd.com)
31673 SpamAssassin can be installed with CPAN by running:
31675 perl -MCPAN -e 'install Mail::SpamAssassin'
31677 SpamAssassin has its own set of configuration files. Please review its
31678 documentation to see how you can tweak it. The default installation should work
31681 .oindex "&%spamd_address%&"
31682 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
31683 intend to use an instance running on the local host you do not need to set
31684 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
31685 you must set the &%spamd_address%& option in the global part of the Exim
31686 configuration as follows (example):
31688 spamd_address = 192.168.99.45 387
31690 The SpamAssassin protocol relies on a TCP half-close from the client.
31691 If your SpamAssassin client side is running a Linux system with an
31692 iptables firewall, consider setting
31693 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
31694 timeout, Exim uses when waiting for a response from the SpamAssassin
31695 server (currently defaulting to 120s). With a lower value the Linux
31696 connection tracking may consider your half-closed connection as dead too
31700 To use Rspamd (which by default listens on all local addresses
31702 you should add &%variant=rspamd%& after the address/port pair, for example:
31704 spamd_address = 127.0.0.1 11333 variant=rspamd
31707 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
31708 sockets. If you want to us these, supply &%spamd_address%& with an absolute
31709 file name instead of an address/port pair:
31711 spamd_address = /var/run/spamd_socket
31713 You can have multiple &%spamd%& servers to improve scalability. These can
31714 reside on other hardware reachable over the network. To specify multiple
31715 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
31716 option, separated with colons (the separator can be changed in the usual way):
31718 spamd_address = 192.168.2.10 783 : \
31719 192.168.2.11 783 : \
31722 Up to 32 &%spamd%& servers are supported.
31723 When a server fails to respond to the connection attempt, all other
31724 servers are tried until one succeeds. If no server responds, the &%spam%&
31727 Unix and TCP socket specifications may be mixed in any order.
31728 Each element of the list is a list itself, space-separated by default
31729 and changeable in the usual way; take care to not double the separator.
31731 For TCP socket specifications a host name or IP (v4 or v6, but
31732 subject to list-separator quoting rules) address can be used,
31733 and the port can be one or a dash-separated pair.
31734 In the latter case, the range is tried in strict order.
31736 Elements after the first for Unix sockets, or second for TCP socket,
31738 The supported options are:
31740 pri=<priority> Selection priority
31741 weight=<value> Selection bias
31742 time=<start>-<end> Use only between these times of day
31743 retry=<timespec> Retry on connect fail
31744 tmo=<timespec> Connection time limit
31745 variant=rspamd Use Rspamd rather than SpamAssassin protocol
31748 The &`pri`& option specifies a priority for the server within the list,
31749 higher values being tried first.
31750 The default priority is 1.
31752 The &`weight`& option specifies a selection bias.
31753 Within a priority set
31754 servers are queried in a random fashion, weighted by this value.
31755 The default value for selection bias is 1.
31757 Time specifications for the &`time`& option are <hour>.<minute>.<second>
31758 in the local time zone; each element being one or more digits.
31759 Either the seconds or both minutes and seconds, plus the leading &`.`&
31760 characters, may be omitted and will be taken as zero.
31762 Timeout specifications for the &`retry`& and &`tmo`& options
31763 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
31765 The &`tmo`& option specifies an overall timeout for communication.
31766 The default value is two minutes.
31768 The &`retry`& option specifies a time after which a single retry for
31769 a failed connect is made.
31770 The default is to not retry.
31772 The &%spamd_address%& variable is expanded before use if it starts with
31773 a dollar sign. In this case, the expansion may return a string that is
31774 used as the list so that multiple spamd servers can be the result of an
31777 .vindex "&$callout_address$&"
31778 When a connection is made to the server the expansion variable &$callout_address$&
31779 is set to record the actual address used.
31781 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
31782 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
31784 deny message = This message was classified as SPAM
31787 The right-hand side of the &%spam%& condition specifies a name. This is
31788 relevant if you have set up multiple SpamAssassin profiles. If you do not want
31789 to scan using a specific profile, but rather use the SpamAssassin system-wide
31790 default profile, you can scan for an unknown name, or simply use &"nobody"&.
31791 Rspamd does not use this setting. However, you must put something on the
31794 The name allows you to use per-domain or per-user antispam profiles in
31795 principle, but this is not straightforward in practice, because a message may
31796 have multiple recipients, not necessarily all in the same domain. Because the
31797 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
31798 read the contents of the message, the variables &$local_part$& and &$domain$&
31800 Careful enforcement of single-recipient messages
31801 (e.g. by responding with defer in the recipient ACL for all recipients
31803 or the use of PRDR,
31804 .cindex "PRDR" "use for per-user SpamAssassin profiles"
31805 are needed to use this feature.
31807 The right-hand side of the &%spam%& condition is expanded before being used, so
31808 you can put lookups or conditions there. When the right-hand side evaluates to
31809 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
31812 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
31813 large ones may cause significant performance degradation. As most spam messages
31814 are quite small, it is recommended that you do not scan the big ones. For
31817 deny message = This message was classified as SPAM
31818 condition = ${if < {$message_size}{10K}}
31822 The &%spam%& condition returns true if the threshold specified in the user's
31823 SpamAssassin profile has been matched or exceeded. If you want to use the
31824 &%spam%& condition for its side effects (see the variables below), you can make
31825 it always return &"true"& by appending &`:true`& to the username.
31827 .cindex "spam scanning" "returned variables"
31828 When the &%spam%& condition is run, it sets up a number of expansion
31830 Except for &$spam_report$&,
31831 these variables are saved with the received message so are
31832 available for use at delivery time.
31835 .vitem &$spam_score$&
31836 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
31837 for inclusion in log or reject messages.
31839 .vitem &$spam_score_int$&
31840 The spam score of the message, multiplied by ten, as an integer value. For
31841 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
31842 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
31843 The integer value is useful for numeric comparisons in conditions.
31845 .vitem &$spam_bar$&
31846 A string consisting of a number of &"+"& or &"-"& characters, representing the
31847 integer part of the spam score value. A spam score of 4.4 would have a
31848 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
31849 headers, since MUAs can match on such strings. The maximum length of the
31850 spam bar is 50 characters.
31852 .vitem &$spam_report$&
31853 A multiline text table, containing the full SpamAssassin report for the
31854 message. Useful for inclusion in headers or reject messages.
31855 This variable is only usable in a DATA-time ACL.
31856 Beware that SpamAssassin may return non-ASCII characters, especially
31857 when running in country-specific locales, which are not legal
31858 unencoded in headers.
31860 .vitem &$spam_action$&
31861 For SpamAssassin either 'reject' or 'no action' depending on the
31862 spam score versus threshold.
31863 For Rspamd, the recommended action.
31867 The &%spam%& condition caches its results unless expansion in
31868 spamd_address was used. If you call it again with the same user name, it
31869 does not scan again, but rather returns the same values as before.
31871 The &%spam%& condition returns DEFER if there is any error while running
31872 the message through SpamAssassin or if the expansion of spamd_address
31873 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
31874 statement block), append &`/defer_ok`& to the right-hand side of the
31875 spam condition, like this:
31877 deny message = This message was classified as SPAM
31878 spam = joe/defer_ok
31880 This causes messages to be accepted even if there is a problem with &%spamd%&.
31882 Here is a longer, commented example of the use of the &%spam%&
31885 # put headers in all messages (no matter if spam or not)
31886 warn spam = nobody:true
31887 add_header = X-Spam-Score: $spam_score ($spam_bar)
31888 add_header = X-Spam-Report: $spam_report
31890 # add second subject line with *SPAM* marker when message
31891 # is over threshold
31893 add_header = Subject: *SPAM* $h_Subject:
31895 # reject spam at high scores (> 12)
31896 deny message = This message scored $spam_score spam points.
31898 condition = ${if >{$spam_score_int}{120}{1}{0}}
31903 .section "Scanning MIME parts" "SECTscanmimepart"
31904 .cindex "content scanning" "MIME parts"
31905 .cindex "MIME content scanning"
31906 .oindex "&%acl_smtp_mime%&"
31907 .oindex "&%acl_not_smtp_mime%&"
31908 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
31909 each MIME part of an SMTP message, including multipart types, in the sequence
31910 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
31911 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
31912 options may both refer to the same ACL if you want the same processing in both
31915 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
31916 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
31917 the case of a non-SMTP message. However, a MIME ACL is called only if the
31918 message contains a &'Content-Type:'& header line. When a call to a MIME
31919 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
31920 result code is sent to the client. In the case of an SMTP message, the
31921 &%acl_smtp_data%& ACL is not called when this happens.
31923 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
31924 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
31925 condition to match against the raw MIME part. You can also use the
31926 &%mime_regex%& condition to match against the decoded MIME part (see section
31927 &<<SECTscanregex>>&).
31929 At the start of a MIME ACL, a number of variables are set from the header
31930 information for the relevant MIME part. These are described below. The contents
31931 of the MIME part are not by default decoded into a disk file except for MIME
31932 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
31933 part into a disk file, you can use the &%decode%& condition. The general
31936 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
31938 The right hand side is expanded before use. After expansion,
31942 &"0"& or &"false"&, in which case no decoding is done.
31944 The string &"default"&. In that case, the file is put in the temporary
31945 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
31946 a sequential file name consisting of the message id and a sequence number. The
31947 full path and name is available in &$mime_decoded_filename$& after decoding.
31949 A full path name starting with a slash. If the full name is an existing
31950 directory, it is used as a replacement for the default directory. The filename
31951 is then sequentially assigned. If the path does not exist, it is used as
31952 the full path and file name.
31954 If the string does not start with a slash, it is used as the
31955 filename, and the default path is then used.
31957 The &%decode%& condition normally succeeds. It is only false for syntax
31958 errors or unusual circumstances such as memory shortages. You can easily decode
31959 a file with its original, proposed filename using
31961 decode = $mime_filename
31963 However, you should keep in mind that &$mime_filename$& might contain
31964 anything. If you place files outside of the default path, they are not
31965 automatically unlinked.
31967 For RFC822 attachments (these are messages attached to messages, with a
31968 content-type of &"message/rfc822"&), the ACL is called again in the same manner
31969 as for the primary message, only that the &$mime_is_rfc822$& expansion
31970 variable is set (see below). Attached messages are always decoded to disk
31971 before being checked, and the files are unlinked once the check is done.
31973 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
31974 used to match regular expressions against raw and decoded MIME parts,
31975 respectively. They are described in section &<<SECTscanregex>>&.
31977 .cindex "MIME content scanning" "returned variables"
31978 The following list describes all expansion variables that are
31979 available in the MIME ACL:
31982 .vitem &$mime_boundary$&
31983 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
31984 have a boundary string, which is stored in this variable. If the current part
31985 has no boundary parameter in the &'Content-Type:'& header, this variable
31986 contains the empty string.
31988 .vitem &$mime_charset$&
31989 This variable contains the character set identifier, if one was found in the
31990 &'Content-Type:'& header. Examples for charset identifiers are:
31996 Please note that this value is not normalized, so you should do matches
31997 case-insensitively.
31999 .vitem &$mime_content_description$&
32000 This variable contains the normalized content of the &'Content-Description:'&
32001 header. It can contain a human-readable description of the parts content. Some
32002 implementations repeat the filename for attachments here, but they are usually
32003 only used for display purposes.
32005 .vitem &$mime_content_disposition$&
32006 This variable contains the normalized content of the &'Content-Disposition:'&
32007 header. You can expect strings like &"attachment"& or &"inline"& here.
32009 .vitem &$mime_content_id$&
32010 This variable contains the normalized content of the &'Content-ID:'& header.
32011 This is a unique ID that can be used to reference a part from another part.
32013 .vitem &$mime_content_size$&
32014 This variable is set only after the &%decode%& modifier (see above) has been
32015 successfully run. It contains the size of the decoded part in kilobytes. The
32016 size is always rounded up to full kilobytes, so only a completely empty part
32017 has a &$mime_content_size$& of zero.
32019 .vitem &$mime_content_transfer_encoding$&
32020 This variable contains the normalized content of the
32021 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
32022 type. Typical values are &"base64"& and &"quoted-printable"&.
32024 .vitem &$mime_content_type$&
32025 If the MIME part has a &'Content-Type:'& header, this variable contains its
32026 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
32027 are some examples of popular MIME types, as they may appear in this variable:
32031 application/octet-stream
32035 If the MIME part has no &'Content-Type:'& header, this variable contains the
32038 .vitem &$mime_decoded_filename$&
32039 This variable is set only after the &%decode%& modifier (see above) has been
32040 successfully run. It contains the full path and file name of the file
32041 containing the decoded data.
32046 .vitem &$mime_filename$&
32047 This is perhaps the most important of the MIME variables. It contains a
32048 proposed filename for an attachment, if one was found in either the
32049 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
32052 decoded, but no additional sanity checks are done.
32054 found, this variable contains the empty string.
32056 .vitem &$mime_is_coverletter$&
32057 This variable attempts to differentiate the &"cover letter"& of an e-mail from
32058 attached data. It can be used to clamp down on flashy or unnecessarily encoded
32059 content in the cover letter, while not restricting attachments at all.
32061 The variable contains 1 (true) for a MIME part believed to be part of the
32062 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
32066 The outermost MIME part of a message is always a cover letter.
32069 If a multipart/alternative or multipart/related MIME part is a cover letter,
32070 so are all MIME subparts within that multipart.
32073 If any other multipart is a cover letter, the first subpart is a cover letter,
32074 and the rest are attachments.
32077 All parts contained within an attachment multipart are attachments.
32080 As an example, the following will ban &"HTML mail"& (including that sent with
32081 alternative plain text), while allowing HTML files to be attached. HTML
32082 coverletter mail attached to non-HMTL coverletter mail will also be allowed:
32084 deny message = HTML mail is not accepted here
32085 !condition = $mime_is_rfc822
32086 condition = $mime_is_coverletter
32087 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
32089 .vitem &$mime_is_multipart$&
32090 This variable has the value 1 (true) when the current part has the main type
32091 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
32092 Since multipart entities only serve as containers for other parts, you may not
32093 want to carry out specific actions on them.
32095 .vitem &$mime_is_rfc822$&
32096 This variable has the value 1 (true) if the current part is not a part of the
32097 checked message itself, but part of an attached message. Attached message
32098 decoding is fully recursive.
32100 .vitem &$mime_part_count$&
32101 This variable is a counter that is raised for each processed MIME part. It
32102 starts at zero for the very first part (which is usually a multipart). The
32103 counter is per-message, so it is reset when processing RFC822 attachments (see
32104 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
32105 complete, so you can use it in the DATA ACL to determine the number of MIME
32106 parts of a message. For non-MIME messages, this variable contains the value -1.
32111 .section "Scanning with regular expressions" "SECTscanregex"
32112 .cindex "content scanning" "with regular expressions"
32113 .cindex "regular expressions" "content scanning with"
32114 You can specify your own custom regular expression matches on the full body of
32115 the message, or on individual MIME parts.
32117 The &%regex%& condition takes one or more regular expressions as arguments and
32118 matches them against the full message (when called in the DATA ACL) or a raw
32119 MIME part (when called in the MIME ACL). The &%regex%& condition matches
32120 linewise, with a maximum line length of 32K characters. That means you cannot
32121 have multiline matches with the &%regex%& condition.
32123 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
32124 to 32K of decoded content (the whole content at once, not linewise). If the
32125 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
32126 is decoded automatically when &%mime_regex%& is executed (using default path
32127 and filename values). If the decoded data is larger than 32K, only the first
32128 32K characters are checked.
32130 The regular expressions are passed as a colon-separated list. To include a
32131 literal colon, you must double it. Since the whole right-hand side string is
32132 expanded before being used, you must also escape dollar signs and backslashes
32133 with more backslashes, or use the &`\N`& facility to disable expansion.
32134 Here is a simple example that contains two regular expressions:
32136 deny message = contains blacklisted regex ($regex_match_string)
32137 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
32139 The conditions returns true if any one of the regular expressions matches. The
32140 &$regex_match_string$& expansion variable is then set up and contains the
32141 matching regular expression.
32142 The expansion variables &$regex1$& &$regex2$& etc
32143 are set to any substrings captured by the regular expression.
32145 &*Warning*&: With large messages, these conditions can be fairly
32153 . ////////////////////////////////////////////////////////////////////////////
32154 . ////////////////////////////////////////////////////////////////////////////
32156 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
32157 "Local scan function"
32158 .scindex IIDlosca "&[local_scan()]& function" "description of"
32159 .cindex "customizing" "input scan using C function"
32160 .cindex "policy control" "by local scan function"
32161 In these days of email worms, viruses, and ever-increasing spam, some sites
32162 want to apply a lot of checking to messages before accepting them.
32164 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
32165 passing messages to external virus and spam scanning software. You can also do
32166 a certain amount in Exim itself through string expansions and the &%condition%&
32167 condition in the ACL that runs after the SMTP DATA command or the ACL for
32168 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
32170 To allow for further customization to a site's own requirements, there is the
32171 possibility of linking Exim with a private message scanning function, written
32172 in C. If you want to run code that is written in something other than C, you
32173 can of course use a little C stub to call it.
32175 The local scan function is run once for every incoming message, at the point
32176 when Exim is just about to accept the message.
32177 It can therefore be used to control non-SMTP messages from local processes as
32178 well as messages arriving via SMTP.
32180 Exim applies a timeout to calls of the local scan function, and there is an
32181 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
32182 Zero means &"no timeout"&.
32183 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
32184 before calling the local scan function, so that the most common types of crash
32185 are caught. If the timeout is exceeded or one of those signals is caught, the
32186 incoming message is rejected with a temporary error if it is an SMTP message.
32187 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
32188 code. The incident is logged on the main and reject logs.
32192 .section "Building Exim to use a local scan function" "SECID207"
32193 .cindex "&[local_scan()]& function" "building Exim to use"
32194 To make use of the local scan function feature, you must tell Exim where your
32195 function is before building Exim, by setting LOCAL_SCAN_SOURCE in your
32196 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
32197 directory, so you might set
32199 LOCAL_SCAN_SOURCE=Local/local_scan.c
32201 for example. The function must be called &[local_scan()]&. It is called by
32202 Exim after it has received a message, when the success return code is about to
32203 be sent. This is after all the ACLs have been run. The return code from your
32204 function controls whether the message is actually accepted or not. There is a
32205 commented template function (that just accepts the message) in the file
32206 _src/local_scan.c_.
32208 If you want to make use of Exim's run time configuration file to set options
32209 for your &[local_scan()]& function, you must also set
32211 LOCAL_SCAN_HAS_OPTIONS=yes
32213 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
32218 .section "API for local_scan()" "SECTapiforloc"
32219 .cindex "&[local_scan()]& function" "API description"
32220 You must include this line near the start of your code:
32222 #include "local_scan.h"
32224 This header file defines a number of variables and other values, and the
32225 prototype for the function itself. Exim is coded to use unsigned char values
32226 almost exclusively, and one of the things this header defines is a shorthand
32227 for &`unsigned char`& called &`uschar`&.
32228 It also contains the following macro definitions, to simplify casting character
32229 strings and pointers to character strings:
32231 #define CS (char *)
32232 #define CCS (const char *)
32233 #define CSS (char **)
32234 #define US (unsigned char *)
32235 #define CUS (const unsigned char *)
32236 #define USS (unsigned char **)
32238 The function prototype for &[local_scan()]& is:
32240 extern int local_scan(int fd, uschar **return_text);
32242 The arguments are as follows:
32245 &%fd%& is a file descriptor for the file that contains the body of the message
32246 (the -D file). The file is open for reading and writing, but updating it is not
32247 recommended. &*Warning*&: You must &'not'& close this file descriptor.
32249 The descriptor is positioned at character 19 of the file, which is the first
32250 character of the body itself, because the first 19 characters are the message
32251 id followed by &`-D`& and a newline. If you rewind the file, you should use the
32252 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
32253 case this changes in some future version.
32255 &%return_text%& is an address which you can use to return a pointer to a text
32256 string at the end of the function. The value it points to on entry is NULL.
32259 The function must return an &%int%& value which is one of the following macros:
32262 .vitem &`LOCAL_SCAN_ACCEPT`&
32263 .vindex "&$local_scan_data$&"
32264 The message is accepted. If you pass back a string of text, it is saved with
32265 the message, and made available in the variable &$local_scan_data$&. No
32266 newlines are permitted (if there are any, they are turned into spaces) and the
32267 maximum length of text is 1000 characters.
32269 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
32270 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32271 queued without immediate delivery, and is frozen.
32273 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
32274 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32275 queued without immediate delivery.
32277 .vitem &`LOCAL_SCAN_REJECT`&
32278 The message is rejected; the returned text is used as an error message which is
32279 passed back to the sender and which is also logged. Newlines are permitted &--
32280 they cause a multiline response for SMTP rejections, but are converted to
32281 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
32284 .vitem &`LOCAL_SCAN_TEMPREJECT`&
32285 The message is temporarily rejected; the returned text is used as an error
32286 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
32289 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
32290 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
32291 message is not written to the reject log. It has the effect of unsetting the
32292 &%rejected_header%& log selector for just this rejection. If
32293 &%rejected_header%& is already unset (see the discussion of the
32294 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
32295 same as LOCAL_SCAN_REJECT.
32297 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
32298 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
32299 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
32302 If the message is not being received by interactive SMTP, rejections are
32303 reported by writing to &%stderr%& or by sending an email, as configured by the
32304 &%-oe%& command line options.
32308 .section "Configuration options for local_scan()" "SECTconoptloc"
32309 .cindex "&[local_scan()]& function" "configuration options"
32310 It is possible to have option settings in the main configuration file
32311 that set values in static variables in the &[local_scan()]& module. If you
32312 want to do this, you must have the line
32314 LOCAL_SCAN_HAS_OPTIONS=yes
32316 in your &_Local/Makefile_& when you build Exim. (This line is in
32317 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
32318 file, you must define static variables to hold the option values, and a table
32321 The table must be a vector called &%local_scan_options%&, of type
32322 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
32323 and a pointer to the variable that holds the value. The entries must appear in
32324 alphabetical order. Following &%local_scan_options%& you must also define a
32325 variable called &%local_scan_options_count%& that contains the number of
32326 entries in the table. Here is a short example, showing two kinds of option:
32328 static int my_integer_option = 42;
32329 static uschar *my_string_option = US"a default string";
32331 optionlist local_scan_options[] = {
32332 { "my_integer", opt_int, &my_integer_option },
32333 { "my_string", opt_stringptr, &my_string_option }
32336 int local_scan_options_count =
32337 sizeof(local_scan_options)/sizeof(optionlist);
32339 The values of the variables can now be changed from Exim's runtime
32340 configuration file by including a local scan section as in this example:
32344 my_string = some string of text...
32346 The available types of option data are as follows:
32349 .vitem &*opt_bool*&
32350 This specifies a boolean (true/false) option. The address should point to a
32351 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
32352 that are defined as &"1"& and &"0"&, respectively. If you want to detect
32353 whether such a variable has been set at all, you can initialize it to
32354 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
32357 .vitem &*opt_fixed*&
32358 This specifies a fixed point number, such as is used for load averages.
32359 The address should point to a variable of type &`int`&. The value is stored
32360 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
32363 This specifies an integer; the address should point to a variable of type
32364 &`int`&. The value may be specified in any of the integer formats accepted by
32367 .vitem &*opt_mkint*&
32368 This is the same as &%opt_int%&, except that when such a value is output in a
32369 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
32370 printed with the suffix K or M.
32372 .vitem &*opt_octint*&
32373 This also specifies an integer, but the value is always interpreted as an
32374 octal integer, whether or not it starts with the digit zero, and it is
32375 always output in octal.
32377 .vitem &*opt_stringptr*&
32378 This specifies a string value; the address must be a pointer to a
32379 variable that points to a string (for example, of type &`uschar *`&).
32381 .vitem &*opt_time*&
32382 This specifies a time interval value. The address must point to a variable of
32383 type &`int`&. The value that is placed there is a number of seconds.
32386 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
32387 out the values of all the &[local_scan()]& options.
32391 .section "Available Exim variables" "SECID208"
32392 .cindex "&[local_scan()]& function" "available Exim variables"
32393 The header &_local_scan.h_& gives you access to a number of C variables. These
32394 are the only ones that are guaranteed to be maintained from release to release.
32395 Note, however, that you can obtain the value of any Exim expansion variable,
32396 including &$recipients$&, by calling &'expand_string()'&. The exported
32397 C variables are as follows:
32400 .vitem &*int&~body_linecount*&
32401 This variable contains the number of lines in the message's body.
32403 .vitem &*int&~body_zerocount*&
32404 This variable contains the number of binary zero bytes in the message's body.
32406 .vitem &*unsigned&~int&~debug_selector*&
32407 This variable is set to zero when no debugging is taking place. Otherwise, it
32408 is a bitmap of debugging selectors. Two bits are identified for use in
32409 &[local_scan()]&; they are defined as macros:
32412 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
32413 testing option that is not privileged &-- any caller may set it. All the
32414 other selector bits can be set only by admin users.
32417 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
32418 by the &`+local_scan`& debug selector. It is not included in the default set
32422 Thus, to write to the debugging output only when &`+local_scan`& has been
32423 selected, you should use code like this:
32425 if ((debug_selector & D_local_scan) != 0)
32426 debug_printf("xxx", ...);
32428 .vitem &*uschar&~*expand_string_message*&
32429 After a failing call to &'expand_string()'& (returned value NULL), the
32430 variable &%expand_string_message%& contains the error message, zero-terminated.
32432 .vitem &*header_line&~*header_list*&
32433 A pointer to a chain of header lines. The &%header_line%& structure is
32436 .vitem &*header_line&~*header_last*&
32437 A pointer to the last of the header lines.
32439 .vitem &*uschar&~*headers_charset*&
32440 The value of the &%headers_charset%& configuration option.
32442 .vitem &*BOOL&~host_checking*&
32443 This variable is TRUE during a host checking session that is initiated by the
32444 &%-bh%& command line option.
32446 .vitem &*uschar&~*interface_address*&
32447 The IP address of the interface that received the message, as a string. This
32448 is NULL for locally submitted messages.
32450 .vitem &*int&~interface_port*&
32451 The port on which this message was received. When testing with the &%-bh%&
32452 command line option, the value of this variable is -1 unless a port has been
32453 specified via the &%-oMi%& option.
32455 .vitem &*uschar&~*message_id*&
32456 This variable contains Exim's message id for the incoming message (the value of
32457 &$message_exim_id$&) as a zero-terminated string.
32459 .vitem &*uschar&~*received_protocol*&
32460 The name of the protocol by which the message was received.
32462 .vitem &*int&~recipients_count*&
32463 The number of accepted recipients.
32465 .vitem &*recipient_item&~*recipients_list*&
32466 .cindex "recipient" "adding in local scan"
32467 .cindex "recipient" "removing in local scan"
32468 The list of accepted recipients, held in a vector of length
32469 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
32470 can add additional recipients by calling &'receive_add_recipient()'& (see
32471 below). You can delete recipients by removing them from the vector and
32472 adjusting the value in &%recipients_count%&. In particular, by setting
32473 &%recipients_count%& to zero you remove all recipients. If you then return the
32474 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
32475 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
32476 and then call &'receive_add_recipient()'& as often as needed.
32478 .vitem &*uschar&~*sender_address*&
32479 The envelope sender address. For bounce messages this is the empty string.
32481 .vitem &*uschar&~*sender_host_address*&
32482 The IP address of the sending host, as a string. This is NULL for
32483 locally-submitted messages.
32485 .vitem &*uschar&~*sender_host_authenticated*&
32486 The name of the authentication mechanism that was used, or NULL if the message
32487 was not received over an authenticated SMTP connection.
32489 .vitem &*uschar&~*sender_host_name*&
32490 The name of the sending host, if known.
32492 .vitem &*int&~sender_host_port*&
32493 The port on the sending host.
32495 .vitem &*BOOL&~smtp_input*&
32496 This variable is TRUE for all SMTP input, including BSMTP.
32498 .vitem &*BOOL&~smtp_batched_input*&
32499 This variable is TRUE for BSMTP input.
32501 .vitem &*int&~store_pool*&
32502 The contents of this variable control which pool of memory is used for new
32503 requests. See section &<<SECTmemhanloc>>& for details.
32507 .section "Structure of header lines" "SECID209"
32508 The &%header_line%& structure contains the members listed below.
32509 You can add additional header lines by calling the &'header_add()'& function
32510 (see below). You can cause header lines to be ignored (deleted) by setting
32515 .vitem &*struct&~header_line&~*next*&
32516 A pointer to the next header line, or NULL for the last line.
32518 .vitem &*int&~type*&
32519 A code identifying certain headers that Exim recognizes. The codes are printing
32520 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
32521 Notice in particular that any header line whose type is * is not transmitted
32522 with the message. This flagging is used for header lines that have been
32523 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
32524 lines.) Effectively, * means &"deleted"&.
32526 .vitem &*int&~slen*&
32527 The number of characters in the header line, including the terminating and any
32530 .vitem &*uschar&~*text*&
32531 A pointer to the text of the header. It always ends with a newline, followed by
32532 a zero byte. Internal newlines are preserved.
32537 .section "Structure of recipient items" "SECID210"
32538 The &%recipient_item%& structure contains these members:
32541 .vitem &*uschar&~*address*&
32542 This is a pointer to the recipient address as it was received.
32544 .vitem &*int&~pno*&
32545 This is used in later Exim processing when top level addresses are created by
32546 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
32547 and must always contain -1 at this stage.
32549 .vitem &*uschar&~*errors_to*&
32550 If this value is not NULL, bounce messages caused by failing to deliver to the
32551 recipient are sent to the address it contains. In other words, it overrides the
32552 envelope sender for this one recipient. (Compare the &%errors_to%& generic
32553 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
32554 an unqualified address, Exim qualifies it using the domain from
32555 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
32556 is NULL for all recipients.
32561 .section "Available Exim functions" "SECID211"
32562 .cindex "&[local_scan()]& function" "available Exim functions"
32563 The header &_local_scan.h_& gives you access to a number of Exim functions.
32564 These are the only ones that are guaranteed to be maintained from release to
32568 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
32569 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
32571 This function creates a child process that runs the command specified by
32572 &%argv%&. The environment for the process is specified by &%envp%&, which can
32573 be NULL if no environment variables are to be passed. A new umask is supplied
32574 for the process in &%newumask%&.
32576 Pipes to the standard input and output of the new process are set up
32577 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
32578 standard error is cloned to the standard output. If there are any file
32579 descriptors &"in the way"& in the new process, they are closed. If the final
32580 argument is TRUE, the new process is made into a process group leader.
32582 The function returns the pid of the new process, or -1 if things go wrong.
32584 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
32585 This function waits for a child process to terminate, or for a timeout (in
32586 seconds) to expire. A timeout value of zero means wait as long as it takes. The
32587 return value is as follows:
32592 The process terminated by a normal exit and the value is the process
32598 The process was terminated by a signal and the value is the negation of the
32604 The process timed out.
32608 The was some other error in wait(); &%errno%& is still set.
32611 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
32612 This function provide you with a means of submitting a new message to
32613 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
32614 want, but this packages it all up for you.) The function creates a pipe,
32615 forks a subprocess that is running
32617 exim -t -oem -oi -f <>
32619 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
32620 that is connected to the standard input. The yield of the function is the PID
32621 of the subprocess. You can then write a message to the file descriptor, with
32622 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
32624 When you have finished, call &'child_close()'& to wait for the process to
32625 finish and to collect its ending status. A timeout value of zero is usually
32626 fine in this circumstance. Unless you have made a mistake with the recipient
32627 addresses, you should get a return code of zero.
32630 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
32631 *sender_authentication)*&
32632 This function is a more sophisticated version of &'child_open()'&. The command
32635 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
32637 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
32640 .vitem &*void&~debug_printf(char&~*,&~...)*&
32641 This is Exim's debugging function, with arguments as for &'(printf()'&. The
32642 output is written to the standard error stream. If no debugging is selected,
32643 calls to &'debug_printf()'& have no effect. Normally, you should make calls
32644 conditional on the &`local_scan`& debug selector by coding like this:
32646 if ((debug_selector & D_local_scan) != 0)
32647 debug_printf("xxx", ...);
32650 .vitem &*uschar&~*expand_string(uschar&~*string)*&
32651 This is an interface to Exim's string expansion code. The return value is the
32652 expanded string, or NULL if there was an expansion failure.
32653 The C variable &%expand_string_message%& contains an error message after an
32654 expansion failure. If expansion does not change the string, the return value is
32655 the pointer to the input string. Otherwise, the return value points to a new
32656 block of memory that was obtained by a call to &'store_get()'&. See section
32657 &<<SECTmemhanloc>>& below for a discussion of memory handling.
32659 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
32660 This function allows you to an add additional header line at the end of the
32661 existing ones. The first argument is the type, and should normally be a space
32662 character. The second argument is a format string and any number of
32663 substitution arguments as for &[sprintf()]&. You may include internal newlines
32664 if you want, and you must ensure that the string ends with a newline.
32666 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
32667 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
32668 This function adds a new header line at a specified point in the header
32669 chain. The header itself is specified as for &'header_add()'&.
32671 If &%name%& is NULL, the new header is added at the end of the chain if
32672 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
32673 NULL, the header lines are searched for the first non-deleted header that
32674 matches the name. If one is found, the new header is added before it if
32675 &%after%& is false. If &%after%& is true, the new header is added after the
32676 found header and any adjacent subsequent ones with the same name (even if
32677 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
32678 option controls where the header is added. If it is true, addition is at the
32679 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
32680 headers, or at the top if there are no &'Received:'& headers, you could use
32682 header_add_at_position(TRUE, US"Received", TRUE,
32683 ' ', "X-xxx: ...");
32685 Normally, there is always at least one non-deleted &'Received:'& header, but
32686 there may not be if &%received_header_text%& expands to an empty string.
32689 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
32690 This function removes header lines. If &%occurrence%& is zero or negative, all
32691 occurrences of the header are removed. If occurrence is greater than zero, that
32692 particular instance of the header is removed. If no header(s) can be found that
32693 match the specification, the function does nothing.
32696 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
32697 int&~length,&~BOOL&~notdel)*&"
32698 This function tests whether the given header has the given name. It is not just
32699 a string comparison, because white space is permitted between the name and the
32700 colon. If the &%notdel%& argument is true, a false return is forced for all
32701 &"deleted"& headers; otherwise they are not treated specially. For example:
32703 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
32705 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
32706 .cindex "base64 encoding" "functions for &[local_scan()]& use"
32707 This function base64-encodes a string, which is passed by address and length.
32708 The text may contain bytes of any value, including zero. The result is passed
32709 back in dynamic memory that is obtained by calling &'store_get()'&. It is
32712 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
32713 This function decodes a base64-encoded string. Its arguments are a
32714 zero-terminated base64-encoded string and the address of a variable that is set
32715 to point to the result, which is in dynamic memory. The length of the decoded
32716 string is the yield of the function. If the input is invalid base64 data, the
32717 yield is -1. A zero byte is added to the end of the output string to make it
32718 easy to interpret as a C string (assuming it contains no zeros of its own). The
32719 added zero byte is not included in the returned count.
32721 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
32722 This function checks for a match in a domain list. Domains are always
32723 matched caselessly. The return value is one of the following:
32725 &`OK `& match succeeded
32726 &`FAIL `& match failed
32727 &`DEFER `& match deferred
32729 DEFER is usually caused by some kind of lookup defer, such as the
32730 inability to contact a database.
32732 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
32734 This function checks for a match in a local part list. The third argument
32735 controls case-sensitivity. The return values are as for
32736 &'lss_match_domain()'&.
32738 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
32740 This function checks for a match in an address list. The third argument
32741 controls the case-sensitivity of the local part match. The domain is always
32742 matched caselessly. The return values are as for &'lss_match_domain()'&.
32744 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
32746 This function checks for a match in a host list. The most common usage is
32749 lss_match_host(sender_host_name, sender_host_address, ...)
32751 .vindex "&$sender_host_address$&"
32752 An empty address field matches an empty item in the host list. If the host name
32753 is NULL, the name corresponding to &$sender_host_address$& is automatically
32754 looked up if a host name is required to match an item in the list. The return
32755 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
32756 returns ERROR in the case when it had to look up a host name, but the lookup
32759 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
32761 This function writes to Exim's log files. The first argument should be zero (it
32762 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
32763 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
32764 them. It specifies to which log or logs the message is written. The remaining
32765 arguments are a format and relevant insertion arguments. The string should not
32766 contain any newlines, not even at the end.
32769 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
32770 This function adds an additional recipient to the message. The first argument
32771 is the recipient address. If it is unqualified (has no domain), it is qualified
32772 with the &%qualify_recipient%& domain. The second argument must always be -1.
32774 This function does not allow you to specify a private &%errors_to%& address (as
32775 described with the structure of &%recipient_item%& above), because it pre-dates
32776 the addition of that field to the structure. However, it is easy to add such a
32777 value afterwards. For example:
32779 receive_add_recipient(US"monitor@mydom.example", -1);
32780 recipients_list[recipients_count-1].errors_to =
32781 US"postmaster@mydom.example";
32784 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
32785 This is a convenience function to remove a named recipient from the list of
32786 recipients. It returns true if a recipient was removed, and false if no
32787 matching recipient could be found. The argument must be a complete email
32794 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
32795 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
32796 This function decodes strings that are encoded according to RFC 2047. Typically
32797 these are the contents of header lines. First, each &"encoded word"& is decoded
32798 from the Q or B encoding into a byte-string. Then, if provided with the name of
32799 a charset encoding, and if the &[iconv()]& function is available, an attempt is
32800 made to translate the result to the named character set. If this fails, the
32801 binary string is returned with an error message.
32803 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
32804 maximum MIME word length is enforced. The third argument is the target
32805 encoding, or NULL if no translation is wanted.
32807 .cindex "binary zero" "in RFC 2047 decoding"
32808 .cindex "RFC 2047" "binary zero in"
32809 If a binary zero is encountered in the decoded string, it is replaced by the
32810 contents of the &%zeroval%& argument. For use with Exim headers, the value must
32811 not be 0 because header lines are handled as zero-terminated strings.
32813 The function returns the result of processing the string, zero-terminated; if
32814 &%lenptr%& is not NULL, the length of the result is set in the variable to
32815 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
32817 If an error is encountered, the function returns NULL and uses the &%error%&
32818 argument to return an error message. The variable pointed to by &%error%& is
32819 set to NULL if there is no error; it may be set non-NULL even when the function
32820 returns a non-NULL value if decoding was successful, but there was a problem
32824 .vitem &*int&~smtp_fflush(void)*&
32825 This function is used in conjunction with &'smtp_printf()'&, as described
32828 .vitem &*void&~smtp_printf(char&~*,&~...)*&
32829 The arguments of this function are like &[printf()]&; it writes to the SMTP
32830 output stream. You should use this function only when there is an SMTP output
32831 stream, that is, when the incoming message is being received via interactive
32832 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
32833 is FALSE. If you want to test for an incoming message from another host (as
32834 opposed to a local process that used the &%-bs%& command line option), you can
32835 test the value of &%sender_host_address%&, which is non-NULL when a remote host
32838 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
32839 output function, so it can be used for all forms of SMTP connection.
32841 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
32842 must start with an appropriate response code: 550 if you are going to return
32843 LOCAL_SCAN_REJECT, 451 if you are going to return
32844 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
32845 initial lines of a multi-line response, the code must be followed by a hyphen
32846 to indicate that the line is not the final response line. You must also ensure
32847 that the lines you write terminate with CRLF. For example:
32849 smtp_printf("550-this is some extra info\r\n");
32850 return LOCAL_SCAN_REJECT;
32852 Note that you can also create multi-line responses by including newlines in
32853 the data returned via the &%return_text%& argument. The added value of using
32854 &'smtp_printf()'& is that, for instance, you could introduce delays between
32855 multiple output lines.
32857 The &'smtp_printf()'& function does not return any error indication, because it
32858 does not automatically flush pending output, and therefore does not test
32859 the state of the stream. (In the main code of Exim, flushing and error
32860 detection is done when Exim is ready for the next SMTP input command.) If
32861 you want to flush the output and check for an error (for example, the
32862 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
32863 arguments. It flushes the output stream, and returns a non-zero value if there
32866 .vitem &*void&~*store_get(int)*&
32867 This function accesses Exim's internal store (memory) manager. It gets a new
32868 chunk of memory whose size is given by the argument. Exim bombs out if it ever
32869 runs out of memory. See the next section for a discussion of memory handling.
32871 .vitem &*void&~*store_get_perm(int)*&
32872 This function is like &'store_get()'&, but it always gets memory from the
32873 permanent pool. See the next section for a discussion of memory handling.
32875 .vitem &*uschar&~*string_copy(uschar&~*string)*&
32878 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
32881 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
32882 These three functions create strings using Exim's dynamic memory facilities.
32883 The first makes a copy of an entire string. The second copies up to a maximum
32884 number of characters, indicated by the second argument. The third uses a format
32885 and insertion arguments to create a new string. In each case, the result is a
32886 pointer to a new string in the current memory pool. See the next section for
32892 .section "More about Exim's memory handling" "SECTmemhanloc"
32893 .cindex "&[local_scan()]& function" "memory handling"
32894 No function is provided for freeing memory, because that is never needed.
32895 The dynamic memory that Exim uses when receiving a message is automatically
32896 recycled if another message is received by the same process (this applies only
32897 to incoming SMTP connections &-- other input methods can supply only one
32898 message at a time). After receiving the last message, a reception process
32901 Because it is recycled, the normal dynamic memory cannot be used for holding
32902 data that must be preserved over a number of incoming messages on the same SMTP
32903 connection. However, Exim in fact uses two pools of dynamic memory; the second
32904 one is not recycled, and can be used for this purpose.
32906 If you want to allocate memory that remains available for subsequent messages
32907 in the same SMTP connection, you should set
32909 store_pool = POOL_PERM
32911 before calling the function that does the allocation. There is no need to
32912 restore the value if you do not need to; however, if you do want to revert to
32913 the normal pool, you can either restore the previous value of &%store_pool%& or
32914 set it explicitly to POOL_MAIN.
32916 The pool setting applies to all functions that get dynamic memory, including
32917 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
32918 There is also a convenience function called &'store_get_perm()'& that gets a
32919 block of memory from the permanent pool while preserving the value of
32926 . ////////////////////////////////////////////////////////////////////////////
32927 . ////////////////////////////////////////////////////////////////////////////
32929 .chapter "System-wide message filtering" "CHAPsystemfilter"
32930 .scindex IIDsysfil1 "filter" "system filter"
32931 .scindex IIDsysfil2 "filtering all mail"
32932 .scindex IIDsysfil3 "system filter"
32933 The previous chapters (on ACLs and the local scan function) describe checks
32934 that can be applied to messages before they are accepted by a host. There is
32935 also a mechanism for checking messages once they have been received, but before
32936 they are delivered. This is called the &'system filter'&.
32938 The system filter operates in a similar manner to users' filter files, but it
32939 is run just once per message (however many recipients the message has).
32940 It should not normally be used as a substitute for routing, because &%deliver%&
32941 commands in a system router provide new envelope recipient addresses.
32942 The system filter must be an Exim filter. It cannot be a Sieve filter.
32944 The system filter is run at the start of a delivery attempt, before any routing
32945 is done. If a message fails to be completely delivered at the first attempt,
32946 the system filter is run again at the start of every retry.
32947 If you want your filter to do something only once per message, you can make use
32948 of the &%first_delivery%& condition in an &%if%& command in the filter to
32949 prevent it happening on retries.
32951 .vindex "&$domain$&"
32952 .vindex "&$local_part$&"
32953 &*Warning*&: Because the system filter runs just once, variables that are
32954 specific to individual recipient addresses, such as &$local_part$& and
32955 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
32956 you want to run a centrally-specified filter for each recipient address
32957 independently, you can do so by setting up a suitable &(redirect)& router, as
32958 described in section &<<SECTperaddfil>>& below.
32961 .section "Specifying a system filter" "SECID212"
32962 .cindex "uid (user id)" "system filter"
32963 .cindex "gid (group id)" "system filter"
32964 The name of the file that contains the system filter must be specified by
32965 setting &%system_filter%&. If you want the filter to run under a uid and gid
32966 other than root, you must also set &%system_filter_user%& and
32967 &%system_filter_group%& as appropriate. For example:
32969 system_filter = /etc/mail/exim.filter
32970 system_filter_user = exim
32972 If a system filter generates any deliveries directly to files or pipes (via the
32973 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
32974 specified by setting &%system_filter_file_transport%& and
32975 &%system_filter_pipe_transport%&, respectively. Similarly,
32976 &%system_filter_reply_transport%& must be set to handle any messages generated
32977 by the &%reply%& command.
32980 .section "Testing a system filter" "SECID213"
32981 You can run simple tests of a system filter in the same way as for a user
32982 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
32983 are permitted only in system filters are recognized.
32985 If you want to test the combined effect of a system filter and a user filter,
32986 you can use both &%-bF%& and &%-bf%& on the same command line.
32990 .section "Contents of a system filter" "SECID214"
32991 The language used to specify system filters is the same as for users' filter
32992 files. It is described in the separate end-user document &'Exim's interface to
32993 mail filtering'&. However, there are some additional features that are
32994 available only in system filters; these are described in subsequent sections.
32995 If they are encountered in a user's filter file or when testing with &%-bf%&,
32998 .cindex "frozen messages" "manual thaw; testing in filter"
32999 There are two special conditions which, though available in users' filter
33000 files, are designed for use in system filters. The condition &%first_delivery%&
33001 is true only for the first attempt at delivering a message, and
33002 &%manually_thawed%& is true only if the message has been frozen, and
33003 subsequently thawed by an admin user. An explicit forced delivery counts as a
33004 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
33006 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
33007 specify an &"unseen"& (non-significant) delivery, and that delivery does not
33008 succeed, it will not be tried again.
33009 If you want Exim to retry an unseen delivery until it succeeds, you should
33010 arrange to set it up every time the filter runs.
33012 When a system filter finishes running, the values of the variables &$n0$& &--
33013 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
33014 users' filter files. Thus a system filter can, for example, set up &"scores"&
33015 to which users' filter files can refer.
33019 .section "Additional variable for system filters" "SECID215"
33020 .vindex "&$recipients$&"
33021 The expansion variable &$recipients$&, containing a list of all the recipients
33022 of the message (separated by commas and white space), is available in system
33023 filters. It is not available in users' filters for privacy reasons.
33027 .section "Defer, freeze, and fail commands for system filters" "SECID216"
33028 .cindex "freezing messages"
33029 .cindex "message" "freezing"
33030 .cindex "message" "forced failure"
33031 .cindex "&%fail%&" "in system filter"
33032 .cindex "&%freeze%& in system filter"
33033 .cindex "&%defer%& in system filter"
33034 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
33035 always available in system filters, but are not normally enabled in users'
33036 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
33037 for the &(redirect)& router.) These commands can optionally be followed by the
33038 word &%text%& and a string containing an error message, for example:
33040 fail text "this message looks like spam to me"
33042 The keyword &%text%& is optional if the next character is a double quote.
33044 The &%defer%& command defers delivery of the original recipients of the
33045 message. The &%fail%& command causes all the original recipients to be failed,
33046 and a bounce message to be created. The &%freeze%& command suspends all
33047 delivery attempts for the original recipients. In all cases, any new deliveries
33048 that are specified by the filter are attempted as normal after the filter has
33051 The &%freeze%& command is ignored if the message has been manually unfrozen and
33052 not manually frozen since. This means that automatic freezing by a system
33053 filter can be used as a way of checking out suspicious messages. If a message
33054 is found to be all right, manually unfreezing it allows it to be delivered.
33056 .cindex "log" "&%fail%& command log line"
33057 .cindex "&%fail%&" "log line; reducing"
33058 The text given with a fail command is used as part of the bounce message as
33059 well as being written to the log. If the message is quite long, this can fill
33060 up a lot of log space when such failures are common. To reduce the size of the
33061 log message, Exim interprets the text in a special way if it starts with the
33062 two characters &`<<`& and contains &`>>`& later. The text between these two
33063 strings is written to the log, and the rest of the text is used in the bounce
33064 message. For example:
33066 fail "<<filter test 1>>Your message is rejected \
33067 because it contains attachments that we are \
33068 not prepared to receive."
33071 .cindex "loop" "caused by &%fail%&"
33072 Take great care with the &%fail%& command when basing the decision to fail on
33073 the contents of the message, because the bounce message will of course include
33074 the contents of the original message and will therefore trigger the &%fail%&
33075 command again (causing a mail loop) unless steps are taken to prevent this.
33076 Testing the &%error_message%& condition is one way to prevent this. You could
33079 if $message_body contains "this is spam" and not error_message
33080 then fail text "spam is not wanted here" endif
33082 though of course that might let through unwanted bounce messages. The
33083 alternative is clever checking of the body and/or headers to detect bounces
33084 generated by the filter.
33086 The interpretation of a system filter file ceases after a
33088 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
33089 set up earlier in the filter file are honoured, so you can use a sequence such
33095 to send a specified message when the system filter is freezing (or deferring or
33096 failing) a message. The normal deliveries for the message do not, of course,
33101 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
33102 .cindex "header lines" "adding; in system filter"
33103 .cindex "header lines" "removing; in system filter"
33104 .cindex "filter" "header lines; adding/removing"
33105 Two filter commands that are available only in system filters are:
33107 headers add <string>
33108 headers remove <string>
33110 The argument for the &%headers add%& is a string that is expanded and then
33111 added to the end of the message's headers. It is the responsibility of the
33112 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
33113 space is ignored, and if the string is otherwise empty, or if the expansion is
33114 forced to fail, the command has no effect.
33116 You can use &"\n"& within the string, followed by white space, to specify
33117 continued header lines. More than one header may be added in one command by
33118 including &"\n"& within the string without any following white space. For
33121 headers add "X-header-1: ....\n \
33122 continuation of X-header-1 ...\n\
33125 Note that the header line continuation white space after the first newline must
33126 be placed before the backslash that continues the input string, because white
33127 space after input continuations is ignored.
33129 The argument for &%headers remove%& is a colon-separated list of header names.
33130 This command applies only to those headers that are stored with the message;
33131 those that are added at delivery time (such as &'Envelope-To:'& and
33132 &'Return-Path:'&) cannot be removed by this means. If there is more than one
33133 header with the same name, they are all removed.
33135 The &%headers%& command in a system filter makes an immediate change to the set
33136 of header lines that was received with the message (with possible additions
33137 from ACL processing). Subsequent commands in the system filter operate on the
33138 modified set, which also forms the basis for subsequent message delivery.
33139 Unless further modified during routing or transporting, this set of headers is
33140 used for all recipients of the message.
33142 During routing and transporting, the variables that refer to the contents of
33143 header lines refer only to those lines that are in this set. Thus, header lines
33144 that are added by a system filter are visible to users' filter files and to all
33145 routers and transports. This contrasts with the manipulation of header lines by
33146 routers and transports, which is not immediate, but which instead is saved up
33147 until the message is actually being written (see section
33148 &<<SECTheadersaddrem>>&).
33150 If the message is not delivered at the first attempt, header lines that were
33151 added by the system filter are stored with the message, and so are still
33152 present at the next delivery attempt. Header lines that were removed are still
33153 present, but marked &"deleted"& so that they are not transported with the
33154 message. For this reason, it is usual to make the &%headers%& command
33155 conditional on &%first_delivery%& so that the set of header lines is not
33156 modified more than once.
33158 Because header modification in a system filter acts immediately, you have to
33159 use an indirect approach if you want to modify the contents of a header line.
33162 headers add "Old-Subject: $h_subject:"
33163 headers remove "Subject"
33164 headers add "Subject: new subject (was: $h_old-subject:)"
33165 headers remove "Old-Subject"
33170 .section "Setting an errors address in a system filter" "SECID217"
33171 .cindex "envelope sender"
33172 In a system filter, if a &%deliver%& command is followed by
33174 errors_to <some address>
33176 in order to change the envelope sender (and hence the error reporting) for that
33177 delivery, any address may be specified. (In a user filter, only the current
33178 user's address can be set.) For example, if some mail is being monitored, you
33181 unseen deliver monitor@spying.example errors_to root@local.example
33183 to take a copy which would not be sent back to the normal error reporting
33184 address if its delivery failed.
33188 .section "Per-address filtering" "SECTperaddfil"
33189 .vindex "&$domain$&"
33190 .vindex "&$local_part$&"
33191 In contrast to the system filter, which is run just once per message for each
33192 delivery attempt, it is also possible to set up a system-wide filtering
33193 operation that runs once for each recipient address. In this case, variables
33194 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
33195 filter file could be made dependent on them. This is an example of a router
33196 which implements such a filter:
33201 domains = +local_domains
33202 file = /central/filters/$local_part
33207 The filter is run in a separate process under its own uid. Therefore, either
33208 &%check_local_user%& must be set (as above), in which case the filter is run as
33209 the local user, or the &%user%& option must be used to specify which user to
33210 use. If both are set, &%user%& overrides.
33212 Care should be taken to ensure that none of the commands in the filter file
33213 specify a significant delivery if the message is to go on to be delivered to
33214 its intended recipient. The router will not then claim to have dealt with the
33215 address, so it will be passed on to subsequent routers to be delivered in the
33217 .ecindex IIDsysfil1
33218 .ecindex IIDsysfil2
33219 .ecindex IIDsysfil3
33226 . ////////////////////////////////////////////////////////////////////////////
33227 . ////////////////////////////////////////////////////////////////////////////
33229 .chapter "Message processing" "CHAPmsgproc"
33230 .scindex IIDmesproc "message" "general processing"
33231 Exim performs various transformations on the sender and recipient addresses of
33232 all messages that it handles, and also on the messages' header lines. Some of
33233 these are optional and configurable, while others always take place. All of
33234 this processing, except rewriting as a result of routing, and the addition or
33235 removal of header lines while delivering, happens when a message is received,
33236 before it is placed on Exim's queue.
33238 Some of the automatic processing takes place by default only for
33239 &"locally-originated"& messages. This adjective is used to describe messages
33240 that are not received over TCP/IP, but instead are passed to an Exim process on
33241 its standard input. This includes the interactive &"local SMTP"& case that is
33242 set up by the &%-bs%& command line option.
33244 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
33245 or ::1) are not considered to be locally-originated. Exim does not treat the
33246 loopback interface specially in any way.
33248 If you want the loopback interface to be treated specially, you must ensure
33249 that there are appropriate entries in your ACLs.
33254 .section "Submission mode for non-local messages" "SECTsubmodnon"
33255 .cindex "message" "submission"
33256 .cindex "submission mode"
33257 Processing that happens automatically for locally-originated messages (unless
33258 &%suppress_local_fixups%& is set) can also be requested for messages that are
33259 received over TCP/IP. The term &"submission mode"& is used to describe this
33260 state. Submission mode is set by the modifier
33262 control = submission
33264 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
33265 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
33266 a local submission, and is normally used when the source of the message is
33267 known to be an MUA running on a client host (as opposed to an MTA). For
33268 example, to set submission mode for messages originating on the IPv4 loopback
33269 interface, you could include the following in the MAIL ACL:
33271 warn hosts = 127.0.0.1
33272 control = submission
33274 .cindex "&%sender_retain%& submission option"
33275 There are some options that can be used when setting submission mode. A slash
33276 is used to separate options. For example:
33278 control = submission/sender_retain
33280 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
33281 true and &%local_from_check%& false for the current incoming message. The first
33282 of these allows an existing &'Sender:'& header in the message to remain, and
33283 the second suppresses the check to ensure that &'From:'& matches the
33284 authenticated sender. With this setting, Exim still fixes up messages by adding
33285 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
33286 attempt to check sender authenticity in header lines.
33288 When &%sender_retain%& is not set, a submission mode setting may specify a
33289 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
33292 control = submission/domain=some.domain
33294 The domain may be empty. How this value is used is described in sections
33295 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
33296 that allows you to specify the user's full name for inclusion in a created
33297 &'Sender:'& or &'From:'& header line. For example:
33299 accept authenticated = *
33300 control = submission/domain=wonderland.example/\
33301 name=${lookup {$authenticated_id} \
33302 lsearch {/etc/exim/namelist}}
33304 Because the name may contain any characters, including slashes, the &%name%&
33305 option must be given last. The remainder of the string is used as the name. For
33306 the example above, if &_/etc/exim/namelist_& contains:
33308 bigegg: Humpty Dumpty
33310 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
33313 Sender: Humpty Dumpty <bigegg@wonderland.example>
33315 .cindex "return path" "in submission mode"
33316 By default, submission mode forces the return path to the same address as is
33317 used to create the &'Sender:'& header. However, if &%sender_retain%& is
33318 specified, the return path is also left unchanged.
33320 &*Note*&: The changes caused by submission mode take effect after the predata
33321 ACL. This means that any sender checks performed before the fix-ups use the
33322 untrusted sender address specified by the user, not the trusted sender address
33323 specified by submission mode. Although this might be slightly unexpected, it
33324 does mean that you can configure ACL checks to spot that a user is trying to
33325 spoof another's address.
33327 .section "Line endings" "SECTlineendings"
33328 .cindex "line endings"
33329 .cindex "carriage return"
33331 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
33332 linefeed) is the line ending for messages transmitted over the Internet using
33333 SMTP over TCP/IP. However, within individual operating systems, different
33334 conventions are used. For example, Unix-like systems use just LF, but others
33335 use CRLF or just CR.
33337 Exim was designed for Unix-like systems, and internally, it stores messages
33338 using the system's convention of a single LF as a line terminator. When
33339 receiving a message, all line endings are translated to this standard format.
33340 Originally, it was thought that programs that passed messages directly to an
33341 MTA within an operating system would use that system's convention. Experience
33342 has shown that this is not the case; for example, there are Unix applications
33343 that use CRLF in this circumstance. For this reason, and for compatibility with
33344 other MTAs, the way Exim handles line endings for all messages is now as
33348 LF not preceded by CR is treated as a line ending.
33350 CR is treated as a line ending; if it is immediately followed by LF, the LF
33353 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
33354 nor a local message in the state where a line containing only a dot is a
33357 If a bare CR is encountered within a header line, an extra space is added after
33358 the line terminator so as not to end the header line. The reasoning behind this
33359 is that bare CRs in header lines are most likely either to be mistakes, or
33360 people trying to play silly games.
33362 If the first header line received in a message ends with CRLF, a subsequent
33363 bare LF in a header line is treated in the same way as a bare CR in a header
33371 .section "Unqualified addresses" "SECID218"
33372 .cindex "unqualified addresses"
33373 .cindex "address" "qualification"
33374 By default, Exim expects every envelope address it receives from an external
33375 host to be fully qualified. Unqualified addresses cause negative responses to
33376 SMTP commands. However, because SMTP is used as a means of transporting
33377 messages from MUAs running on personal workstations, there is sometimes a
33378 requirement to accept unqualified addresses from specific hosts or IP networks.
33380 Exim has two options that separately control which hosts may send unqualified
33381 sender or recipient addresses in SMTP commands, namely
33382 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
33383 cases, if an unqualified address is accepted, it is qualified by adding the
33384 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
33386 .oindex "&%qualify_domain%&"
33387 .oindex "&%qualify_recipient%&"
33388 Unqualified addresses in header lines are automatically qualified for messages
33389 that are locally originated, unless the &%-bnq%& option is given on the command
33390 line. For messages received over SMTP, unqualified addresses in header lines
33391 are qualified only if unqualified addresses are permitted in SMTP commands. In
33392 other words, such qualification is also controlled by
33393 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
33398 .section "The UUCP From line" "SECID219"
33399 .cindex "&""From""& line"
33400 .cindex "UUCP" "&""From""& line"
33401 .cindex "sender" "address"
33402 .oindex "&%uucp_from_pattern%&"
33403 .oindex "&%uucp_from_sender%&"
33404 .cindex "envelope sender"
33405 .cindex "Sendmail compatibility" "&""From""& line"
33406 Messages that have come from UUCP (and some other applications) often begin
33407 with a line containing the envelope sender and a timestamp, following the word
33408 &"From"&. Examples of two common formats are:
33410 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
33411 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
33413 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
33414 Exim recognizes such lines at the start of messages that are submitted to it
33415 via the command line (that is, on the standard input). It does not recognize
33416 such lines in incoming SMTP messages, unless the sending host matches
33417 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
33418 and &%ignore_fromline_local%& is set. The recognition is controlled by a
33419 regular expression that is defined by the &%uucp_from_pattern%& option, whose
33420 default value matches the two common cases shown above and puts the address
33421 that follows &"From"& into &$1$&.
33423 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
33424 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
33425 a trusted user, the message's sender address is constructed by expanding the
33426 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
33427 then parsed as an RFC 2822 address. If there is no domain, the local part is
33428 qualified with &%qualify_domain%& unless it is the empty string. However, if
33429 the command line &%-f%& option is used, it overrides the &"From"& line.
33431 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
33432 sender address is not changed. This is also the case for incoming SMTP messages
33433 that are permitted to contain &"From"& lines.
33435 Only one &"From"& line is recognized. If there is more than one, the second is
33436 treated as a data line that starts the body of the message, as it is not valid
33437 as a header line. This also happens if a &"From"& line is present in an
33438 incoming SMTP message from a source that is not permitted to send them.
33442 .section "Resent- header lines" "SECID220"
33443 .cindex "&%Resent-%& header lines"
33444 .cindex "header lines" "Resent-"
33445 RFC 2822 makes provision for sets of header lines starting with the string
33446 &`Resent-`& to be added to a message when it is resent by the original
33447 recipient to somebody else. These headers are &'Resent-Date:'&,
33448 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
33449 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
33452 &'Resent fields are strictly informational. They MUST NOT be used in the normal
33453 processing of replies or other such automatic actions on messages.'&
33456 This leaves things a bit vague as far as other processing actions such as
33457 address rewriting are concerned. Exim treats &%Resent-%& header lines as
33461 A &'Resent-From:'& line that just contains the login id of the submitting user
33462 is automatically rewritten in the same way as &'From:'& (see below).
33464 If there's a rewriting rule for a particular header line, it is also applied to
33465 &%Resent-%& header lines of the same type. For example, a rule that rewrites
33466 &'From:'& also rewrites &'Resent-From:'&.
33468 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
33471 For a locally-submitted message,
33472 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
33473 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
33474 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
33475 included in log lines in this case.
33477 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
33478 &%Resent-%& header lines are present.
33484 .section "The Auto-Submitted: header line" "SECID221"
33485 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
33486 includes the header line:
33488 Auto-Submitted: auto-replied
33491 .section "The Bcc: header line" "SECID222"
33492 .cindex "&'Bcc:'& header line"
33493 If Exim is called with the &%-t%& option, to take recipient addresses from a
33494 message's header, it removes any &'Bcc:'& header line that may exist (after
33495 extracting its addresses). If &%-t%& is not present on the command line, any
33496 existing &'Bcc:'& is not removed.
33499 .section "The Date: header line" "SECID223"
33500 .cindex "&'Date:'& header line"
33501 .cindex "header lines" "Date:"
33502 If a locally-generated or submission-mode message has no &'Date:'& header line,
33503 Exim adds one, using the current date and time, unless the
33504 &%suppress_local_fixups%& control has been specified.
33506 .section "The Delivery-date: header line" "SECID224"
33507 .cindex "&'Delivery-date:'& header line"
33508 .oindex "&%delivery_date_remove%&"
33509 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
33510 set. Exim can be configured to add them to the final delivery of messages. (See
33511 the generic &%delivery_date_add%& transport option.) They should not be present
33512 in messages in transit. If the &%delivery_date_remove%& configuration option is
33513 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
33517 .section "The Envelope-to: header line" "SECID225"
33518 .cindex "&'Envelope-to:'& header line"
33519 .cindex "header lines" "Envelope-to:"
33520 .oindex "&%envelope_to_remove%&"
33521 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
33522 Exim can be configured to add them to the final delivery of messages. (See the
33523 generic &%envelope_to_add%& transport option.) They should not be present in
33524 messages in transit. If the &%envelope_to_remove%& configuration option is set
33525 (the default), Exim removes &'Envelope-to:'& header lines from incoming
33529 .section "The From: header line" "SECTthefrohea"
33530 .cindex "&'From:'& header line"
33531 .cindex "header lines" "From:"
33532 .cindex "Sendmail compatibility" "&""From""& line"
33533 .cindex "message" "submission"
33534 .cindex "submission mode"
33535 If a submission-mode message does not contain a &'From:'& header line, Exim
33536 adds one if either of the following conditions is true:
33539 The envelope sender address is not empty (that is, this is not a bounce
33540 message). The added header line copies the envelope sender address.
33542 .vindex "&$authenticated_id$&"
33543 The SMTP session is authenticated and &$authenticated_id$& is not empty.
33545 .vindex "&$qualify_domain$&"
33546 If no domain is specified by the submission control, the local part is
33547 &$authenticated_id$& and the domain is &$qualify_domain$&.
33549 If a non-empty domain is specified by the submission control, the local
33550 part is &$authenticated_id$&, and the domain is the specified domain.
33552 If an empty domain is specified by the submission control,
33553 &$authenticated_id$& is assumed to be the complete address.
33557 A non-empty envelope sender takes precedence.
33559 If a locally-generated incoming message does not contain a &'From:'& header
33560 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
33561 containing the sender's address. The calling user's login name and full name
33562 are used to construct the address, as described in section &<<SECTconstr>>&.
33563 They are obtained from the password data by calling &[getpwuid()]& (but see the
33564 &%unknown_login%& configuration option). The address is qualified with
33565 &%qualify_domain%&.
33567 For compatibility with Sendmail, if an incoming, non-SMTP message has a
33568 &'From:'& header line containing just the unqualified login name of the calling
33569 user, this is replaced by an address containing the user's login name and full
33570 name as described in section &<<SECTconstr>>&.
33573 .section "The Message-ID: header line" "SECID226"
33574 .cindex "&'Message-ID:'& header line"
33575 .cindex "header lines" "Message-ID:"
33576 .cindex "message" "submission"
33577 .oindex "&%message_id_header_text%&"
33578 If a locally-generated or submission-mode incoming message does not contain a
33579 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
33580 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
33581 to the message. If there are any &'Resent-:'& headers in the message, it
33582 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
33583 message id, preceded by the letter E to ensure it starts with a letter, and
33584 followed by @ and the primary host name. Additional information can be included
33585 in this header line by setting the &%message_id_header_text%& and/or
33586 &%message_id_header_domain%& options.
33589 .section "The Received: header line" "SECID227"
33590 .cindex "&'Received:'& header line"
33591 .cindex "header lines" "Received:"
33592 A &'Received:'& header line is added at the start of every message. The
33593 contents are defined by the &%received_header_text%& configuration option, and
33594 Exim automatically adds a semicolon and a timestamp to the configured string.
33596 The &'Received:'& header is generated as soon as the message's header lines
33597 have been received. At this stage, the timestamp in the &'Received:'& header
33598 line is the time that the message started to be received. This is the value
33599 that is seen by the DATA ACL and by the &[local_scan()]& function.
33601 Once a message is accepted, the timestamp in the &'Received:'& header line is
33602 changed to the time of acceptance, which is (apart from a small delay while the
33603 -H spool file is written) the earliest time at which delivery could start.
33606 .section "The References: header line" "SECID228"
33607 .cindex "&'References:'& header line"
33608 .cindex "header lines" "References:"
33609 Messages created by the &(autoreply)& transport include a &'References:'&
33610 header line. This is constructed according to the rules that are described in
33611 section 3.64 of RFC 2822 (which states that replies should contain such a
33612 header line), and section 3.14 of RFC 3834 (which states that automatic
33613 responses are not different in this respect). However, because some mail
33614 processing software does not cope well with very long header lines, no more
33615 than 12 message IDs are copied from the &'References:'& header line in the
33616 incoming message. If there are more than 12, the first one and then the final
33617 11 are copied, before adding the message ID of the incoming message.
33621 .section "The Return-path: header line" "SECID229"
33622 .cindex "&'Return-path:'& header line"
33623 .cindex "header lines" "Return-path:"
33624 .oindex "&%return_path_remove%&"
33625 &'Return-path:'& header lines are defined as something an MTA may insert when
33626 it does the final delivery of messages. (See the generic &%return_path_add%&
33627 transport option.) Therefore, they should not be present in messages in
33628 transit. If the &%return_path_remove%& configuration option is set (the
33629 default), Exim removes &'Return-path:'& header lines from incoming messages.
33633 .section "The Sender: header line" "SECTthesenhea"
33634 .cindex "&'Sender:'& header line"
33635 .cindex "message" "submission"
33636 .cindex "header lines" "Sender:"
33637 For a locally-originated message from an untrusted user, Exim may remove an
33638 existing &'Sender:'& header line, and it may add a new one. You can modify
33639 these actions by setting the &%local_sender_retain%& option true, the
33640 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
33643 When a local message is received from an untrusted user and
33644 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
33645 control has not been set, a check is made to see if the address given in the
33646 &'From:'& header line is the correct (local) sender of the message. The address
33647 that is expected has the login name as the local part and the value of
33648 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
33649 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
33650 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
33651 line is added to the message.
33653 If you set &%local_from_check%& false, this checking does not occur. However,
33654 the removal of an existing &'Sender:'& line still happens, unless you also set
33655 &%local_sender_retain%& to be true. It is not possible to set both of these
33656 options true at the same time.
33658 .cindex "submission mode"
33659 By default, no processing of &'Sender:'& header lines is done for messages
33660 received over TCP/IP or for messages submitted by trusted users. However, when
33661 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
33662 not specified on the submission control, the following processing takes place:
33664 .vindex "&$authenticated_id$&"
33665 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
33666 authenticated, and &$authenticated_id$& is not empty, a sender address is
33667 created as follows:
33670 .vindex "&$qualify_domain$&"
33671 If no domain is specified by the submission control, the local part is
33672 &$authenticated_id$& and the domain is &$qualify_domain$&.
33674 If a non-empty domain is specified by the submission control, the local part
33675 is &$authenticated_id$&, and the domain is the specified domain.
33677 If an empty domain is specified by the submission control,
33678 &$authenticated_id$& is assumed to be the complete address.
33681 This address is compared with the address in the &'From:'& header line. If they
33682 are different, a &'Sender:'& header line containing the created address is
33683 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
33684 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
33686 .cindex "return path" "created from &'Sender:'&"
33687 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
33688 the message (the envelope sender address) is changed to be the same address,
33689 except in the case of submission mode when &%sender_retain%& is specified.
33693 .section "Adding and removing header lines in routers and transports" &&&
33694 "SECTheadersaddrem"
33695 .cindex "header lines" "adding; in router or transport"
33696 .cindex "header lines" "removing; in router or transport"
33697 When a message is delivered, the addition and removal of header lines can be
33698 specified in a system filter, or on any of the routers and transports that
33699 process the message. Section &<<SECTaddremheasys>>& contains details about
33700 modifying headers in a system filter. Header lines can also be added in an ACL
33701 as a message is received (see section &<<SECTaddheadacl>>&).
33703 In contrast to what happens in a system filter, header modifications that are
33704 specified on routers and transports apply only to the particular recipient
33705 addresses that are being processed by those routers and transports. These
33706 changes do not actually take place until a copy of the message is being
33707 transported. Therefore, they do not affect the basic set of header lines, and
33708 they do not affect the values of the variables that refer to header lines.
33710 &*Note*&: In particular, this means that any expansions in the configuration of
33711 the transport cannot refer to the modified header lines, because such
33712 expansions all occur before the message is actually transported.
33714 For both routers and transports, the argument of a &%headers_add%&
33715 option must be in the form of one or more RFC 2822 header lines, separated by
33716 newlines (coded as &"\n"&). For example:
33718 headers_add = X-added-header: added by $primary_hostname\n\
33719 X-added-second: another added header line
33721 Exim does not check the syntax of these added header lines.
33723 Multiple &%headers_add%& options for a single router or transport can be
33724 specified; the values will append to a single list of header lines.
33725 Each header-line is separately expanded.
33727 The argument of a &%headers_remove%& option must consist of a colon-separated
33728 list of header names. This is confusing, because header names themselves are
33729 often terminated by colons. In this case, the colons are the list separators,
33730 not part of the names. For example:
33732 headers_remove = return-receipt-to:acknowledge-to
33735 Multiple &%headers_remove%& options for a single router or transport can be
33736 specified; the arguments will append to a single header-names list.
33737 Each item is separately expanded.
33738 Note that colons in complex expansions which are used to
33739 form all or part of a &%headers_remove%& list
33740 will act as list separators.
33742 When &%headers_add%& or &%headers_remove%& is specified on a router,
33743 items are expanded at routing time,
33744 and then associated with all addresses that are
33745 accepted by that router, and also with any new addresses that it generates. If
33746 an address passes through several routers as a result of aliasing or
33747 forwarding, the changes are cumulative.
33749 .oindex "&%unseen%&"
33750 However, this does not apply to multiple routers that result from the use of
33751 the &%unseen%& option. Any header modifications that were specified by the
33752 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
33754 Addresses that end up with different &%headers_add%& or &%headers_remove%&
33755 settings cannot be delivered together in a batch, so a transport is always
33756 dealing with a set of addresses that have the same header-processing
33759 The transport starts by writing the original set of header lines that arrived
33760 with the message, possibly modified by the system filter. As it writes out
33761 these lines, it consults the list of header names that were attached to the
33762 recipient address(es) by &%headers_remove%& options in routers, and it also
33763 consults the transport's own &%headers_remove%& option. Header lines whose
33764 names are on either of these lists are not written out. If there are multiple
33765 instances of any listed header, they are all skipped.
33767 After the remaining original header lines have been written, new header
33768 lines that were specified by routers' &%headers_add%& options are written, in
33769 the order in which they were attached to the address. These are followed by any
33770 header lines specified by the transport's &%headers_add%& option.
33772 This way of handling header line modifications in routers and transports has
33773 the following consequences:
33776 The original set of header lines, possibly modified by the system filter,
33777 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
33778 to it, at all times.
33780 Header lines that are added by a router's
33781 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
33782 expansion syntax in subsequent routers or the transport.
33784 Conversely, header lines that are specified for removal by &%headers_remove%&
33785 in a router remain visible to subsequent routers and the transport.
33787 Headers added to an address by &%headers_add%& in a router cannot be removed by
33788 a later router or by a transport.
33790 An added header can refer to the contents of an original header that is to be
33791 removed, even it has the same name as the added header. For example:
33793 headers_remove = subject
33794 headers_add = Subject: new subject (was: $h_subject:)
33798 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
33799 for a &(redirect)& router that has the &%one_time%& option set.
33805 .section "Constructed addresses" "SECTconstr"
33806 .cindex "address" "constructed"
33807 .cindex "constructed address"
33808 When Exim constructs a sender address for a locally-generated message, it uses
33811 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
33815 Zaphod Beeblebrox <zaphod@end.univ.example>
33817 The user name is obtained from the &%-F%& command line option if set, or
33818 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
33819 &"gecos"& field from the password entry. If the &"gecos"& field contains an
33820 ampersand character, this is replaced by the login name with the first letter
33821 upper cased, as is conventional in a number of operating systems. See the
33822 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
33823 The &%unknown_username%& option can be used to specify user names in cases when
33824 there is no password file entry.
33827 In all cases, the user name is made to conform to RFC 2822 by quoting all or
33828 parts of it if necessary. In addition, if it contains any non-printing
33829 characters, it is encoded as described in RFC 2047, which defines a way of
33830 including non-ASCII characters in header lines. The value of the
33831 &%headers_charset%& option specifies the name of the encoding that is used (the
33832 characters are assumed to be in this encoding). The setting of
33833 &%print_topbitchars%& controls whether characters with the top bit set (that
33834 is, with codes greater than 127) count as printing characters or not.
33838 .section "Case of local parts" "SECID230"
33839 .cindex "case of local parts"
33840 .cindex "local part" "case of"
33841 RFC 2822 states that the case of letters in the local parts of addresses cannot
33842 be assumed to be non-significant. Exim preserves the case of local parts of
33843 addresses, but by default it uses a lower-cased form when it is routing,
33844 because on most Unix systems, usernames are in lower case and case-insensitive
33845 routing is required. However, any particular router can be made to use the
33846 original case for local parts by setting the &%caseful_local_part%& generic
33849 .cindex "mixed-case login names"
33850 If you must have mixed-case user names on your system, the best way to proceed,
33851 assuming you want case-independent handling of incoming email, is to set up
33852 your first router to convert incoming local parts in your domains to the
33853 correct case by means of a file lookup. For example:
33857 domains = +local_domains
33858 data = ${lookup{$local_part}cdb\
33859 {/etc/usercased.cdb}{$value}fail}\
33862 For this router, the local part is forced to lower case by the default action
33863 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
33864 up a new local part in the correct case. If you then set &%caseful_local_part%&
33865 on any subsequent routers which process your domains, they will operate on
33866 local parts with the correct case in a case-sensitive manner.
33870 .section "Dots in local parts" "SECID231"
33871 .cindex "dot" "in local part"
33872 .cindex "local part" "dots in"
33873 RFC 2822 forbids empty components in local parts. That is, an unquoted local
33874 part may not begin or end with a dot, nor have two consecutive dots in the
33875 middle. However, it seems that many MTAs do not enforce this, so Exim permits
33876 empty components for compatibility.
33880 .section "Rewriting addresses" "SECID232"
33881 .cindex "rewriting" "addresses"
33882 Rewriting of sender and recipient addresses, and addresses in headers, can
33883 happen automatically, or as the result of configuration options, as described
33884 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
33885 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
33887 Automatic rewriting includes qualification, as mentioned above. The other case
33888 in which it can happen is when an incomplete non-local domain is given. The
33889 routing process may cause this to be expanded into the full domain name. For
33890 example, a header such as
33894 might get rewritten as
33896 To: hare@teaparty.wonderland.fict.example
33898 Rewriting as a result of routing is the one kind of message processing that
33899 does not happen at input time, as it cannot be done until the address has
33902 Strictly, one should not do &'any'& deliveries of a message until all its
33903 addresses have been routed, in case any of the headers get changed as a
33904 result of routing. However, doing this in practice would hold up many
33905 deliveries for unreasonable amounts of time, just because one address could not
33906 immediately be routed. Exim therefore does not delay other deliveries when
33907 routing of one or more addresses is deferred.
33908 .ecindex IIDmesproc
33912 . ////////////////////////////////////////////////////////////////////////////
33913 . ////////////////////////////////////////////////////////////////////////////
33915 .chapter "SMTP processing" "CHAPSMTP"
33916 .scindex IIDsmtpproc1 "SMTP" "processing details"
33917 .scindex IIDsmtpproc2 "LMTP" "processing details"
33918 Exim supports a number of different ways of using the SMTP protocol, and its
33919 LMTP variant, which is an interactive protocol for transferring messages into a
33920 closed mail store application. This chapter contains details of how SMTP is
33921 processed. For incoming mail, the following are available:
33924 SMTP over TCP/IP (Exim daemon or &'inetd'&);
33926 SMTP over the standard input and output (the &%-bs%& option);
33928 Batched SMTP on the standard input (the &%-bS%& option).
33931 For mail delivery, the following are available:
33934 SMTP over TCP/IP (the &(smtp)& transport);
33936 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
33939 LMTP over a pipe to a process running in the local host (the &(lmtp)&
33942 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
33943 the &%use_bsmtp%& option set).
33946 &'Batched SMTP'& is the name for a process in which batches of messages are
33947 stored in or read from files (or pipes), in a format in which SMTP commands are
33948 used to contain the envelope information.
33952 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
33953 .cindex "SMTP" "outgoing over TCP/IP"
33954 .cindex "outgoing SMTP over TCP/IP"
33955 .cindex "LMTP" "over TCP/IP"
33956 .cindex "outgoing LMTP over TCP/IP"
33959 .cindex "SIZE option on MAIL command"
33960 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
33961 The &%protocol%& option selects which protocol is to be used, but the actual
33962 processing is the same in both cases.
33964 If, in response to its EHLO command, Exim is told that the SIZE
33965 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
33966 command. The value of <&'n'&> is the message size plus the value of the
33967 &%size_addition%& option (default 1024) to allow for additions to the message
33968 such as per-transport header lines, or changes made in a
33969 .cindex "transport" "filter"
33970 .cindex "filter" "transport filter"
33971 transport filter. If &%size_addition%& is set negative, the use of SIZE is
33974 If the remote server advertises support for PIPELINING, Exim uses the
33975 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
33976 required for the transaction.
33978 If the remote server advertises support for the STARTTLS command, and Exim
33979 was built to support TLS encryption, it tries to start a TLS session unless the
33980 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
33981 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
33982 is called for verification.
33984 If the remote server advertises support for the AUTH command, Exim scans
33985 the authenticators configuration for any suitable client settings, as described
33986 in chapter &<<CHAPSMTPAUTH>>&.
33988 .cindex "carriage return"
33990 Responses from the remote host are supposed to be terminated by CR followed by
33991 LF. However, there are known to be hosts that do not send CR characters, so in
33992 order to be able to interwork with such hosts, Exim treats LF on its own as a
33995 If a message contains a number of different addresses, all those with the same
33996 characteristics (for example, the same envelope sender) that resolve to the
33997 same set of hosts, in the same order, are sent in a single SMTP transaction,
33998 even if they are for different domains, unless there are more than the setting
33999 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
34000 they are split into groups containing no more than &%max_rcpt%&s addresses
34001 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
34002 in parallel sessions. The order of hosts with identical MX values is not
34003 significant when checking whether addresses can be batched in this way.
34005 When the &(smtp)& transport suffers a temporary failure that is not
34006 message-related, Exim updates its transport-specific database, which contains
34007 records indexed by host name that remember which messages are waiting for each
34008 particular host. It also updates the retry database with new retry times.
34010 .cindex "hints database" "retry keys"
34011 Exim's retry hints are based on host name plus IP address, so if one address of
34012 a multi-homed host is broken, it will soon be skipped most of the time.
34013 See the next section for more detail about error handling.
34015 .cindex "SMTP" "passed connection"
34016 .cindex "SMTP" "batching over TCP/IP"
34017 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
34018 looks in the hints database for the transport to see if there are any queued
34019 messages waiting for the host to which it is connected. If it finds one, it
34020 creates a new Exim process using the &%-MC%& option (which can only be used by
34021 a process running as root or the Exim user) and passes the TCP/IP socket to it
34022 so that it can deliver another message using the same socket. The new process
34023 does only those deliveries that are routed to the connected host, and may in
34024 turn pass the socket on to a third process, and so on.
34026 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
34027 limit the number of messages sent down a single TCP/IP connection.
34029 .cindex "asterisk" "after IP address"
34030 The second and subsequent messages delivered down an existing connection are
34031 identified in the main log by the addition of an asterisk after the closing
34032 square bracket of the IP address.
34037 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
34038 .cindex "error" "in outgoing SMTP"
34039 .cindex "SMTP" "errors in outgoing"
34040 .cindex "host" "error"
34041 Three different kinds of error are recognized for outgoing SMTP: host errors,
34042 message errors, and recipient errors.
34045 .vitem "&*Host errors*&"
34046 A host error is not associated with a particular message or with a
34047 particular recipient of a message. The host errors are:
34050 Connection refused or timed out,
34052 Any error response code on connection,
34054 Any error response code to EHLO or HELO,
34056 Loss of connection at any time, except after &"."&,
34058 I/O errors at any time,
34060 Timeouts during the session, other than in response to MAIL, RCPT or
34061 the &"."& at the end of the data.
34064 For a host error, a permanent error response on connection, or in response to
34065 EHLO, causes all addresses routed to the host to be failed. Any other host
34066 error causes all addresses to be deferred, and retry data to be created for the
34067 host. It is not tried again, for any message, until its retry time arrives. If
34068 the current set of addresses are not all delivered in this run (to some
34069 alternative host), the message is added to the list of those waiting for this
34070 host, so if it is still undelivered when a subsequent successful delivery is
34071 made to the host, it will be sent down the same SMTP connection.
34073 .vitem "&*Message errors*&"
34074 .cindex "message" "error"
34075 A message error is associated with a particular message when sent to a
34076 particular host, but not with a particular recipient of the message. The
34077 message errors are:
34080 Any error response code to MAIL, DATA, or the &"."& that terminates
34083 Timeout after MAIL,
34085 Timeout or loss of connection after the &"."& that terminates the data. A
34086 timeout after the DATA command itself is treated as a host error, as is loss of
34087 connection at any other time.
34090 For a message error, a permanent error response (5&'xx'&) causes all addresses
34091 to be failed, and a delivery error report to be returned to the sender. A
34092 temporary error response (4&'xx'&), or one of the timeouts, causes all
34093 addresses to be deferred. Retry data is not created for the host, but instead,
34094 a retry record for the combination of host plus message id is created. The
34095 message is not added to the list of those waiting for this host. This ensures
34096 that the failing message will not be sent to this host again until the retry
34097 time arrives. However, other messages that are routed to the host are not
34098 affected, so if it is some property of the message that is causing the error,
34099 it will not stop the delivery of other mail.
34101 If the remote host specified support for the SIZE parameter in its response
34102 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
34103 over-large message will cause a message error because the error arrives as a
34106 .vitem "&*Recipient errors*&"
34107 .cindex "recipient" "error"
34108 A recipient error is associated with a particular recipient of a message. The
34109 recipient errors are:
34112 Any error response to RCPT,
34114 Timeout after RCPT.
34117 For a recipient error, a permanent error response (5&'xx'&) causes the
34118 recipient address to be failed, and a bounce message to be returned to the
34119 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
34120 address to be deferred, and routing retry data to be created for it. This is
34121 used to delay processing of the address in subsequent queue runs, until its
34122 routing retry time arrives. This applies to all messages, but because it
34123 operates only in queue runs, one attempt will be made to deliver a new message
34124 to the failing address before the delay starts to operate. This ensures that,
34125 if the failure is really related to the message rather than the recipient
34126 (&"message too big for this recipient"& is a possible example), other messages
34127 have a chance of getting delivered. If a delivery to the address does succeed,
34128 the retry information gets cleared, so all stuck messages get tried again, and
34129 the retry clock is reset.
34131 The message is not added to the list of those waiting for this host. Use of the
34132 host for other messages is unaffected, and except in the case of a timeout,
34133 other recipients are processed independently, and may be successfully delivered
34134 in the current SMTP session. After a timeout it is of course impossible to
34135 proceed with the session, so all addresses get deferred. However, those other
34136 than the one that failed do not suffer any subsequent retry delays. Therefore,
34137 if one recipient is causing trouble, the others have a chance of getting
34138 through when a subsequent delivery attempt occurs before the failing
34139 recipient's retry time.
34142 In all cases, if there are other hosts (or IP addresses) available for the
34143 current set of addresses (for example, from multiple MX records), they are
34144 tried in this run for any undelivered addresses, subject of course to their
34145 own retry data. In other words, recipient error retry data does not take effect
34146 until the next delivery attempt.
34148 Some hosts have been observed to give temporary error responses to every
34149 MAIL command at certain times (&"insufficient space"& has been seen). It
34150 would be nice if such circumstances could be recognized, and defer data for the
34151 host itself created, but this is not possible within the current Exim design.
34152 What actually happens is that retry data for every (host, message) combination
34155 The reason that timeouts after MAIL and RCPT are treated specially is that
34156 these can sometimes arise as a result of the remote host's verification
34157 procedures. Exim makes this assumption, and treats them as if a temporary error
34158 response had been received. A timeout after &"."& is treated specially because
34159 it is known that some broken implementations fail to recognize the end of the
34160 message if the last character of the last line is a binary zero. Thus, it is
34161 helpful to treat this case as a message error.
34163 Timeouts at other times are treated as host errors, assuming a problem with the
34164 host, or the connection to it. If a timeout after MAIL, RCPT,
34165 or &"."& is really a connection problem, the assumption is that at the next try
34166 the timeout is likely to occur at some other point in the dialogue, causing it
34167 then to be treated as a host error.
34169 There is experimental evidence that some MTAs drop the connection after the
34170 terminating &"."& if they do not like the contents of the message for some
34171 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
34172 should be given. That is why Exim treats this case as a message rather than a
34173 host error, in order not to delay other messages to the same host.
34178 .section "Incoming SMTP messages over TCP/IP" "SECID233"
34179 .cindex "SMTP" "incoming over TCP/IP"
34180 .cindex "incoming SMTP over TCP/IP"
34183 Incoming SMTP messages can be accepted in one of two ways: by running a
34184 listening daemon, or by using &'inetd'&. In the latter case, the entry in
34185 &_/etc/inetd.conf_& should be like this:
34187 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
34189 Exim distinguishes between this case and the case of a locally running user
34190 agent using the &%-bs%& option by checking whether or not the standard input is
34191 a socket. When it is, either the port must be privileged (less than 1024), or
34192 the caller must be root or the Exim user. If any other user passes a socket
34193 with an unprivileged port number, Exim prints a message on the standard error
34194 stream and exits with an error code.
34196 By default, Exim does not make a log entry when a remote host connects or
34197 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
34198 unexpected. It can be made to write such log entries by setting the
34199 &%smtp_connection%& log selector.
34201 .cindex "carriage return"
34203 Commands from the remote host are supposed to be terminated by CR followed by
34204 LF. However, there are known to be hosts that do not send CR characters. In
34205 order to be able to interwork with such hosts, Exim treats LF on its own as a
34207 Furthermore, because common code is used for receiving messages from all
34208 sources, a CR on its own is also interpreted as a line terminator. However, the
34209 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
34211 .cindex "EHLO" "invalid data"
34212 .cindex "HELO" "invalid data"
34213 One area that sometimes gives rise to problems concerns the EHLO or
34214 HELO commands. Some clients send syntactically invalid versions of these
34215 commands, which Exim rejects by default. (This is nothing to do with verifying
34216 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
34217 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
34218 match the broken hosts that send invalid commands.
34220 .cindex "SIZE option on MAIL command"
34221 .cindex "MAIL" "SIZE option"
34222 The amount of disk space available is checked whenever SIZE is received on
34223 a MAIL command, independently of whether &%message_size_limit%& or
34224 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
34225 false. A temporary error is given if there is not enough space. If
34226 &%check_spool_space%& is set, the check is for that amount of space plus the
34227 value given with SIZE, that is, it checks that the addition of the incoming
34228 message will not reduce the space below the threshold.
34230 When a message is successfully received, Exim includes the local message id in
34231 its response to the final &"."& that terminates the data. If the remote host
34232 logs this text it can help with tracing what has happened to a message.
34234 The Exim daemon can limit the number of simultaneous incoming connections it is
34235 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
34236 number of simultaneous incoming connections from a single remote host (see the
34237 &%smtp_accept_max_per_host%& option). Additional connection attempts are
34238 rejected using the SMTP temporary error code 421.
34240 The Exim daemon does not rely on the SIGCHLD signal to detect when a
34241 subprocess has finished, as this can get lost at busy times. Instead, it looks
34242 for completed subprocesses every time it wakes up. Provided there are other
34243 things happening (new incoming calls, starts of queue runs), completed
34244 processes will be noticed and tidied away. On very quiet systems you may
34245 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
34246 it will be noticed when the daemon next wakes up.
34248 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
34249 and can also be set up to reject SMTP calls from non-reserved hosts at times of
34250 high system load &-- for details see the &%smtp_accept_reserve%&,
34251 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
34252 applies in both the daemon and &'inetd'& cases.
34254 Exim normally starts a delivery process for each message received, though this
34255 can be varied by means of the &%-odq%& command line option and the
34256 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
34257 number of simultaneously running delivery processes started in this way from
34258 SMTP input can be limited by the &%smtp_accept_queue%& and
34259 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
34260 subsequently received messages are just put on the input queue without starting
34261 a delivery process.
34263 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
34264 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
34265 started up from the &'inetd'& daemon, because in that case each connection is
34266 handled by an entirely independent Exim process. Control by load average is,
34267 however, available with &'inetd'&.
34269 Exim can be configured to verify addresses in incoming SMTP commands as they
34270 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
34271 to rewrite addresses at this time &-- before any syntax checking is done. See
34272 section &<<SECTrewriteS>>&.
34274 Exim can also be configured to limit the rate at which a client host submits
34275 MAIL and RCPT commands in a single SMTP session. See the
34276 &%smtp_ratelimit_hosts%& option.
34280 .section "Unrecognized SMTP commands" "SECID234"
34281 .cindex "SMTP" "unrecognized commands"
34282 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
34283 commands during a single SMTP connection, it drops the connection after sending
34284 the error response to the last command. The default value for
34285 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
34286 abuse that subvert web servers into making connections to SMTP ports; in these
34287 circumstances, a number of non-SMTP lines are sent first.
34290 .section "Syntax and protocol errors in SMTP commands" "SECID235"
34291 .cindex "SMTP" "syntax errors"
34292 .cindex "SMTP" "protocol errors"
34293 A syntax error is detected if an SMTP command is recognized, but there is
34294 something syntactically wrong with its data, for example, a malformed email
34295 address in a RCPT command. Protocol errors include invalid command
34296 sequencing such as RCPT before MAIL. If Exim receives more than
34297 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
34298 drops the connection after sending the error response to the last command. The
34299 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
34300 broken clients that loop sending bad commands (yes, it has been seen).
34304 .section "Use of non-mail SMTP commands" "SECID236"
34305 .cindex "SMTP" "non-mail commands"
34306 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
34307 DATA. Exim counts such commands, and drops the connection if there are too
34308 many of them in a single SMTP session. This action catches some
34309 denial-of-service attempts and things like repeated failing AUTHs, or a mad
34310 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
34311 defines what &"too many"& means. Its default value is 10.
34313 When a new message is expected, one occurrence of RSET is not counted. This
34314 allows a client to send one RSET between messages (this is not necessary,
34315 but some clients do it). Exim also allows one uncounted occurrence of HELO
34316 or EHLO, and one occurrence of STARTTLS between messages. After
34317 starting up a TLS session, another EHLO is expected, and so it too is not
34320 The first occurrence of AUTH in a connection, or immediately following
34321 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
34322 RCPT, DATA, and QUIT are counted.
34324 You can control which hosts are subject to the limit set by
34325 &%smtp_accept_max_nonmail%& by setting
34326 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
34327 the limit apply to all hosts. This option means that you can exclude any
34328 specific badly-behaved hosts that you have to live with.
34333 .section "The VRFY and EXPN commands" "SECID237"
34334 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
34335 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
34336 appropriate) in order to decide whether the command should be accepted or not.
34338 .cindex "VRFY" "processing"
34339 When no ACL is defined for VRFY, or if it rejects without
34340 setting an explicit response code, the command is accepted
34341 (with a 252 SMTP response code)
34342 in order to support awkward clients that do a VRFY before every RCPT.
34343 When VRFY is accepted, it runs exactly the same code as when Exim is
34344 called with the &%-bv%& option, and returns 250/451/550
34345 SMTP response codes.
34347 .cindex "EXPN" "processing"
34348 If no ACL for EXPN is defined, the command is rejected.
34349 When EXPN is accepted, a single-level expansion of the address is done.
34350 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
34351 than a verification (the &%-bv%& option). If an unqualified local part is given
34352 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
34353 of VRFY and EXPN commands are logged on the main and reject logs, and
34354 VRFY verification failures are logged on the main log for consistency with
34359 .section "The ETRN command" "SECTETRN"
34360 .cindex "ETRN" "processing"
34361 RFC 1985 describes an SMTP command called ETRN that is designed to
34362 overcome the security problems of the TURN command (which has fallen into
34363 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
34364 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
34365 should be accepted or not. If no ACL is defined, the command is rejected.
34367 The ETRN command is concerned with &"releasing"& messages that are awaiting
34368 delivery to certain hosts. As Exim does not organize its message queue by host,
34369 the only form of ETRN that is supported by default is the one where the
34370 text starts with the &"#"& prefix, in which case the remainder of the text is
34371 specific to the SMTP server. A valid ETRN command causes a run of Exim with
34372 the &%-R%& option to happen, with the remainder of the ETRN text as its
34373 argument. For example,
34381 which causes a delivery attempt on all messages with undelivered addresses
34382 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
34383 default), Exim prevents the simultaneous execution of more than one queue run
34384 for the same argument string as a result of an ETRN command. This stops
34385 a misbehaving client from starting more than one queue runner at once.
34387 .cindex "hints database" "ETRN serialization"
34388 Exim implements the serialization by means of a hints database in which a
34389 record is written whenever a process is started by ETRN, and deleted when
34390 the process completes. However, Exim does not keep the SMTP session waiting for
34391 the ETRN process to complete. Once ETRN is accepted, the client is sent
34392 a &"success"& return code. Obviously there is scope for hints records to get
34393 left lying around if there is a system or program crash. To guard against this,
34394 Exim ignores any records that are more than six hours old.
34396 .oindex "&%smtp_etrn_command%&"
34397 For more control over what ETRN does, the &%smtp_etrn_command%& option can
34398 used. This specifies a command that is run whenever ETRN is received,
34399 whatever the form of its argument. For
34402 smtp_etrn_command = /etc/etrn_command $domain \
34403 $sender_host_address
34405 .vindex "&$domain$&"
34406 The string is split up into arguments which are independently expanded. The
34407 expansion variable &$domain$& is set to the argument of the ETRN command,
34408 and no syntax checking is done on the contents of this argument. Exim does not
34409 wait for the command to complete, so its status code is not checked. Exim runs
34410 under its own uid and gid when receiving incoming SMTP, so it is not possible
34411 for it to change them before running the command.
34415 .section "Incoming local SMTP" "SECID238"
34416 .cindex "SMTP" "local incoming"
34417 Some user agents use SMTP to pass messages to their local MTA using the
34418 standard input and output, as opposed to passing the envelope on the command
34419 line and writing the message to the standard input. This is supported by the
34420 &%-bs%& option. This form of SMTP is handled in the same way as incoming
34421 messages over TCP/IP (including the use of ACLs), except that the envelope
34422 sender given in a MAIL command is ignored unless the caller is trusted. In
34423 an ACL you can detect this form of SMTP input by testing for an empty host
34424 identification. It is common to have this as the first line in the ACL that
34425 runs for RCPT commands:
34429 This accepts SMTP messages from local processes without doing any other tests.
34433 .section "Outgoing batched SMTP" "SECTbatchSMTP"
34434 .cindex "SMTP" "batched outgoing"
34435 .cindex "batched SMTP output"
34436 Both the &(appendfile)& and &(pipe)& transports can be used for handling
34437 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
34438 be output in BSMTP format. No SMTP responses are possible for this form of
34439 delivery. All it is doing is using SMTP commands as a way of transmitting the
34440 envelope along with the message.
34442 The message is written to the file or pipe preceded by the SMTP commands
34443 MAIL and RCPT, and followed by a line containing a single dot. Lines in
34444 the message that start with a dot have an extra dot added. The SMTP command
34445 HELO is not normally used. If it is required, the &%message_prefix%& option
34446 can be used to specify it.
34448 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
34449 one recipient address at a time by default. However, you can arrange for them
34450 to handle several addresses at once by setting the &%batch_max%& option. When
34451 this is done for BSMTP, messages may contain multiple RCPT commands. See
34452 chapter &<<CHAPbatching>>& for more details.
34455 When one or more addresses are routed to a BSMTP transport by a router that
34456 sets up a host list, the name of the first host on the list is available to the
34457 transport in the variable &$host$&. Here is an example of such a transport and
34462 driver = manualroute
34463 transport = smtp_appendfile
34464 route_list = domain.example batch.host.example
34468 driver = appendfile
34469 directory = /var/bsmtp/$host
34474 This causes messages addressed to &'domain.example'& to be written in BSMTP
34475 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
34476 message (unless there are more than 1000 recipients).
34480 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
34481 .cindex "SMTP" "batched incoming"
34482 .cindex "batched SMTP input"
34483 The &%-bS%& command line option causes Exim to accept one or more messages by
34484 reading SMTP on the standard input, but to generate no responses. If the caller
34485 is trusted, the senders in the MAIL commands are believed; otherwise the
34486 sender is always the caller of Exim. Unqualified senders and receivers are not
34487 rejected (there seems little point) but instead just get qualified. HELO
34488 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
34489 as NOOP; QUIT quits.
34491 Minimal policy checking is done for BSMTP input. Only the non-SMTP
34492 ACL is run in the same way as for non-SMTP local input.
34494 If an error is detected while reading a message, including a missing &"."& at
34495 the end, Exim gives up immediately. It writes details of the error to the
34496 standard output in a stylized way that the calling program should be able to
34497 make some use of automatically, for example:
34499 554 Unexpected end of file
34500 Transaction started in line 10
34501 Error detected in line 14
34503 It writes a more verbose version, for human consumption, to the standard error
34506 An error was detected while processing a file of BSMTP input.
34507 The error message was:
34509 501 '>' missing at end of address
34511 The SMTP transaction started in line 10.
34512 The error was detected in line 12.
34513 The SMTP command at fault was:
34515 rcpt to:<malformed@in.com.plete
34517 1 previous message was successfully processed.
34518 The rest of the batch was abandoned.
34520 The return code from Exim is zero only if there were no errors. It is 1 if some
34521 messages were accepted before an error was detected, and 2 if no messages were
34523 .ecindex IIDsmtpproc1
34524 .ecindex IIDsmtpproc2
34528 . ////////////////////////////////////////////////////////////////////////////
34529 . ////////////////////////////////////////////////////////////////////////////
34531 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
34532 "Customizing messages"
34533 When a message fails to be delivered, or remains on the queue for more than a
34534 configured amount of time, Exim sends a message to the original sender, or
34535 to an alternative configured address. The text of these messages is built into
34536 the code of Exim, but it is possible to change it, either by adding a single
34537 string, or by replacing each of the paragraphs by text supplied in a file.
34539 The &'From:'& and &'To:'& header lines are automatically generated; you can
34540 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
34541 option. Exim also adds the line
34543 Auto-Submitted: auto-generated
34545 to all warning and bounce messages,
34548 .section "Customizing bounce messages" "SECID239"
34549 .cindex "customizing" "bounce message"
34550 .cindex "bounce message" "customizing"
34551 If &%bounce_message_text%& is set, its contents are included in the default
34552 message immediately after &"This message was created automatically by mail
34553 delivery software."& The string is not expanded. It is not used if
34554 &%bounce_message_file%& is set.
34556 When &%bounce_message_file%& is set, it must point to a template file for
34557 constructing error messages. The file consists of a series of text items,
34558 separated by lines consisting of exactly four asterisks. If the file cannot be
34559 opened, default text is used and a message is written to the main and panic
34560 logs. If any text item in the file is empty, default text is used for that
34563 .vindex "&$bounce_recipient$&"
34564 .vindex "&$bounce_return_size_limit$&"
34565 Each item of text that is read from the file is expanded, and there are two
34566 expansion variables which can be of use here: &$bounce_recipient$& is set to
34567 the recipient of an error message while it is being created, and
34568 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
34569 option, rounded to a whole number.
34571 The items must appear in the file in the following order:
34574 The first item is included in the headers, and should include at least a
34575 &'Subject:'& header. Exim does not check the syntax of these headers.
34577 The second item forms the start of the error message. After it, Exim lists the
34578 failing addresses with their error messages.
34580 The third item is used to introduce any text from pipe transports that is to be
34581 returned to the sender. It is omitted if there is no such text.
34583 The fourth, fifth and sixth items will be ignored and may be empty.
34584 The fields exist for back-compatibility
34587 The default state (&%bounce_message_file%& unset) is equivalent to the
34588 following file, in which the sixth item is empty. The &'Subject:'& and some
34589 other lines have been split in order to fit them on the page:
34591 Subject: Mail delivery failed
34592 ${if eq{$sender_address}{$bounce_recipient}
34593 {: returning message to sender}}
34595 This message was created automatically by mail delivery software.
34597 A message ${if eq{$sender_address}{$bounce_recipient}
34598 {that you sent }{sent by
34602 }}could not be delivered to all of its recipients.
34603 This is a permanent error. The following address(es) failed:
34605 The following text was generated during the delivery attempt(s):
34607 ------ This is a copy of the message, including all the headers.
34610 ------ The body of the message is $message_size characters long;
34612 ------ $bounce_return_size_limit or so are included here.
34615 .section "Customizing warning messages" "SECTcustwarn"
34616 .cindex "customizing" "warning message"
34617 .cindex "warning of delay" "customizing the message"
34618 The option &%warn_message_file%& can be pointed at a template file for use when
34619 warnings about message delays are created. In this case there are only three
34623 The first item is included in the headers, and should include at least a
34624 &'Subject:'& header. Exim does not check the syntax of these headers.
34626 The second item forms the start of the warning message. After it, Exim lists
34627 the delayed addresses.
34629 The third item then ends the message.
34632 The default state is equivalent to the following file, except that some lines
34633 have been split here, in order to fit them on the page:
34635 Subject: Warning: message $message_exim_id delayed
34636 $warn_message_delay
34638 This message was created automatically by mail delivery software.
34640 A message ${if eq{$sender_address}{$warn_message_recipients}
34641 {that you sent }{sent by
34645 }}has not been delivered to all of its recipients after
34646 more than $warn_message_delay on the queue on $primary_hostname.
34648 The message identifier is: $message_exim_id
34649 The subject of the message is: $h_subject
34650 The date of the message is: $h_date
34652 The following address(es) have not yet been delivered:
34654 No action is required on your part. Delivery attempts will
34655 continue for some time, and this warning may be repeated at
34656 intervals if the message remains undelivered. Eventually the
34657 mail delivery software will give up, and when that happens,
34658 the message will be returned to you.
34660 .vindex "&$warn_message_delay$&"
34661 .vindex "&$warn_message_recipients$&"
34662 However, in the default state the subject and date lines are omitted if no
34663 appropriate headers exist. During the expansion of this file,
34664 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
34665 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
34666 of recipients for the warning message. There may be more than one if there are
34667 multiple addresses with different &%errors_to%& settings on the routers that
34673 . ////////////////////////////////////////////////////////////////////////////
34674 . ////////////////////////////////////////////////////////////////////////////
34676 .chapter "Some common configuration settings" "CHAPcomconreq"
34677 This chapter discusses some configuration settings that seem to be fairly
34678 common. More examples and discussion can be found in the Exim book.
34682 .section "Sending mail to a smart host" "SECID240"
34683 .cindex "smart host" "example router"
34684 If you want to send all mail for non-local domains to a &"smart host"&, you
34685 should replace the default &(dnslookup)& router with a router which does the
34686 routing explicitly:
34688 send_to_smart_host:
34689 driver = manualroute
34690 route_list = !+local_domains smart.host.name
34691 transport = remote_smtp
34693 You can use the smart host's IP address instead of the name if you wish.
34694 If you are using Exim only to submit messages to a smart host, and not for
34695 receiving incoming messages, you can arrange for it to do the submission
34696 synchronously by setting the &%mua_wrapper%& option (see chapter
34697 &<<CHAPnonqueueing>>&).
34702 .section "Using Exim to handle mailing lists" "SECTmailinglists"
34703 .cindex "mailing lists"
34704 Exim can be used to run simple mailing lists, but for large and/or complicated
34705 requirements, the use of additional specialized mailing list software such as
34706 Majordomo or Mailman is recommended.
34708 The &(redirect)& router can be used to handle mailing lists where each list
34709 is maintained in a separate file, which can therefore be managed by an
34710 independent manager. The &%domains%& router option can be used to run these
34711 lists in a separate domain from normal mail. For example:
34715 domains = lists.example
34716 file = /usr/lists/$local_part
34719 errors_to = $local_part-request@lists.example
34722 This router is skipped for domains other than &'lists.example'&. For addresses
34723 in that domain, it looks for a file that matches the local part. If there is no
34724 such file, the router declines, but because &%no_more%& is set, no subsequent
34725 routers are tried, and so the whole delivery fails.
34727 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
34728 expanded into a file name or a pipe delivery, which is usually inappropriate in
34731 .oindex "&%errors_to%&"
34732 The &%errors_to%& option specifies that any delivery errors caused by addresses
34733 taken from a mailing list are to be sent to the given address rather than the
34734 original sender of the message. However, before acting on this, Exim verifies
34735 the error address, and ignores it if verification fails.
34737 For example, using the configuration above, mail sent to
34738 &'dicts@lists.example'& is passed on to those addresses contained in
34739 &_/usr/lists/dicts_&, with error reports directed to
34740 &'dicts-request@lists.example'&, provided that this address can be verified.
34741 There could be a file called &_/usr/lists/dicts-request_& containing
34742 the address(es) of this particular list's manager(s), but other approaches,
34743 such as setting up an earlier router (possibly using the &%local_part_prefix%&
34744 or &%local_part_suffix%& options) to handle addresses of the form
34745 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
34749 .section "Syntax errors in mailing lists" "SECID241"
34750 .cindex "mailing lists" "syntax errors in"
34751 If an entry in redirection data contains a syntax error, Exim normally defers
34752 delivery of the original address. That means that a syntax error in a mailing
34753 list holds up all deliveries to the list. This may not be appropriate when a
34754 list is being maintained automatically from data supplied by users, and the
34755 addresses are not rigorously checked.
34757 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
34758 entries that fail to parse, noting the incident in the log. If in addition
34759 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
34760 whenever a broken address is skipped. It is usually appropriate to set
34761 &%syntax_errors_to%& to the same address as &%errors_to%&.
34765 .section "Re-expansion of mailing lists" "SECID242"
34766 .cindex "mailing lists" "re-expansion of"
34767 Exim remembers every individual address to which a message has been delivered,
34768 in order to avoid duplication, but it normally stores only the original
34769 recipient addresses with a message. If all the deliveries to a mailing list
34770 cannot be done at the first attempt, the mailing list is re-expanded when the
34771 delivery is next tried. This means that alterations to the list are taken into
34772 account at each delivery attempt, so addresses that have been added to
34773 the list since the message arrived will therefore receive a copy of the
34774 message, even though it pre-dates their subscription.
34776 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
34777 on the &(redirect)& router. If this is done, any addresses generated by the
34778 router that fail to deliver at the first attempt are added to the message as
34779 &"top level"& addresses, and the parent address that generated them is marked
34780 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
34781 subsequent delivery attempts. The disadvantage of this is that if any of the
34782 failing addresses are incorrect, correcting them in the file has no effect on
34783 pre-existing messages.
34785 The original top-level address is remembered with each of the generated
34786 addresses, and is output in any log messages. However, any intermediate parent
34787 addresses are not recorded. This makes a difference to the log only if the
34788 &%all_parents%& selector is set, but for mailing lists there is normally only
34789 one level of expansion anyway.
34793 .section "Closed mailing lists" "SECID243"
34794 .cindex "mailing lists" "closed"
34795 The examples so far have assumed open mailing lists, to which anybody may
34796 send mail. It is also possible to set up closed lists, where mail is accepted
34797 from specified senders only. This is done by making use of the generic
34798 &%senders%& option to restrict the router that handles the list.
34800 The following example uses the same file as a list of recipients and as a list
34801 of permitted senders. It requires three routers:
34805 domains = lists.example
34806 local_part_suffix = -request
34807 file = /usr/lists/$local_part$local_part_suffix
34812 domains = lists.example
34813 senders = ${if exists {/usr/lists/$local_part}\
34814 {lsearch;/usr/lists/$local_part}{*}}
34815 file = /usr/lists/$local_part
34818 errors_to = $local_part-request@lists.example
34823 domains = lists.example
34825 data = :fail: $local_part@lists.example is a closed mailing list
34827 All three routers have the same &%domains%& setting, so for any other domains,
34828 they are all skipped. The first router runs only if the local part ends in
34829 &%-request%&. It handles messages to the list manager(s) by means of an open
34832 The second router runs only if the &%senders%& precondition is satisfied. It
34833 checks for the existence of a list that corresponds to the local part, and then
34834 checks that the sender is on the list by means of a linear search. It is
34835 necessary to check for the existence of the file before trying to search it,
34836 because otherwise Exim thinks there is a configuration error. If the file does
34837 not exist, the expansion of &%senders%& is *, which matches all senders. This
34838 means that the router runs, but because there is no list, declines, and
34839 &%no_more%& ensures that no further routers are run. The address fails with an
34840 &"unrouteable address"& error.
34842 The third router runs only if the second router is skipped, which happens when
34843 a mailing list exists, but the sender is not on it. This router forcibly fails
34844 the address, giving a suitable error message.
34849 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
34851 .cindex "Variable Envelope Return Paths"
34852 .cindex "envelope sender"
34853 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
34854 are a way of helping mailing list administrators discover which subscription
34855 address is the cause of a particular delivery failure. The idea is to encode
34856 the original recipient address in the outgoing envelope sender address, so that
34857 if the message is forwarded by another host and then subsequently bounces, the
34858 original recipient can be extracted from the recipient address of the bounce.
34860 .oindex &%errors_to%&
34861 .oindex &%return_path%&
34862 Envelope sender addresses can be modified by Exim using two different
34863 facilities: the &%errors_to%& option on a router (as shown in previous mailing
34864 list examples), or the &%return_path%& option on a transport. The second of
34865 these is effective only if the message is successfully delivered to another
34866 host; it is not used for errors detected on the local host (see the description
34867 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
34868 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
34874 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34875 {$1-request+$local_part=$domain@your.dom.example}fail}
34877 This has the effect of rewriting the return path (envelope sender) on outgoing
34878 SMTP messages, if the local part of the original return path ends in
34879 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
34880 local part and domain of the recipient into the return path. Suppose, for
34881 example, that a message whose return path has been set to
34882 &'somelist-request@your.dom.example'& is sent to
34883 &'subscriber@other.dom.example'&. In the transport, the return path is
34886 somelist-request+subscriber=other.dom.example@your.dom.example
34888 .vindex "&$local_part$&"
34889 For this to work, you must tell Exim to send multiple copies of messages that
34890 have more than one recipient, so that each copy has just one recipient. This is
34891 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
34892 might be sent to several different recipients in the same domain, in which case
34893 &$local_part$& is not available in the transport, because it is not unique.
34895 Unless your host is doing nothing but mailing list deliveries, you should
34896 probably use a separate transport for the VERP deliveries, so as not to use
34897 extra resources in making one-per-recipient copies for other deliveries. This
34898 can easily be done by expanding the &%transport%& option in the router:
34902 domains = ! +local_domains
34904 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
34905 {verp_smtp}{remote_smtp}}
34908 If you want to change the return path using &%errors_to%& in a router instead
34909 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
34910 routers that handle mailing list addresses. This will ensure that all delivery
34911 errors, including those detected on the local host, are sent to the VERP
34914 On a host that does no local deliveries and has no manual routing, only the
34915 &(dnslookup)& router needs to be changed. A special transport is not needed for
34916 SMTP deliveries. Every mailing list recipient has its own return path value,
34917 and so Exim must hand them to the transport one at a time. Here is an example
34918 of a &(dnslookup)& router that implements VERP:
34922 domains = ! +local_domains
34923 transport = remote_smtp
34925 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
34926 {$1-request+$local_part=$domain@your.dom.example}fail}
34929 Before you start sending out messages with VERPed return paths, you must also
34930 configure Exim to accept the bounce messages that come back to those paths.
34931 Typically this is done by setting a &%local_part_suffix%& option for a
34932 router, and using this to route the messages to wherever you want to handle
34935 The overhead incurred in using VERP depends very much on the size of the
34936 message, the number of recipient addresses that resolve to the same remote
34937 host, and the speed of the connection over which the message is being sent. If
34938 a lot of addresses resolve to the same host and the connection is slow, sending
34939 a separate copy of the message for each address may take substantially longer
34940 than sending a single copy with many recipients (for which VERP cannot be
34948 .section "Virtual domains" "SECTvirtualdomains"
34949 .cindex "virtual domains"
34950 .cindex "domain" "virtual"
34951 The phrase &'virtual domain'& is unfortunately used with two rather different
34955 A domain for which there are no real mailboxes; all valid local parts are
34956 aliases for other email addresses. Common examples are organizational
34957 top-level domains and &"vanity"& domains.
34959 One of a number of independent domains that are all handled by the same host,
34960 with mailboxes on that host, but where the mailbox owners do not necessarily
34961 have login accounts on that host.
34964 The first usage is probably more common, and does seem more &"virtual"& than
34965 the second. This kind of domain can be handled in Exim with a straightforward
34966 aliasing router. One approach is to create a separate alias file for each
34967 virtual domain. Exim can test for the existence of the alias file to determine
34968 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
34969 to a router of this form:
34973 domains = dsearch;/etc/mail/virtual
34974 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
34977 The &%domains%& option specifies that the router is to be skipped, unless there
34978 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
34979 domain that is being processed. When the router runs, it looks up the local
34980 part in the file to find a new address (or list of addresses). The &%no_more%&
34981 setting ensures that if the lookup fails (leading to &%data%& being an empty
34982 string), Exim gives up on the address without trying any subsequent routers.
34984 This one router can handle all the virtual domains because the alias file names
34985 follow a fixed pattern. Permissions can be arranged so that appropriate people
34986 can edit the different alias files. A successful aliasing operation results in
34987 a new envelope recipient address, which is then routed from scratch.
34989 The other kind of &"virtual"& domain can also be handled in a straightforward
34990 way. One approach is to create a file for each domain containing a list of
34991 valid local parts, and use it in a router like this:
34995 domains = dsearch;/etc/mail/domains
34996 local_parts = lsearch;/etc/mail/domains/$domain
34997 transport = my_mailboxes
34999 The address is accepted if there is a file for the domain, and the local part
35000 can be found in the file. The &%domains%& option is used to check for the
35001 file's existence because &%domains%& is tested before the &%local_parts%&
35002 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
35003 because that option is tested after &%local_parts%&. The transport is as
35007 driver = appendfile
35008 file = /var/mail/$domain/$local_part
35011 This uses a directory of mailboxes for each domain. The &%user%& setting is
35012 required, to specify which uid is to be used for writing to the mailboxes.
35014 The configuration shown here is just one example of how you might support this
35015 requirement. There are many other ways this kind of configuration can be set
35016 up, for example, by using a database instead of separate files to hold all the
35017 information about the domains.
35021 .section "Multiple user mailboxes" "SECTmulbox"
35022 .cindex "multiple mailboxes"
35023 .cindex "mailbox" "multiple"
35024 .cindex "local part" "prefix"
35025 .cindex "local part" "suffix"
35026 Heavy email users often want to operate with multiple mailboxes, into which
35027 incoming mail is automatically sorted. A popular way of handling this is to
35028 allow users to use multiple sender addresses, so that replies can easily be
35029 identified. Users are permitted to add prefixes or suffixes to their local
35030 parts for this purpose. The wildcard facility of the generic router options
35031 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
35032 example, consider this router:
35037 file = $home/.forward
35038 local_part_suffix = -*
35039 local_part_suffix_optional
35042 .vindex "&$local_part_suffix$&"
35043 It runs a user's &_.forward_& file for all local parts of the form
35044 &'username-*'&. Within the filter file the user can distinguish different
35045 cases by testing the variable &$local_part_suffix$&. For example:
35047 if $local_part_suffix contains -special then
35048 save /home/$local_part/Mail/special
35051 If the filter file does not exist, or does not deal with such addresses, they
35052 fall through to subsequent routers, and, assuming no subsequent use of the
35053 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
35054 control over which suffixes are valid.
35056 Alternatively, a suffix can be used to trigger the use of a different
35057 &_.forward_& file &-- which is the way a similar facility is implemented in
35063 file = $home/.forward$local_part_suffix
35064 local_part_suffix = -*
35065 local_part_suffix_optional
35068 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
35069 example, &_.forward-special_& is used. Once again, if the appropriate file
35070 does not exist, or does not deal with the address, it is passed on to
35071 subsequent routers, which could, if required, look for an unqualified
35072 &_.forward_& file to use as a default.
35076 .section "Simplified vacation processing" "SECID244"
35077 .cindex "vacation processing"
35078 The traditional way of running the &'vacation'& program is for a user to set up
35079 a pipe command in a &_.forward_& file
35080 (see section &<<SECTspecitredli>>& for syntax details).
35081 This is prone to error by inexperienced users. There are two features of Exim
35082 that can be used to make this process simpler for users:
35085 A local part prefix such as &"vacation-"& can be specified on a router which
35086 can cause the message to be delivered directly to the &'vacation'& program, or
35087 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
35088 &_.forward_& file are then much simpler. For example:
35090 spqr, vacation-spqr
35093 The &%require_files%& generic router option can be used to trigger a
35094 vacation delivery by checking for the existence of a certain file in the
35095 user's home directory. The &%unseen%& generic option should also be used, to
35096 ensure that the original delivery also proceeds. In this case, all the user has
35097 to do is to create a file called, say, &_.vacation_&, containing a vacation
35101 Another advantage of both these methods is that they both work even when the
35102 use of arbitrary pipes by users is locked out.
35106 .section "Taking copies of mail" "SECID245"
35107 .cindex "message" "copying every"
35108 Some installations have policies that require archive copies of all messages to
35109 be made. A single copy of each message can easily be taken by an appropriate
35110 command in a system filter, which could, for example, use a different file for
35111 each day's messages.
35113 There is also a shadow transport mechanism that can be used to take copies of
35114 messages that are successfully delivered by local transports, one copy per
35115 delivery. This could be used, &'inter alia'&, to implement automatic
35116 notification of delivery by sites that insist on doing such things.
35120 .section "Intermittently connected hosts" "SECID246"
35121 .cindex "intermittently connected hosts"
35122 It has become quite common (because it is cheaper) for hosts to connect to the
35123 Internet periodically rather than remain connected all the time. The normal
35124 arrangement is that mail for such hosts accumulates on a system that is
35125 permanently connected.
35127 Exim was designed for use on permanently connected hosts, and so it is not
35128 particularly well-suited to use in an intermittently connected environment.
35129 Nevertheless there are some features that can be used.
35132 .section "Exim on the upstream server host" "SECID247"
35133 It is tempting to arrange for incoming mail for the intermittently connected
35134 host to remain on Exim's queue until the client connects. However, this
35135 approach does not scale very well. Two different kinds of waiting message are
35136 being mixed up in the same queue &-- those that cannot be delivered because of
35137 some temporary problem, and those that are waiting for their destination host
35138 to connect. This makes it hard to manage the queue, as well as wasting
35139 resources, because each queue runner scans the entire queue.
35141 A better approach is to separate off those messages that are waiting for an
35142 intermittently connected host. This can be done by delivering these messages
35143 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
35144 format, from where they are transmitted by other software when their
35145 destination connects. This makes it easy to collect all the mail for one host
35146 in a single directory, and to apply local timeout rules on a per-message basis
35149 On a very small scale, leaving the mail on Exim's queue can be made to work. If
35150 you are doing this, you should configure Exim with a long retry period for the
35151 intermittent host. For example:
35153 cheshire.wonderland.fict.example * F,5d,24h
35155 This stops a lot of failed delivery attempts from occurring, but Exim remembers
35156 which messages it has queued up for that host. Once the intermittent host comes
35157 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
35158 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
35159 causes all the queued up messages to be delivered, often down a single SMTP
35160 connection. While the host remains connected, any new messages get delivered
35163 If the connecting hosts do not have fixed IP addresses, that is, if a host is
35164 issued with a different IP address each time it connects, Exim's retry
35165 mechanisms on the holding host get confused, because the IP address is normally
35166 used as part of the key string for holding retry information. This can be
35167 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
35168 Since this has disadvantages for permanently connected hosts, it is best to
35169 arrange a separate transport for the intermittently connected ones.
35173 .section "Exim on the intermittently connected client host" "SECID248"
35174 The value of &%smtp_accept_queue_per_connection%& should probably be
35175 increased, or even set to zero (that is, disabled) on the intermittently
35176 connected host, so that all incoming messages down a single connection get
35177 delivered immediately.
35179 .cindex "SMTP" "passed connection"
35180 .cindex "SMTP" "multiple deliveries"
35181 .cindex "multiple SMTP deliveries"
35182 Mail waiting to be sent from an intermittently connected host will probably
35183 not have been routed, because without a connection DNS lookups are not
35184 possible. This means that if a normal queue run is done at connection time,
35185 each message is likely to be sent in a separate SMTP session. This can be
35186 avoided by starting the queue run with a command line option beginning with
35187 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
35188 first pass, routing is done but no deliveries take place. The second pass is a
35189 normal queue run; since all the messages have been previously routed, those
35190 destined for the same host are likely to get sent as multiple deliveries in a
35191 single SMTP connection.
35195 . ////////////////////////////////////////////////////////////////////////////
35196 . ////////////////////////////////////////////////////////////////////////////
35198 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
35199 "Exim as a non-queueing client"
35200 .cindex "client, non-queueing"
35201 .cindex "smart host" "suppressing queueing"
35202 On a personal computer, it is a common requirement for all
35203 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
35204 configured to operate that way, for all the popular operating systems.
35205 However, there are some MUAs for Unix-like systems that cannot be so
35206 configured: they submit messages using the command line interface of
35207 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
35210 If the personal computer runs continuously, there is no problem, because it can
35211 run a conventional MTA that handles delivery to the smart host, and deal with
35212 any delays via its queueing mechanism. However, if the computer does not run
35213 continuously or runs different operating systems at different times, queueing
35214 email is not desirable.
35216 There is therefore a requirement for something that can provide the
35217 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
35218 any queueing or retrying facilities. Furthermore, the delivery to the smart
35219 host should be synchronous, so that if it fails, the sending MUA is immediately
35220 informed. In other words, we want something that extends an MUA that submits
35221 to a local MTA via the command line so that it behaves like one that submits
35222 to a remote smart host using TCP/SMTP.
35224 There are a number of applications (for example, there is one called &'ssmtp'&)
35225 that do this job. However, people have found them to be lacking in various
35226 ways. For instance, you might want to allow aliasing and forwarding to be done
35227 before sending a message to the smart host.
35229 Exim already had the necessary infrastructure for doing this job. Just a few
35230 tweaks were needed to make it behave as required, though it is somewhat of an
35231 overkill to use a fully-featured MTA for this purpose.
35233 .oindex "&%mua_wrapper%&"
35234 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
35235 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
35236 assumes that it is being used to &"wrap"& a command-line MUA in the manner
35237 just described. As well as setting &%mua_wrapper%&, you also need to provide a
35238 compatible router and transport configuration. Typically there will be just one
35239 router and one transport, sending everything to a smart host.
35241 When run in MUA wrapping mode, the behaviour of Exim changes in the
35245 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
35246 In other words, the only way to submit messages is via the command line.
35248 Each message is synchronously delivered as soon as it is received (&%-odi%& is
35249 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
35250 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
35251 does not finish until the delivery attempt is complete. If the delivery is
35252 successful, a zero return code is given.
35254 Address redirection is permitted, but the final routing for all addresses must
35255 be to the same remote transport, and to the same list of hosts. Furthermore,
35256 the return address (envelope sender) must be the same for all recipients, as
35257 must any added or deleted header lines. In other words, it must be possible to
35258 deliver the message in a single SMTP transaction, however many recipients there
35261 If these conditions are not met, or if routing any address results in a
35262 failure or defer status, or if Exim is unable to deliver all the recipients
35263 successfully to one of the smart hosts, delivery of the entire message fails.
35265 Because no queueing is allowed, all failures are treated as permanent; there
35266 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
35267 smart host. Furthermore, because only a single yes/no response can be given to
35268 the caller, it is not possible to deliver to some recipients and not others. If
35269 there is an error (temporary or permanent) for any recipient, all are failed.
35271 If more than one smart host is listed, Exim will try another host after a
35272 connection failure or a timeout, in the normal way. However, if this kind of
35273 failure happens for all the hosts, the delivery fails.
35275 When delivery fails, an error message is written to the standard error stream
35276 (as well as to Exim's log), and Exim exits to the caller with a return code
35277 value 1. The message is expunged from Exim's spool files. No bounce messages
35278 are ever generated.
35280 No retry data is maintained, and any retry rules are ignored.
35282 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
35283 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
35284 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
35287 The overall effect is that Exim makes a single synchronous attempt to deliver
35288 the message, failing if there is any kind of problem. Because no local
35289 deliveries are done and no daemon can be run, Exim does not need root
35290 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
35291 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
35292 the advantages and disadvantages of running without root privilege.
35297 . ////////////////////////////////////////////////////////////////////////////
35298 . ////////////////////////////////////////////////////////////////////////////
35300 .chapter "Log files" "CHAPlog"
35301 .scindex IIDloggen "log" "general description"
35302 .cindex "log" "types of"
35303 Exim writes three different logs, referred to as the main log, the reject log,
35308 The main log records the arrival of each message and each delivery in a single
35309 line in each case. The format is as compact as possible, in an attempt to keep
35310 down the size of log files. Two-character flag sequences make it easy to pick
35311 out these lines. A number of other events are recorded in the main log. Some of
35312 them are optional, in which case the &%log_selector%& option controls whether
35313 they are included or not. A Perl script called &'eximstats'&, which does simple
35314 analysis of main log files, is provided in the Exim distribution (see section
35315 &<<SECTmailstat>>&).
35317 .cindex "reject log"
35318 The reject log records information from messages that are rejected as a result
35319 of a configuration option (that is, for policy reasons).
35320 The first line of each rejection is a copy of the line that is also written to
35321 the main log. Then, if the message's header has been read at the time the log
35322 is written, its contents are written to this log. Only the original header
35323 lines are available; header lines added by ACLs are not logged. You can use the
35324 reject log to check that your policy controls are working correctly; on a busy
35325 host this may be easier than scanning the main log for rejection messages. You
35326 can suppress the writing of the reject log by setting &%write_rejectlog%&
35329 .cindex "panic log"
35330 .cindex "system log"
35331 When certain serious errors occur, Exim writes entries to its panic log. If the
35332 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
35333 are usually written to the main log as well, but can get lost amid the mass of
35334 other entries. The panic log should be empty under normal circumstances. It is
35335 therefore a good idea to check it (or to have a &'cron'& script check it)
35336 regularly, in order to become aware of any problems. When Exim cannot open its
35337 panic log, it tries as a last resort to write to the system log (syslog). This
35338 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
35339 message itself is written at priority LOG_CRIT.
35342 Every log line starts with a timestamp, in the format shown in the following
35343 example. Note that many of the examples shown in this chapter are line-wrapped.
35344 In the log file, this would be all on one line:
35346 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
35349 By default, the timestamps are in the local timezone. There are two
35350 ways of changing this:
35353 You can set the &%timezone%& option to a different time zone; in particular, if
35358 the timestamps will be in UTC (aka GMT).
35360 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
35363 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
35367 .cindex "log" "process ids in"
35368 .cindex "pid (process id)" "in log lines"
35369 Exim does not include its process id in log lines by default, but you can
35370 request that it does so by specifying the &`pid`& log selector (see section
35371 &<<SECTlogselector>>&). When this is set, the process id is output, in square
35372 brackets, immediately after the time and date.
35377 .section "Where the logs are written" "SECTwhelogwri"
35378 .cindex "log" "destination"
35379 .cindex "log" "to file"
35380 .cindex "log" "to syslog"
35382 The logs may be written to local files, or to syslog, or both. However, it
35383 should be noted that many syslog implementations use UDP as a transport, and
35384 are therefore unreliable in the sense that messages are not guaranteed to
35385 arrive at the loghost, nor is the ordering of messages necessarily maintained.
35386 It has also been reported that on large log files (tens of megabytes) you may
35387 need to tweak syslog to prevent it syncing the file with each write &-- on
35388 Linux this has been seen to make syslog take 90% plus of CPU time.
35390 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
35391 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
35392 configuration. This latter string is expanded, so it can contain, for example,
35393 references to the host name:
35395 log_file_path = /var/log/$primary_hostname/exim_%slog
35397 It is generally advisable, however, to set the string in &_Local/Makefile_&
35398 rather than at run time, because then the setting is available right from the
35399 start of Exim's execution. Otherwise, if there's something it wants to log
35400 before it has read the configuration file (for example, an error in the
35401 configuration file) it will not use the path you want, and may not be able to
35404 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
35405 list, currently limited to at most two items. This is one option where the
35406 facility for changing a list separator may not be used. The list must always be
35407 colon-separated. If an item in the list is &"syslog"& then syslog is used;
35408 otherwise the item must either be an absolute path, containing &`%s`& at the
35409 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
35410 implying the use of a default path.
35412 When Exim encounters an empty item in the list, it searches the list defined by
35413 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
35414 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
35415 mean &"use the path specified at build time"&. It no such item exists, log
35416 files are written in the &_log_& subdirectory of the spool directory. This is
35417 equivalent to the setting:
35419 log_file_path = $spool_directory/log/%slog
35421 If you do not specify anything at build time or run time,
35422 or if you unset the option at run time (i.e. &`log_file_path = `&),
35423 that is where the logs are written.
35425 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
35426 are in use &-- see section &<<SECTdatlogfil>>& below.
35428 Here are some examples of possible settings:
35430 &`LOG_FILE_PATH=syslog `& syslog only
35431 &`LOG_FILE_PATH=:syslog `& syslog and default path
35432 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
35433 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
35435 If there are more than two paths in the list, the first is used and a panic
35440 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
35441 .cindex "log" "cycling local files"
35442 .cindex "cycling logs"
35443 .cindex "&'exicyclog'&"
35444 .cindex "log" "local files; writing to"
35445 Some operating systems provide centralized and standardized methods for cycling
35446 log files. For those that do not, a utility script called &'exicyclog'& is
35447 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
35448 main and reject logs each time it is called. The maximum number of old logs to
35449 keep can be set. It is suggested this script is run as a daily &'cron'& job.
35451 An Exim delivery process opens the main log when it first needs to write to it,
35452 and it keeps the file open in case subsequent entries are required &-- for
35453 example, if a number of different deliveries are being done for the same
35454 message. However, remote SMTP deliveries can take a long time, and this means
35455 that the file may be kept open long after it is renamed if &'exicyclog'& or
35456 something similar is being used to rename log files on a regular basis. To
35457 ensure that a switch of log files is noticed as soon as possible, Exim calls
35458 &[stat()]& on the main log's name before reusing an open file, and if the file
35459 does not exist, or its inode has changed, the old file is closed and Exim
35460 tries to open the main log from scratch. Thus, an old log file may remain open
35461 for quite some time, but no Exim processes should write to it once it has been
35466 .section "Datestamped log files" "SECTdatlogfil"
35467 .cindex "log" "datestamped files"
35468 Instead of cycling the main and reject log files by renaming them
35469 periodically, some sites like to use files whose names contain a datestamp,
35470 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
35471 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
35472 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
35473 point where the datestamp is required. For example:
35475 log_file_path = /var/spool/exim/log/%slog-%D
35476 log_file_path = /var/log/exim-%s-%D.log
35477 log_file_path = /var/spool/exim/log/%D-%slog
35478 log_file_path = /var/log/exim/%s.%M
35480 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
35481 examples of names generated by the above examples:
35483 /var/spool/exim/log/mainlog-20021225
35484 /var/log/exim-reject-20021225.log
35485 /var/spool/exim/log/20021225-mainlog
35486 /var/log/exim/main.200212
35488 When this form of log file is specified, Exim automatically switches to new
35489 files at midnight. It does not make any attempt to compress old logs; you
35490 will need to write your own script if you require this. You should not
35491 run &'exicyclog'& with this form of logging.
35493 The location of the panic log is also determined by &%log_file_path%&, but it
35494 is not datestamped, because rotation of the panic log does not make sense.
35495 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
35496 the string. In addition, if it immediately follows a slash, a following
35497 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
35498 character is removed. Thus, the four examples above would give these panic
35501 /var/spool/exim/log/paniclog
35502 /var/log/exim-panic.log
35503 /var/spool/exim/log/paniclog
35504 /var/log/exim/panic
35508 .section "Logging to syslog" "SECID249"
35509 .cindex "log" "syslog; writing to"
35510 The use of syslog does not change what Exim logs or the format of its messages,
35511 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
35512 Exim's log lines are omitted when these lines are sent to syslog. Apart from
35513 that, the same strings are written to syslog as to log files. The syslog
35514 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
35515 by default, but you can change these by setting the &%syslog_facility%& and
35516 &%syslog_processname%& options, respectively. If Exim was compiled with
35517 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
35518 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
35519 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
35520 the time and host name to each line.
35521 The three log streams are mapped onto syslog priorities as follows:
35524 &'mainlog'& is mapped to LOG_INFO
35526 &'rejectlog'& is mapped to LOG_NOTICE
35528 &'paniclog'& is mapped to LOG_ALERT
35531 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
35532 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
35533 these are routed by syslog to the same place. You can suppress this duplication
35534 by setting &%syslog_duplication%& false.
35536 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
35537 entries contain multiple lines when headers are included. To cope with both
35538 these cases, entries written to syslog are split into separate &[syslog()]&
35539 calls at each internal newline, and also after a maximum of
35540 870 data characters. (This allows for a total syslog line length of 1024, when
35541 additions such as timestamps are added.) If you are running a syslog
35542 replacement that can handle lines longer than the 1024 characters allowed by
35543 RFC 3164, you should set
35545 SYSLOG_LONG_LINES=yes
35547 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
35548 lines, but it still splits at internal newlines in &'reject'& log entries.
35550 To make it easy to re-assemble split lines later, each component of a split
35551 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
35552 where <&'n'&> is the component number and <&'m'&> is the total number of
35553 components in the entry. The / delimiter is used when the line was split
35554 because it was too long; if it was split because of an internal newline, the \
35555 delimiter is used. For example, supposing the length limit to be 50 instead of
35556 870, the following would be the result of a typical rejection message to
35557 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
35558 name, and pid as added by syslog:
35560 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
35561 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
35562 [3/5] when scanning for sender: missing or malformed lo
35563 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
35566 The same error might cause the following lines to be written to &"rejectlog"&
35569 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
35570 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
35571 [3/18] er when scanning for sender: missing or malformed
35572 [4/18] local part in "<>" (envelope sender is <ph10@cam
35574 [6\18] Recipients: ph10@some.domain.cam.example
35575 [7\18] P Received: from [127.0.0.1] (ident=ph10)
35576 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
35577 [9\18] id 16RdAL-0006pc-00
35578 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
35579 [11\18] 09:43 +0100
35581 [13\18] Subject: this is a test header
35582 [18\18] X-something: this is another header
35583 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
35586 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
35588 Log lines that are neither too long nor contain newlines are written to syslog
35589 without modification.
35591 If only syslog is being used, the Exim monitor is unable to provide a log tail
35592 display, unless syslog is routing &'mainlog'& to a file on the local host and
35593 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
35598 .section "Log line flags" "SECID250"
35599 One line is written to the main log for each message received, and for each
35600 successful, unsuccessful, and delayed delivery. These lines can readily be
35601 picked out by the distinctive two-character flags that immediately follow the
35602 timestamp. The flags are:
35604 &`<=`& message arrival
35605 &`(=`& message fakereject
35606 &`=>`& normal message delivery
35607 &`->`& additional address in same delivery
35608 &`>>`& cutthrough message delivery
35609 &`*>`& delivery suppressed by &%-N%&
35610 &`**`& delivery failed; address bounced
35611 &`==`& delivery deferred; temporary problem
35615 .section "Logging message reception" "SECID251"
35616 .cindex "log" "reception line"
35617 The format of the single-line entry in the main log that is written for every
35618 message received is shown in the basic example below, which is split over
35619 several lines in order to fit it on the page:
35621 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
35622 H=mailer.fict.example [192.168.123.123] U=exim
35623 P=smtp S=5678 id=<incoming message id>
35625 The address immediately following &"<="& is the envelope sender address. A
35626 bounce message is shown with the sender address &"<>"&, and if it is locally
35627 generated, this is followed by an item of the form
35631 which is a reference to the message that caused the bounce to be sent.
35635 For messages from other hosts, the H and U fields identify the remote host and
35636 record the RFC 1413 identity of the user that sent the message, if one was
35637 received. The number given in square brackets is the IP address of the sending
35638 host. If there is a single, unparenthesized host name in the H field, as
35639 above, it has been verified to correspond to the IP address (see the
35640 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
35641 by the remote host in the SMTP HELO or EHLO command, and has not been
35642 verified. If verification yields a different name to that given for HELO or
35643 EHLO, the verified name appears first, followed by the HELO or EHLO
35644 name in parentheses.
35646 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
35647 without brackets, in the HELO or EHLO command, leading to entries in
35648 the log containing text like these examples:
35650 H=(10.21.32.43) [192.168.8.34]
35651 H=([10.21.32.43]) [192.168.8.34]
35653 This can be confusing. Only the final address in square brackets can be relied
35656 For locally generated messages (that is, messages not received over TCP/IP),
35657 the H field is omitted, and the U field contains the login name of the caller
35660 .cindex "authentication" "logging"
35661 .cindex "AUTH" "logging"
35662 For all messages, the P field specifies the protocol used to receive the
35663 message. This is the value that is stored in &$received_protocol$&. In the case
35664 of incoming SMTP messages, the value indicates whether or not any SMTP
35665 extensions (ESMTP), encryption, or authentication were used. If the SMTP
35666 session was encrypted, there is an additional X field that records the cipher
35667 suite that was used.
35669 .cindex log protocol
35670 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
35671 hosts that have authenticated themselves using the SMTP AUTH command. The first
35672 value is used when the SMTP connection was encrypted (&"secure"&). In this case
35673 there is an additional item A= followed by the name of the authenticator that
35674 was used. If an authenticated identification was set up by the authenticator's
35675 &%server_set_id%& option, this is logged too, separated by a colon from the
35676 authenticator name.
35678 .cindex "size" "of message"
35679 The id field records the existing message id, if present. The size of the
35680 received message is given by the S field. When the message is delivered,
35681 headers may be removed or added, so that the size of delivered copies of the
35682 message may not correspond with this value (and indeed may be different to each
35685 The &%log_selector%& option can be used to request the logging of additional
35686 data when a message is received. See section &<<SECTlogselector>>& below.
35690 .section "Logging deliveries" "SECID252"
35691 .cindex "log" "delivery line"
35692 The format of the single-line entry in the main log that is written for every
35693 delivery is shown in one of the examples below, for local and remote
35694 deliveries, respectively. Each example has been split into multiple lines in order
35695 to fit it on the page:
35697 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
35698 <marv@hitch.fict.example> R=localuser T=local_delivery
35699 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
35700 monk@holistic.fict.example R=dnslookup T=remote_smtp
35701 H=holistic.fict.example [192.168.234.234]
35703 For ordinary local deliveries, the original address is given in angle brackets
35704 after the final delivery address, which might be a pipe or a file. If
35705 intermediate address(es) exist between the original and the final address, the
35706 last of these is given in parentheses after the final address. The R and T
35707 fields record the router and transport that were used to process the address.
35709 If SMTP AUTH was used for the delivery there is an additional item A=
35710 followed by the name of the authenticator that was used.
35711 If an authenticated identification was set up by the authenticator's &%client_set_id%&
35712 option, this is logged too, separated by a colon from the authenticator name.
35714 If a shadow transport was run after a successful local delivery, the log line
35715 for the successful delivery has an item added on the end, of the form
35717 &`ST=<`&&'shadow transport name'&&`>`&
35719 If the shadow transport did not succeed, the error message is put in
35720 parentheses afterwards.
35722 .cindex "asterisk" "after IP address"
35723 When more than one address is included in a single delivery (for example, two
35724 SMTP RCPT commands in one transaction) the second and subsequent addresses are
35725 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
35726 down a single SMTP connection, an asterisk follows the IP address in the log
35727 lines for the second and subsequent messages.
35729 .cindex "delivery" "cutthrough; logging"
35730 .cindex "cutthrough" "logging"
35731 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
35732 line precedes the reception line, since cutthrough waits for a possible
35733 rejection from the destination in case it can reject the sourced item.
35735 The generation of a reply message by a filter file gets logged as a
35736 &"delivery"& to the addressee, preceded by &">"&.
35738 The &%log_selector%& option can be used to request the logging of additional
35739 data when a message is delivered. See section &<<SECTlogselector>>& below.
35742 .section "Discarded deliveries" "SECID253"
35743 .cindex "discarded messages"
35744 .cindex "message" "discarded"
35745 .cindex "delivery" "discarded; logging"
35746 When a message is discarded as a result of the command &"seen finish"& being
35747 obeyed in a filter file which generates no deliveries, a log entry of the form
35749 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
35750 <low.club@bridge.example> R=userforward
35752 is written, to record why no deliveries are logged. When a message is discarded
35753 because it is aliased to &":blackhole:"& the log line is like this:
35755 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
35756 <hole@nowhere.example> R=blackhole_router
35760 .section "Deferred deliveries" "SECID254"
35761 When a delivery is deferred, a line of the following form is logged:
35763 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
35764 R=dnslookup T=smtp defer (146): Connection refused
35766 In the case of remote deliveries, the error is the one that was given for the
35767 last IP address that was tried. Details of individual SMTP failures are also
35768 written to the log, so the above line would be preceded by something like
35770 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
35771 mail1.endrest.example [192.168.239.239]: Connection refused
35773 When a deferred address is skipped because its retry time has not been reached,
35774 a message is written to the log, but this can be suppressed by setting an
35775 appropriate value in &%log_selector%&.
35779 .section "Delivery failures" "SECID255"
35780 .cindex "delivery" "failure; logging"
35781 If a delivery fails because an address cannot be routed, a line of the
35782 following form is logged:
35784 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
35785 <jim@trek99.example>: unknown mail domain
35787 If a delivery fails at transport time, the router and transport are shown, and
35788 the response from the remote host is included, as in this example:
35790 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
35791 R=dnslookup T=remote_smtp: SMTP error from remote mailer
35792 after pipelined RCPT TO:<ace400@pb.example>: host
35793 pbmail3.py.example [192.168.63.111]: 553 5.3.0
35794 <ace400@pb.example>...Addressee unknown
35796 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
35797 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
35798 disabling PIPELINING. The log lines for all forms of delivery failure are
35799 flagged with &`**`&.
35803 .section "Fake deliveries" "SECID256"
35804 .cindex "delivery" "fake; logging"
35805 If a delivery does not actually take place because the &%-N%& option has been
35806 used to suppress it, a normal delivery line is written to the log, except that
35807 &"=>"& is replaced by &"*>"&.
35811 .section "Completion" "SECID257"
35814 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
35816 is written to the main log when a message is about to be removed from the spool
35817 at the end of its processing.
35822 .section "Summary of Fields in Log Lines" "SECID258"
35823 .cindex "log" "summary of fields"
35824 A summary of the field identifiers that are used in log lines is shown in
35825 the following table:
35827 &`A `& authenticator name (and optional id and sender)
35828 &`C `& SMTP confirmation on delivery
35829 &` `& command list for &"no mail in SMTP session"&
35830 &`CV `& certificate verification status
35831 &`D `& duration of &"no mail in SMTP session"&
35832 &`DN `& distinguished name from peer certificate
35833 &`DS `& DNSSEC secured lookups
35834 &`DT `& on &`=>`& lines: time taken for a delivery
35835 &`F `& sender address (on delivery lines)
35836 &`H `& host name and IP address
35837 &`I `& local interface used
35838 &`K `& CHUNKING extension used
35839 &`id `& message id for incoming message
35840 &`P `& on &`<=`& lines: protocol used
35841 &` `& on &`=>`& and &`**`& lines: return path
35842 &`PRDR`& PRDR extension used
35843 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
35844 &`Q `& alternate queue name
35845 &`QT `& on &`=>`& lines: time spent on queue so far
35846 &` `& on &"Completed"& lines: time spent on queue
35847 &`R `& on &`<=`& lines: reference for local bounce
35848 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
35849 &`S `& size of message in bytes
35850 &`SNI `& server name indication from TLS client hello
35851 &`ST `& shadow transport name
35852 &`T `& on &`<=`& lines: message subject (topic)
35853 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
35854 &`U `& local user or RFC 1413 identity
35855 &`X `& TLS cipher suite
35859 .section "Other log entries" "SECID259"
35860 Various other types of log entry are written from time to time. Most should be
35861 self-explanatory. Among the more common are:
35864 .cindex "retry" "time not reached"
35865 &'retry time not reached'&&~&~An address previously suffered a temporary error
35866 during routing or local delivery, and the time to retry has not yet arrived.
35867 This message is not written to an individual message log file unless it happens
35868 during the first delivery attempt.
35870 &'retry time not reached for any host'&&~&~An address previously suffered
35871 temporary errors during remote delivery, and the retry time has not yet arrived
35872 for any of the hosts to which it is routed.
35874 .cindex "spool directory" "file locked"
35875 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
35876 some other Exim process is already working on the message. This can be quite
35877 common if queue running processes are started at frequent intervals. The
35878 &'exiwhat'& utility script can be used to find out what Exim processes are
35881 .cindex "error" "ignored"
35882 &'error ignored'&&~&~There are several circumstances that give rise to this
35885 Exim failed to deliver a bounce message whose age was greater than
35886 &%ignore_bounce_errors_after%&. The bounce was discarded.
35888 A filter file set up a delivery using the &"noerror"& option, and the delivery
35889 failed. The delivery was discarded.
35891 A delivery set up by a router configured with
35892 . ==== As this is a nested list, any displays it contains must be indented
35893 . ==== as otherwise they are too far to the left.
35897 failed. The delivery was discarded.
35905 .section "Reducing or increasing what is logged" "SECTlogselector"
35906 .cindex "log" "selectors"
35907 By setting the &%log_selector%& global option, you can disable some of Exim's
35908 default logging, or you can request additional logging. The value of
35909 &%log_selector%& is made up of names preceded by plus or minus characters. For
35912 log_selector = +arguments -retry_defer
35914 The list of optional log items is in the following table, with the default
35915 selection marked by asterisks:
35917 &` 8bitmime `& received 8BITMIME status
35918 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
35919 &` address_rewrite `& address rewriting
35920 &` all_parents `& all parents in => lines
35921 &` arguments `& command line arguments
35922 &`*connection_reject `& connection rejections
35923 &`*delay_delivery `& immediate delivery delayed
35924 &` deliver_time `& time taken to perform delivery
35925 &` delivery_size `& add &`S=`&&'nnn'& to => lines
35926 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
35927 &` dnssec `& DNSSEC secured lookups
35928 &`*etrn `& ETRN commands
35929 &`*host_lookup_failed `& as it says
35930 &` ident_timeout `& timeout for ident connection
35931 &` incoming_interface `& local interface on <= and => lines
35932 &` incoming_port `& remote port on <= lines
35933 &`*lost_incoming_connection `& as it says (includes timeouts)
35934 &` outgoing_interface `& local interface on => lines
35935 &` outgoing_port `& add remote port to => lines
35936 &`*queue_run `& start and end queue runs
35937 &` queue_time `& time on queue for one recipient
35938 &` queue_time_overall `& time on queue for whole message
35939 &` pid `& Exim process id
35940 &` proxy `& proxy address on <= and => lines
35941 &` received_recipients `& recipients on <= lines
35942 &` received_sender `& sender on <= lines
35943 &`*rejected_header `& header contents on reject log
35944 &`*retry_defer `& &"retry time not reached"&
35945 &` return_path_on_delivery `& put return path on => and ** lines
35946 &` sender_on_delivery `& add sender to => lines
35947 &`*sender_verify_fail `& sender verification failures
35948 &`*size_reject `& rejection because too big
35949 &`*skip_delivery `& delivery skipped in a queue run
35950 &`*smtp_confirmation `& SMTP confirmation on => lines
35951 &` smtp_connection `& incoming SMTP connections
35952 &` smtp_incomplete_transaction`& incomplete SMTP transactions
35953 &` smtp_mailauth `& AUTH argument to MAIL commands
35954 &` smtp_no_mail `& session with no MAIL commands
35955 &` smtp_protocol_error `& SMTP protocol errors
35956 &` smtp_syntax_error `& SMTP syntax errors
35957 &` subject `& contents of &'Subject:'& on <= lines
35958 &`*tls_certificate_verified `& certificate verification status
35959 &`*tls_cipher `& TLS cipher suite on <= and => lines
35960 &` tls_peerdn `& TLS peer DN on <= and => lines
35961 &` tls_sni `& TLS SNI on <= lines
35962 &` unknown_in_list `& DNS lookup failed in list match
35964 &` all `& all of the above
35966 See also the &%slow_lookup_log%& main configuration option,
35967 section &<<SECID99>>&
35969 More details on each of these items follows:
35973 .cindex "log" "8BITMIME"
35974 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
35975 which may help in tracking down interoperability issues with ancient MTAs
35976 that are not 8bit clean. This is added to the &"<="& line, tagged with
35977 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
35978 &`7BIT`& and &`8BITMIME`& respectively.
35980 .cindex "&%warn%& ACL verb" "log when skipping"
35981 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
35982 its conditions cannot be evaluated, a log line to this effect is written if
35983 this log selector is set.
35985 .cindex "log" "rewriting"
35986 .cindex "rewriting" "logging"
35987 &%address_rewrite%&: This applies both to global rewrites and per-transport
35988 rewrites, but not to rewrites in filters run as an unprivileged user (because
35989 such users cannot access the log).
35991 .cindex "log" "full parentage"
35992 &%all_parents%&: Normally only the original and final addresses are logged on
35993 delivery lines; with this selector, intermediate parents are given in
35994 parentheses between them.
35996 .cindex "log" "Exim arguments"
35997 .cindex "Exim arguments, logging"
35998 &%arguments%&: This causes Exim to write the arguments with which it was called
35999 to the main log, preceded by the current working directory. This is a debugging
36000 feature, added to make it easier to find out how certain MUAs call
36001 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
36002 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
36003 that are empty or that contain white space are quoted. Non-printing characters
36004 are shown as escape sequences. This facility cannot log unrecognized arguments,
36005 because the arguments are checked before the configuration file is read. The
36006 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
36007 between the caller and Exim.
36009 .cindex "log" "connection rejections"
36010 &%connection_reject%&: A log entry is written whenever an incoming SMTP
36011 connection is rejected, for whatever reason.
36013 .cindex "log" "delayed delivery"
36014 .cindex "delayed delivery, logging"
36015 &%delay_delivery%&: A log entry is written whenever a delivery process is not
36016 started for an incoming message because the load is too high or too many
36017 messages were received on one connection. Logging does not occur if no delivery
36018 process is started because &%queue_only%& is set or &%-odq%& was used.
36020 .cindex "log" "delivery duration"
36021 &%deliver_time%&: For each delivery, the amount of real time it has taken to
36022 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
36024 .cindex "log" "message size on delivery"
36025 .cindex "size" "of message"
36026 &%delivery_size%&: For each delivery, the size of message delivered is added to
36027 the &"=>"& line, tagged with S=.
36029 .cindex "log" "dnslist defer"
36030 .cindex "DNS list" "logging defer"
36031 .cindex "black list (DNS)"
36032 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
36033 DNS black list suffers a temporary error.
36036 .cindex dnssec logging
36037 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
36038 dns lookups gave secure results a tag of DS is added.
36039 For acceptance this covers the reverse and forward lookups for host name verification.
36040 It does not cover helo-name verification.
36041 For delivery this covers the SRV, MX, A and/or AAAA lookups.
36043 .cindex "log" "ETRN commands"
36044 .cindex "ETRN" "logging"
36045 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
36046 is run to determine whether or not it is actually accepted. An invalid ETRN
36047 command, or one received within a message transaction is not logged by this
36048 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
36050 .cindex "log" "host lookup failure"
36051 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
36052 any addresses, or when a lookup of an IP address fails to find a host name, a
36053 log line is written. This logging does not apply to direct DNS lookups when
36054 routing email addresses, but it does apply to &"byname"& lookups.
36056 .cindex "log" "ident timeout"
36057 .cindex "RFC 1413" "logging timeout"
36058 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
36059 client's ident port times out.
36061 .cindex "log" "incoming interface"
36062 .cindex "log" "local interface"
36063 .cindex "log" "local address and port"
36064 .cindex "TCP/IP" "logging local address and port"
36065 .cindex "interface" "logging"
36066 &%incoming_interface%&: The interface on which a message was received is added
36067 to the &"<="& line as an IP address in square brackets, tagged by I= and
36068 followed by a colon and the port number. The local interface and port are also
36069 added to other SMTP log lines, for example &"SMTP connection from"&, to
36070 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
36071 The latter can be disabled by turning off the &%outgoing_interface%& option.
36073 .cindex log "incoming proxy address"
36074 .cindex proxy "logging proxy address"
36075 .cindex "TCP/IP" "logging proxy address"
36076 &%proxy%&: The internal (closest to the system running Exim) IP address
36077 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
36078 on a proxied connection
36079 or the &"=>"& line for a message delivered on a proxied connection.
36080 See &<<SECTproxyInbound>>& for more information.
36082 .cindex "log" "incoming remote port"
36083 .cindex "port" "logging remote"
36084 .cindex "TCP/IP" "logging incoming remote port"
36085 .vindex "&$sender_fullhost$&"
36086 .vindex "&$sender_rcvhost$&"
36087 &%incoming_port%&: The remote port number from which a message was received is
36088 added to log entries and &'Received:'& header lines, following the IP address
36089 in square brackets, and separated from it by a colon. This is implemented by
36090 changing the value that is put in the &$sender_fullhost$& and
36091 &$sender_rcvhost$& variables. Recording the remote port number has become more
36092 important with the widening use of NAT (see RFC 2505).
36094 .cindex "log" "dropped connection"
36095 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
36096 connection is unexpectedly dropped.
36098 .cindex "log" "outgoing interface"
36099 .cindex "log" "local interface"
36100 .cindex "log" "local address and port"
36101 .cindex "TCP/IP" "logging local address and port"
36102 .cindex "interface" "logging"
36103 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
36104 interface on which a message was sent is added to delivery lines as an I= tag
36105 followed by IP address in square brackets. You can disable this by turning
36106 off the &%outgoing_interface%& option.
36108 .cindex "log" "outgoing remote port"
36109 .cindex "port" "logging outgoint remote"
36110 .cindex "TCP/IP" "logging outgoing remote port"
36111 &%outgoing_port%&: The remote port number is added to delivery log lines (those
36112 containing => tags) following the IP address.
36113 The local port is also added if &%incoming_interface%& and
36114 &%outgoing_interface%& are both enabled.
36115 This option is not included in the default setting, because for most ordinary
36116 configurations, the remote port number is always 25 (the SMTP port), and the
36117 local port is a random ephemeral port.
36119 .cindex "log" "process ids in"
36120 .cindex "pid (process id)" "in log lines"
36121 &%pid%&: The current process id is added to every log line, in square brackets,
36122 immediately after the time and date.
36124 .cindex "log" "queue run"
36125 .cindex "queue runner" "logging"
36126 &%queue_run%&: The start and end of every queue run are logged.
36128 .cindex "log" "queue time"
36129 &%queue_time%&: The amount of time the message has been in the queue on the
36130 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
36131 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
36132 includes reception time as well as the delivery time for the current address.
36133 This means that it may be longer than the difference between the arrival and
36134 delivery log line times, because the arrival log line is not written until the
36135 message has been successfully received.
36137 &%queue_time_overall%&: The amount of time the message has been in the queue on
36138 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
36139 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
36140 message, so it includes reception time as well as the total delivery time.
36142 .cindex "log" "recipients"
36143 &%received_recipients%&: The recipients of a message are listed in the main log
36144 as soon as the message is received. The list appears at the end of the log line
36145 that is written when a message is received, preceded by the word &"for"&. The
36146 addresses are listed after they have been qualified, but before any rewriting
36148 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
36151 .cindex "log" "sender reception"
36152 &%received_sender%&: The unrewritten original sender of a message is added to
36153 the end of the log line that records the message's arrival, after the word
36154 &"from"& (before the recipients if &%received_recipients%& is also set).
36156 .cindex "log" "header lines for rejection"
36157 &%rejected_header%&: If a message's header has been received at the time a
36158 rejection is written to the reject log, the complete header is added to the
36159 log. Header logging can be turned off individually for messages that are
36160 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
36162 .cindex "log" "retry defer"
36163 &%retry_defer%&: A log line is written if a delivery is deferred because a
36164 retry time has not yet been reached. However, this &"retry time not reached"&
36165 message is always omitted from individual message logs after the first delivery
36168 .cindex "log" "return path"
36169 &%return_path_on_delivery%&: The return path that is being transmitted with
36170 the message is included in delivery and bounce lines, using the tag P=.
36171 This is omitted if no delivery actually happens, for example, if routing fails,
36172 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
36174 .cindex "log" "sender on delivery"
36175 &%sender_on_delivery%&: The message's sender address is added to every delivery
36176 and bounce line, tagged by F= (for &"from"&).
36177 This is the original sender that was received with the message; it is not
36178 necessarily the same as the outgoing return path.
36180 .cindex "log" "sender verify failure"
36181 &%sender_verify_fail%&: If this selector is unset, the separate log line that
36182 gives details of a sender verification failure is not written. Log lines for
36183 the rejection of SMTP commands contain just &"sender verify failed"&, so some
36186 .cindex "log" "size rejection"
36187 &%size_reject%&: A log line is written whenever a message is rejected because
36190 .cindex "log" "frozen messages; skipped"
36191 .cindex "frozen messages" "logging skipping"
36192 &%skip_delivery%&: A log line is written whenever a message is skipped during a
36193 queue run because it is frozen or because another process is already delivering
36195 .cindex "&""spool file is locked""&"
36196 The message that is written is &"spool file is locked"&.
36198 .cindex "log" "smtp confirmation"
36199 .cindex "SMTP" "logging confirmation"
36200 .cindex "LMTP" "logging confirmation"
36201 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
36202 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
36203 A number of MTAs (including Exim) return an identifying string in this
36206 .cindex "log" "SMTP connections"
36207 .cindex "SMTP" "logging connections"
36208 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
36209 established or closed, unless the connection is from a host that matches
36210 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
36211 only when the closure is unexpected.) This applies to connections from local
36212 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
36213 dropped in the middle of a message, a log line is always written, whether or
36214 not this selector is set, but otherwise nothing is written at the start and end
36215 of connections unless this selector is enabled.
36217 For TCP/IP connections to an Exim daemon, the current number of connections is
36218 included in the log message for each new connection, but note that the count is
36219 reset if the daemon is restarted.
36220 Also, because connections are closed (and the closure is logged) in
36221 subprocesses, the count may not include connections that have been closed but
36222 whose termination the daemon has not yet noticed. Thus, while it is possible to
36223 match up the opening and closing of connections in the log, the value of the
36224 logged counts may not be entirely accurate.
36226 .cindex "log" "SMTP transaction; incomplete"
36227 .cindex "SMTP" "logging incomplete transactions"
36228 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
36229 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
36230 and the message sender plus any accepted recipients are included in the log
36231 line. This can provide evidence of dictionary attacks.
36233 .cindex "log" "non-MAIL SMTP sessions"
36234 .cindex "MAIL" "logging session without"
36235 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
36236 connection terminates without having issued a MAIL command. This includes both
36237 the case when the connection is dropped, and the case when QUIT is used. It
36238 does not include cases where the connection is rejected right at the start (by
36239 an ACL, or because there are too many connections, or whatever). These cases
36240 already have their own log lines.
36242 The log line that is written contains the identity of the client in the usual
36243 way, followed by D= and a time, which records the duration of the connection.
36244 If the connection was authenticated, this fact is logged exactly as it is for
36245 an incoming message, with an A= item. If the connection was encrypted, CV=,
36246 DN=, and X= items may appear as they do for an incoming message, controlled by
36247 the same logging options.
36249 Finally, if any SMTP commands were issued during the connection, a C= item
36250 is added to the line, listing the commands that were used. For example,
36254 shows that the client issued QUIT straight after EHLO. If there were fewer
36255 than 20 commands, they are all listed. If there were more than 20 commands,
36256 the last 20 are listed, preceded by &"..."&. However, with the default
36257 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
36258 have been aborted before 20 non-mail commands are processed.
36260 &%smtp_mailauth%&: A third subfield with the authenticated sender,
36261 colon-separated, is appended to the A= item for a message arrival or delivery
36262 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
36263 was accepted or used.
36265 .cindex "log" "SMTP protocol error"
36266 .cindex "SMTP" "logging protocol error"
36267 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
36268 encountered. Exim does not have perfect detection of all protocol errors
36269 because of transmission delays and the use of pipelining. If PIPELINING has
36270 been advertised to a client, an Exim server assumes that the client will use
36271 it, and therefore it does not count &"expected"& errors (for example, RCPT
36272 received after rejecting MAIL) as protocol errors.
36274 .cindex "SMTP" "logging syntax errors"
36275 .cindex "SMTP" "syntax errors; logging"
36276 .cindex "SMTP" "unknown command; logging"
36277 .cindex "log" "unknown SMTP command"
36278 .cindex "log" "SMTP syntax error"
36279 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
36280 encountered. An unrecognized command is treated as a syntax error. For an
36281 external connection, the host identity is given; for an internal connection
36282 using &%-bs%& the sender identification (normally the calling user) is given.
36284 .cindex "log" "subject"
36285 .cindex "subject, logging"
36286 &%subject%&: The subject of the message is added to the arrival log line,
36287 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
36288 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
36289 specifies whether characters with values greater than 127 should be logged
36290 unchanged, or whether they should be rendered as escape sequences.
36292 .cindex "log" "certificate verification"
36293 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
36294 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
36295 verified, and &`CV=no`& if not.
36297 .cindex "log" "TLS cipher"
36298 .cindex "TLS" "logging cipher"
36299 &%tls_cipher%&: When a message is sent or received over an encrypted
36300 connection, the cipher suite used is added to the log line, preceded by X=.
36302 .cindex "log" "TLS peer DN"
36303 .cindex "TLS" "logging peer DN"
36304 &%tls_peerdn%&: When a message is sent or received over an encrypted
36305 connection, and a certificate is supplied by the remote host, the peer DN is
36306 added to the log line, preceded by DN=.
36308 .cindex "log" "TLS SNI"
36309 .cindex "TLS" "logging SNI"
36310 &%tls_sni%&: When a message is received over an encrypted connection, and
36311 the remote host provided the Server Name Indication extension, the SNI is
36312 added to the log line, preceded by SNI=.
36314 .cindex "log" "DNS failure in list"
36315 &%unknown_in_list%&: This setting causes a log entry to be written when the
36316 result of a list match is failure because a DNS lookup failed.
36320 .section "Message log" "SECID260"
36321 .cindex "message" "log file for"
36322 .cindex "log" "message log; description of"
36323 .cindex "&_msglog_& directory"
36324 .oindex "&%preserve_message_logs%&"
36325 In addition to the general log files, Exim writes a log file for each message
36326 that it handles. The names of these per-message logs are the message ids, and
36327 they are kept in the &_msglog_& sub-directory of the spool directory. Each
36328 message log contains copies of the log lines that apply to the message. This
36329 makes it easier to inspect the status of an individual message without having
36330 to search the main log. A message log is deleted when processing of the message
36331 is complete, unless &%preserve_message_logs%& is set, but this should be used
36332 only with great care because they can fill up your disk very quickly.
36334 On a heavily loaded system, it may be desirable to disable the use of
36335 per-message logs, in order to reduce disk I/O. This can be done by setting the
36336 &%message_logs%& option false.
36342 . ////////////////////////////////////////////////////////////////////////////
36343 . ////////////////////////////////////////////////////////////////////////////
36345 .chapter "Exim utilities" "CHAPutils"
36346 .scindex IIDutils "utilities"
36347 A number of utility scripts and programs are supplied with Exim and are
36348 described in this chapter. There is also the Exim Monitor, which is covered in
36349 the next chapter. The utilities described here are:
36351 .itable none 0 0 3 7* left 15* left 40* left
36352 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
36353 "list what Exim processes are doing"
36354 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
36355 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
36356 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
36357 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
36359 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
36360 .irow &<<SECTmailstat>>& &'eximstats'& &&&
36361 "extract statistics from the log"
36362 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
36363 "check address acceptance from given IP"
36364 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
36365 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
36366 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
36367 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
36368 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
36369 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
36372 Another utility that might be of use to sites with many MTAs is Tom Kistner's
36373 &'exilog'&. It provides log visualizations across multiple Exim servers. See
36374 &url(http://duncanthrax.net/exilog/) for details.
36379 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
36380 .cindex "&'exiwhat'&"
36381 .cindex "process, querying"
36383 On operating systems that can restart a system call after receiving a signal
36384 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
36385 a line describing what it is doing to the file &_exim-process.info_& in the
36386 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
36387 processes it can find, having first emptied the file. It then waits for one
36388 second to allow the Exim processes to react before displaying the results. In
36389 order to run &'exiwhat'& successfully you have to have sufficient privilege to
36390 send the signal to the Exim processes, so it is normally run as root.
36392 &*Warning*&: This is not an efficient process. It is intended for occasional
36393 use by system administrators. It is not sensible, for example, to set up a
36394 script that sends SIGUSR1 signals to Exim processes at short intervals.
36397 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
36398 varies in different operating systems. Not only are different options used,
36399 but the format of the output is different. For this reason, there are some
36400 system configuration options that configure exactly how &'exiwhat'& works. If
36401 it doesn't seem to be working for you, check the following compile-time
36404 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
36405 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
36406 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
36407 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
36409 An example of typical output from &'exiwhat'& is
36411 164 daemon: -q1h, listening on port 25
36412 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
36413 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
36414 [10.19.42.42] (editor@ref.example)
36415 10592 handling incoming call from [192.168.243.242]
36416 10628 accepting a local non-SMTP message
36418 The first number in the output line is the process number. The third line has
36419 been split here, in order to fit it on the page.
36423 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
36424 .cindex "&'exiqgrep'&"
36425 .cindex "queue" "grepping"
36426 This utility is a Perl script contributed by Matt Hubbard. It runs
36430 or (in case &*-a*& switch is specified)
36434 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
36435 contain alternate exim configuration the queue management might be using.
36437 to obtain a queue listing, and then greps the output to select messages
36438 that match given criteria. The following selection options are available:
36441 .vitem &*-f*&&~<&'regex'&>
36442 Match the sender address using a case-insensitive search. The field that is
36443 tested is enclosed in angle brackets, so you can test for bounce messages with
36447 .vitem &*-r*&&~<&'regex'&>
36448 Match a recipient address using a case-insensitive search. The field that is
36449 tested is not enclosed in angle brackets.
36451 .vitem &*-s*&&~<&'regex'&>
36452 Match against the size field.
36454 .vitem &*-y*&&~<&'seconds'&>
36455 Match messages that are younger than the given time.
36457 .vitem &*-o*&&~<&'seconds'&>
36458 Match messages that are older than the given time.
36461 Match only frozen messages.
36464 Match only non-frozen messages.
36467 The following options control the format of the output:
36471 Display only the count of matching messages.
36474 Long format &-- display the full message information as output by Exim. This is
36478 Display message ids only.
36481 Brief format &-- one line per message.
36484 Display messages in reverse order.
36487 Include delivered recipients in queue listing.
36490 There is one more option, &%-h%&, which outputs a list of options.
36494 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
36495 .cindex "&'exiqsumm'&"
36496 .cindex "queue" "summary"
36497 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
36498 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
36499 running a command such as
36501 exim -bp | exiqsumm
36503 The output consists of one line for each domain that has messages waiting for
36504 it, as in the following example:
36506 3 2322 74m 66m msn.com.example
36508 Each line lists the number of pending deliveries for a domain, their total
36509 volume, and the length of time that the oldest and the newest messages have
36510 been waiting. Note that the number of pending deliveries is greater than the
36511 number of messages when messages have more than one recipient.
36513 A summary line is output at the end. By default the output is sorted on the
36514 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
36515 the output to be sorted by oldest message and by count of messages,
36516 respectively. There are also three options that split the messages for each
36517 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
36518 separates frozen messages, and &%-s%& separates messages according to their
36521 The output of &'exim -bp'& contains the original addresses in the message, so
36522 this also applies to the output from &'exiqsumm'&. No domains from addresses
36523 generated by aliasing or forwarding are included (unless the &%one_time%&
36524 option of the &(redirect)& router has been used to convert them into &"top
36525 level"& addresses).
36530 .section "Extracting specific information from the log (exigrep)" &&&
36532 .cindex "&'exigrep'&"
36533 .cindex "log" "extracts; grepping for"
36534 The &'exigrep'& utility is a Perl script that searches one or more main log
36535 files for entries that match a given pattern. When it finds a match, it
36536 extracts all the log entries for the relevant message, not just those that
36537 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
36538 given message, or all mail for a given user, or for a given host, for example.
36539 The input files can be in Exim log format or syslog format.
36540 If a matching log line is not associated with a specific message, it is
36541 included in &'exigrep'&'s output without any additional lines. The usage is:
36543 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
36545 If no log file names are given on the command line, the standard input is read.
36547 The &%-t%& argument specifies a number of seconds. It adds an additional
36548 condition for message selection. Messages that are complete are shown only if
36549 they spent more than <&'n'&> seconds on the queue.
36551 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
36552 makes it case-sensitive. This may give a performance improvement when searching
36553 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
36554 option; with &%-I%& they do not. In both cases it is possible to change the
36555 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
36557 The &%-l%& option means &"literal"&, that is, treat all characters in the
36558 pattern as standing for themselves. Otherwise the pattern must be a Perl
36559 regular expression.
36561 The &%-v%& option inverts the matching condition. That is, a line is selected
36562 if it does &'not'& match the pattern.
36564 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
36565 that are generated as a result/response to a message that &'exigrep'& matched
36569 user_a sends a message to user_b, which generates a bounce back to user_b. If
36570 &'exigrep'& is used to search for &"user_a"&, only the first message will be
36571 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
36572 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
36573 when searching for &"user_a"& will show both messages since the bounce is
36574 &"related"& to or a &"result"& of the first message that was found by the
36577 If the location of a &'zcat'& command is known from the definition of
36578 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
36579 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
36580 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
36581 autodetection of some well known compression extensions.
36584 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
36585 .cindex "&'exipick'&"
36586 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
36587 lists messages from the queue according to a variety of criteria. For details
36588 of &'exipick'&'s facilities, visit the web page at
36589 &url(http://www.exim.org/eximwiki/ToolExipickManPage) or run &'exipick'& with
36590 the &%--help%& option.
36593 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
36594 .cindex "log" "cycling local files"
36595 .cindex "cycling logs"
36596 .cindex "&'exicyclog'&"
36597 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
36598 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
36599 you are using log files with datestamps in their names (see section
36600 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
36601 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
36602 There are two command line options for &'exicyclog'&:
36604 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
36605 default that is set when Exim is built. The default default is 10.
36607 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
36608 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
36609 overriding the script's default, which is to find the setting from Exim's
36613 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
36614 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
36615 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
36616 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
36617 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
36618 logs are handled similarly.
36620 If the limit is greater than 99, the script uses 3-digit numbers such as
36621 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
36622 to one that is greater, or &'vice versa'&, you will have to fix the names of
36623 any existing log files.
36625 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
36626 the end are deleted. All files with numbers greater than 01 are compressed,
36627 using a compression command which is configured by the COMPRESS_COMMAND
36628 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
36629 root &%crontab%& entry of the form
36631 1 0 * * * su exim -c /usr/exim/bin/exicyclog
36633 assuming you have used the name &"exim"& for the Exim user. You can run
36634 &'exicyclog'& as root if you wish, but there is no need.
36638 .section "Mail statistics (eximstats)" "SECTmailstat"
36639 .cindex "statistics"
36640 .cindex "&'eximstats'&"
36641 A Perl script called &'eximstats'& is provided for extracting statistical
36642 information from log files. The output is either plain text, or HTML.
36643 Exim log files are also supported by the &'Lire'& system produced by the
36644 LogReport Foundation &url(http://www.logreport.org).
36646 The &'eximstats'& script has been hacked about quite a bit over time. The
36647 latest version is the result of some extensive revision by Steve Campbell. A
36648 lot of information is given by default, but there are options for suppressing
36649 various parts of it. Following any options, the arguments to the script are a
36650 list of files, which should be main log files. For example:
36652 eximstats -nr /var/spool/exim/log/mainlog.01
36654 By default, &'eximstats'& extracts information about the number and volume of
36655 messages received from or delivered to various hosts. The information is sorted
36656 both by message count and by volume, and the top fifty hosts in each category
36657 are listed on the standard output. Similar information, based on email
36658 addresses or domains instead of hosts can be requested by means of various
36659 options. For messages delivered and received locally, similar statistics are
36660 also produced per user.
36662 The output also includes total counts and statistics about delivery errors, and
36663 histograms showing the number of messages received and deliveries made in each
36664 hour of the day. A delivery with more than one address in its envelope (for
36665 example, an SMTP transaction with more than one RCPT command) is counted
36666 as a single delivery by &'eximstats'&.
36668 Though normally more deliveries than receipts are reported (as messages may
36669 have multiple recipients), it is possible for &'eximstats'& to report more
36670 messages received than delivered, even though the queue is empty at the start
36671 and end of the period in question. If an incoming message contains no valid
36672 recipients, no deliveries are recorded for it. A bounce message is handled as
36673 an entirely separate message.
36675 &'eximstats'& always outputs a grand total summary giving the volume and number
36676 of messages received and deliveries made, and the number of hosts involved in
36677 each case. It also outputs the number of messages that were delayed (that is,
36678 not completely delivered at the first attempt), and the number that had at
36679 least one address that failed.
36681 The remainder of the output is in sections that can be independently disabled
36682 or modified by various options. It consists of a summary of deliveries by
36683 transport, histograms of messages received and delivered per time interval
36684 (default per hour), information about the time messages spent on the queue,
36685 a list of relayed messages, lists of the top fifty sending hosts, local
36686 senders, destination hosts, and destination local users by count and by volume,
36687 and a list of delivery errors that occurred.
36689 The relay information lists messages that were actually relayed, that is, they
36690 came from a remote host and were directly delivered to some other remote host,
36691 without being processed (for example, for aliasing or forwarding) locally.
36693 There are quite a few options for &'eximstats'& to control exactly what it
36694 outputs. These are documented in the Perl script itself, and can be extracted
36695 by running the command &(perldoc)& on the script. For example:
36697 perldoc /usr/exim/bin/eximstats
36700 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
36701 .cindex "&'exim_checkaccess'&"
36702 .cindex "policy control" "checking access"
36703 .cindex "checking access"
36704 The &%-bh%& command line argument allows you to run a fake SMTP session with
36705 debugging output, in order to check what Exim is doing when it is applying
36706 policy controls to incoming SMTP mail. However, not everybody is sufficiently
36707 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
36708 sometimes you just want to answer the question &"Does this address have
36709 access?"& without bothering with any further details.
36711 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
36712 two arguments, an IP address and an email address:
36714 exim_checkaccess 10.9.8.7 A.User@a.domain.example
36716 The utility runs a call to Exim with the &%-bh%& option, to test whether the
36717 given email address would be accepted in a RCPT command in a TCP/IP
36718 connection from the host with the given IP address. The output of the utility
36719 is either the word &"accepted"&, or the SMTP error response, for example:
36722 550 Relay not permitted
36724 When running this test, the utility uses &`<>`& as the envelope sender address
36725 for the MAIL command, but you can change this by providing additional
36726 options. These are passed directly to the Exim command. For example, to specify
36727 that the test is to be run with the sender address &'himself@there.example'&
36730 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
36731 -f himself@there.example
36733 Note that these additional Exim command line items must be given after the two
36734 mandatory arguments.
36736 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
36737 while running its checks. You can run checks that include callouts by using
36738 &%-bhc%&, but this is not yet available in a &"packaged"& form.
36742 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
36743 .cindex "DBM" "building dbm files"
36744 .cindex "building DBM files"
36745 .cindex "&'exim_dbmbuild'&"
36746 .cindex "lower casing"
36747 .cindex "binary zero" "in lookup key"
36748 The &'exim_dbmbuild'& program reads an input file containing keys and data in
36749 the format used by the &(lsearch)& lookup (see section
36750 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
36751 names as keys and the remainder of the information as data. The lower-casing
36752 can be prevented by calling the program with the &%-nolc%& option.
36754 A terminating zero is included as part of the key string. This is expected by
36755 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
36756 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
36757 strings or the data strings. The &(dbmnz)& lookup type can be used with such
36760 The program requires two arguments: the name of the input file (which can be a
36761 single hyphen to indicate the standard input), and the name of the output file.
36762 It creates the output under a temporary name, and then renames it if all went
36766 If the native DB interface is in use (USE_DB is set in a compile-time
36767 configuration file &-- this is common in free versions of Unix) the two file
36768 names must be different, because in this mode the Berkeley DB functions create
36769 a single output file using exactly the name given. For example,
36771 exim_dbmbuild /etc/aliases /etc/aliases.db
36773 reads the system alias file and creates a DBM version of it in
36774 &_/etc/aliases.db_&.
36776 In systems that use the &'ndbm'& routines (mostly proprietary versions of
36777 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
36778 environment, the suffixes are added to the second argument of
36779 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
36780 when the Berkeley functions are used in compatibility mode (though this is not
36781 recommended), because in that case it adds a &_.db_& suffix to the file name.
36783 If a duplicate key is encountered, the program outputs a warning, and when it
36784 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
36785 option is used. By default, only the first of a set of duplicates is used &--
36786 this makes it compatible with &(lsearch)& lookups. There is an option
36787 &%-lastdup%& which causes it to use the data for the last duplicate instead.
36788 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
36789 &%stderr%&. For other errors, where it doesn't actually make a new file, the
36795 .section "Finding individual retry times (exinext)" "SECTfinindret"
36796 .cindex "retry" "times"
36797 .cindex "&'exinext'&"
36798 A utility called &'exinext'& (mostly a Perl script) provides the ability to
36799 fish specific information out of the retry database. Given a mail domain (or a
36800 complete address), it looks up the hosts for that domain, and outputs any retry
36801 information for the hosts or for the domain. At present, the retry information
36802 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
36803 output. For example:
36805 $ exinext piglet@milne.fict.example
36806 kanga.milne.example:192.168.8.1 error 146: Connection refused
36807 first failed: 21-Feb-1996 14:57:34
36808 last tried: 21-Feb-1996 14:57:34
36809 next try at: 21-Feb-1996 15:02:34
36810 roo.milne.example:192.168.8.3 error 146: Connection refused
36811 first failed: 20-Jan-1996 13:12:08
36812 last tried: 21-Feb-1996 11:42:03
36813 next try at: 21-Feb-1996 19:42:03
36814 past final cutoff time
36816 You can also give &'exinext'& a local part, without a domain, and it
36817 will give any retry information for that local part in your default domain.
36818 A message id can be used to obtain retry information pertaining to a specific
36819 message. This exists only when an attempt to deliver a message to a remote host
36820 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
36821 &'exinext'& is not particularly efficient, but then it is not expected to be
36824 The &'exinext'& utility calls Exim to find out information such as the location
36825 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
36826 passed on to the &'exim'& commands. The first specifies an alternate Exim
36827 configuration file, and the second sets macros for use within the configuration
36828 file. These features are mainly to help in testing, but might also be useful in
36829 environments where more than one configuration file is in use.
36833 .section "Hints database maintenance" "SECThindatmai"
36834 .cindex "hints database" "maintenance"
36835 .cindex "maintaining Exim's hints database"
36836 Three utility programs are provided for maintaining the DBM files that Exim
36837 uses to contain its delivery hint information. Each program requires two
36838 arguments. The first specifies the name of Exim's spool directory, and the
36839 second is the name of the database it is to operate on. These are as follows:
36842 &'retry'&: the database of retry information
36844 &'wait-'&<&'transport name'&>: databases of information about messages waiting
36847 &'callout'&: the callout cache
36849 &'ratelimit'&: the data for implementing the ratelimit ACL condition
36851 &'misc'&: other hints data
36854 The &'misc'& database is used for
36857 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
36859 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
36860 &(smtp)& transport)
36862 Limiting the concurrency of specific transports (when &%max_parallel%& is set
36868 .section "exim_dumpdb" "SECID261"
36869 .cindex "&'exim_dumpdb'&"
36870 The entire contents of a database are written to the standard output by the
36871 &'exim_dumpdb'& program, which has no options or arguments other than the
36872 spool and database names. For example, to dump the retry database:
36874 exim_dumpdb /var/spool/exim retry
36876 Two lines of output are produced for each entry:
36878 T:mail.ref.example:192.168.242.242 146 77 Connection refused
36879 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
36881 The first item on the first line is the key of the record. It starts with one
36882 of the letters R, or T, depending on whether it refers to a routing or
36883 transport retry. For a local delivery, the next part is the local address; for
36884 a remote delivery it is the name of the remote host, followed by its failing IP
36885 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
36886 transport). If the remote port is not the standard one (port 25), it is added
36887 to the IP address. Then there follows an error code, an additional error code,
36888 and a textual description of the error.
36890 The three times on the second line are the time of first failure, the time of
36891 the last delivery attempt, and the computed time for the next attempt. The line
36892 ends with an asterisk if the cutoff time for the last retry rule has been
36895 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
36896 consists of a host name followed by a list of ids for messages that are or were
36897 waiting to be delivered to that host. If there are a very large number for any
36898 one host, continuation records, with a sequence number added to the host name,
36899 may be seen. The data in these records is often out of date, because a message
36900 may be routed to several alternative hosts, and Exim makes no effort to keep
36905 .section "exim_tidydb" "SECID262"
36906 .cindex "&'exim_tidydb'&"
36907 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
36908 database. If run with no options, it removes all records that are more than 30
36909 days old. The age is calculated from the date and time that the record was last
36910 updated. Note that, in the case of the retry database, it is &'not'& the time
36911 since the first delivery failure. Information about a host that has been down
36912 for more than 30 days will remain in the database, provided that the record is
36913 updated sufficiently often.
36915 The cutoff date can be altered by means of the &%-t%& option, which must be
36916 followed by a time. For example, to remove all records older than a week from
36917 the retry database:
36919 exim_tidydb -t 7d /var/spool/exim retry
36921 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
36922 message ids. In the former these appear as data in records keyed by host &--
36923 they were messages that were waiting for that host &-- and in the latter they
36924 are the keys for retry information for messages that have suffered certain
36925 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
36926 message ids in database records are those of messages that are still on the
36927 queue. Message ids for messages that no longer exist are removed from
36928 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
36929 For the &'retry'& database, records whose keys are non-existent message ids are
36930 removed. The &'exim_tidydb'& utility outputs comments on the standard output
36931 whenever it removes information from the database.
36933 Certain records are automatically removed by Exim when they are no longer
36934 needed, but others are not. For example, if all the MX hosts for a domain are
36935 down, a retry record is created for each one. If the primary MX host comes back
36936 first, its record is removed when Exim successfully delivers to it, but the
36937 records for the others remain because Exim has not tried to use those hosts.
36939 It is important, therefore, to run &'exim_tidydb'& periodically on all the
36940 hints databases. You should do this at a quiet time of day, because it requires
36941 a database to be locked (and therefore inaccessible to Exim) while it does its
36942 work. Removing records from a DBM file does not normally make the file smaller,
36943 but all the common DBM libraries are able to re-use the space that is released.
36944 After an initial phase of increasing in size, the databases normally reach a
36945 point at which they no longer get any bigger, as long as they are regularly
36948 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
36949 databases is likely to keep on increasing.
36954 .section "exim_fixdb" "SECID263"
36955 .cindex "&'exim_fixdb'&"
36956 The &'exim_fixdb'& program is a utility for interactively modifying databases.
36957 Its main use is for testing Exim, but it might also be occasionally useful for
36958 getting round problems in a live system. It has no options, and its interface
36959 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
36960 key of a database record can then be entered, and the data for that record is
36963 If &"d"& is typed at the next prompt, the entire record is deleted. For all
36964 except the &'retry'& database, that is the only operation that can be carried
36965 out. For the &'retry'& database, each field is output preceded by a number, and
36966 data for individual fields can be changed by typing the field number followed
36967 by new data, for example:
36971 resets the time of the next delivery attempt. Time values are given as a
36972 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
36973 used as optional separators.
36978 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
36979 .cindex "mailbox" "maintenance"
36980 .cindex "&'exim_lock'&"
36981 .cindex "locking mailboxes"
36982 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
36983 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
36984 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
36985 a user agent while investigating a problem. The utility requires the name of
36986 the file as its first argument. If the locking is successful, the second
36987 argument is run as a command (using C's &[system()]& function); if there is no
36988 second argument, the value of the SHELL environment variable is used; if this
36989 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
36990 is unlocked and the utility ends. The following options are available:
36994 Use &[fcntl()]& locking on the open mailbox.
36997 Use &[flock()]& locking on the open mailbox, provided the operating system
37000 .vitem &%-interval%&
37001 This must be followed by a number, which is a number of seconds; it sets the
37002 interval to sleep between retries (default 3).
37004 .vitem &%-lockfile%&
37005 Create a lock file before opening the mailbox.
37008 Lock the mailbox using MBX rules.
37011 Suppress verification output.
37013 .vitem &%-retries%&
37014 This must be followed by a number; it sets the number of times to try to get
37015 the lock (default 10).
37017 .vitem &%-restore_time%&
37018 This option causes &%exim_lock%& to restore the modified and read times to the
37019 locked file before exiting. This allows you to access a locked mailbox (for
37020 example, to take a backup copy) without disturbing the times that the user
37023 .vitem &%-timeout%&
37024 This must be followed by a number, which is a number of seconds; it sets a
37025 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
37026 default), a non-blocking call is used.
37029 Generate verbose output.
37032 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
37033 default is to create a lock file and also to use &[fcntl()]& locking on the
37034 mailbox, which is the same as Exim's default. The use of &%-flock%& or
37035 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
37036 requires that the directory containing the file be writeable. Locking by lock
37037 file does not last for ever; Exim assumes that a lock file is expired if it is
37038 more than 30 minutes old.
37040 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
37041 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
37042 to be taken out on the open mailbox, and an exclusive lock on the file
37043 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
37044 number of the mailbox file. When the locking is released, if an exclusive lock
37045 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
37047 The default output contains verification of the locking that takes place. The
37048 &%-v%& option causes some additional information to be given. The &%-q%& option
37049 suppresses all output except error messages.
37053 exim_lock /var/spool/mail/spqr
37055 runs an interactive shell while the file is locked, whereas
37057 &`exim_lock -q /var/spool/mail/spqr <<End`&
37058 <&'some commands'&>
37061 runs a specific non-interactive sequence of commands while the file is locked,
37062 suppressing all verification output. A single command can be run by a command
37065 exim_lock -q /var/spool/mail/spqr \
37066 "cp /var/spool/mail/spqr /some/where"
37068 Note that if a command is supplied, it must be entirely contained within the
37069 second argument &-- hence the quotes.
37073 . ////////////////////////////////////////////////////////////////////////////
37074 . ////////////////////////////////////////////////////////////////////////////
37076 .chapter "The Exim monitor" "CHAPeximon"
37077 .scindex IIDeximon "Exim monitor" "description"
37078 .cindex "X-windows"
37079 .cindex "&'eximon'&"
37080 .cindex "Local/eximon.conf"
37081 .cindex "&_exim_monitor/EDITME_&"
37082 The Exim monitor is an application which displays in an X window information
37083 about the state of Exim's queue and what Exim is doing. An admin user can
37084 perform certain operations on messages from this GUI interface; however all
37085 such facilities are also available from the command line, and indeed, the
37086 monitor itself makes use of the command line to perform any actions requested.
37090 .section "Running the monitor" "SECID264"
37091 The monitor is started by running the script called &'eximon'&. This is a shell
37092 script that sets up a number of environment variables, and then runs the
37093 binary called &_eximon.bin_&. The default appearance of the monitor window can
37094 be changed by editing the &_Local/eximon.conf_& file created by editing
37095 &_exim_monitor/EDITME_&. Comments in that file describe what the various
37096 parameters are for.
37098 The parameters that get built into the &'eximon'& script can be overridden for
37099 a particular invocation by setting up environment variables of the same names,
37100 preceded by &`EXIMON_`&. For example, a shell command such as
37102 EXIMON_LOG_DEPTH=400 eximon
37104 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
37105 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
37106 overrides the Exim log file configuration. This makes it possible to have
37107 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
37108 syslog messages are routed to a file on the local host.
37110 X resources can be used to change the appearance of the window in the normal
37111 way. For example, a resource setting of the form
37113 Eximon*background: gray94
37115 changes the colour of the background to light grey rather than white. The
37116 stripcharts are drawn with both the data lines and the reference lines in
37117 black. This means that the reference lines are not visible when on top of the
37118 data. However, their colour can be changed by setting a resource called
37119 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
37120 For example, if your X server is running Unix, you could set up lighter
37121 reference lines in the stripcharts by obeying
37124 Eximon*highlight: gray
37127 .cindex "admin user"
37128 In order to see the contents of messages on the queue, and to operate on them,
37129 &'eximon'& must either be run as root or by an admin user.
37131 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
37132 contain X11 resource parameters interpreted by the X11 library. In addition,
37133 if the first parameter starts with the string "gdb" then it is removed and the
37134 binary is invoked under gdb (the parameter is used as the gdb command-name, so
37135 versioned variants of gdb can be invoked).
37137 The monitor's window is divided into three parts. The first contains one or
37138 more stripcharts and two action buttons, the second contains a &"tail"& of the
37139 main log file, and the third is a display of the queue of messages awaiting
37140 delivery, with two more action buttons. The following sections describe these
37141 different parts of the display.
37146 .section "The stripcharts" "SECID265"
37147 .cindex "stripchart"
37148 The first stripchart is always a count of messages on the queue. Its name can
37149 be configured by setting QUEUE_STRIPCHART_NAME in the
37150 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
37151 configuration script by regular expression matches on log file entries, making
37152 it possible to display, for example, counts of messages delivered to certain
37153 hosts or using certain transports. The supplied defaults display counts of
37154 received and delivered messages, and of local and SMTP deliveries. The default
37155 period between stripchart updates is one minute; this can be adjusted by a
37156 parameter in the &_Local/eximon.conf_& file.
37158 The stripchart displays rescale themselves automatically as the value they are
37159 displaying changes. There are always 10 horizontal lines in each chart; the
37160 title string indicates the value of each division when it is greater than one.
37161 For example, &"x2"& means that each division represents a value of 2.
37163 It is also possible to have a stripchart which shows the percentage fullness of
37164 a particular disk partition, which is useful when local deliveries are confined
37165 to a single partition.
37167 .cindex "&%statvfs%& function"
37168 This relies on the availability of the &[statvfs()]& function or equivalent in
37169 the operating system. Most, but not all versions of Unix that support Exim have
37170 this. For this particular stripchart, the top of the chart always represents
37171 100%, and the scale is given as &"x10%"&. This chart is configured by setting
37172 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
37173 &_Local/eximon.conf_& file.
37178 .section "Main action buttons" "SECID266"
37179 .cindex "size" "of monitor window"
37180 .cindex "Exim monitor" "window size"
37181 .cindex "window size"
37182 Below the stripcharts there is an action button for quitting the monitor. Next
37183 to this is another button marked &"Size"&. They are placed here so that
37184 shrinking the window to its default minimum size leaves just the queue count
37185 stripchart and these two buttons visible. Pressing the &"Size"& button causes
37186 the window to expand to its maximum size, unless it is already at the maximum,
37187 in which case it is reduced to its minimum.
37189 When expanding to the maximum, if the window cannot be fully seen where it
37190 currently is, it is moved back to where it was the last time it was at full
37191 size. When it is expanding from its minimum size, the old position is
37192 remembered, and next time it is reduced to the minimum it is moved back there.
37194 The idea is that you can keep a reduced window just showing one or two
37195 stripcharts at a convenient place on your screen, easily expand it to show
37196 the full window when required, and just as easily put it back to what it was.
37197 The idea is copied from what the &'twm'& window manager does for its
37198 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
37199 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
37201 Normally, the monitor starts up with the window at its full size, but it can be
37202 built so that it starts up with the window at its smallest size, by setting
37203 START_SMALL=yes in &_Local/eximon.conf_&.
37207 .section "The log display" "SECID267"
37208 .cindex "log" "tail of; in monitor"
37209 The second section of the window is an area in which a display of the tail of
37210 the main log is maintained.
37211 To save space on the screen, the timestamp on each log line is shortened by
37212 removing the date and, if &%log_timezone%& is set, the timezone.
37213 The log tail is not available when the only destination for logging data is
37214 syslog, unless the syslog lines are routed to a local file whose name is passed
37215 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
37217 The log sub-window has a scroll bar at its lefthand side which can be used to
37218 move back to look at earlier text, and the up and down arrow keys also have a
37219 scrolling effect. The amount of log that is kept depends on the setting of
37220 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
37221 to use. When this is full, the earlier 50% of data is discarded &-- this is
37222 much more efficient than throwing it away line by line. The sub-window also has
37223 a horizontal scroll bar for accessing the ends of long log lines. This is the
37224 only means of horizontal scrolling; the right and left arrow keys are not
37225 available. Text can be cut from this part of the window using the mouse in the
37226 normal way. The size of this subwindow is controlled by parameters in the
37227 configuration file &_Local/eximon.conf_&.
37229 Searches of the text in the log window can be carried out by means of the ^R
37230 and ^S keystrokes, which default to a reverse and a forward search,
37231 respectively. The search covers only the text that is displayed in the window.
37232 It cannot go further back up the log.
37234 The point from which the search starts is indicated by a caret marker. This is
37235 normally at the end of the text in the window, but can be positioned explicitly
37236 by pointing and clicking with the left mouse button, and is moved automatically
37237 by a successful search. If new text arrives in the window when it is scrolled
37238 back, the caret remains where it is, but if the window is not scrolled back,
37239 the caret is moved to the end of the new text.
37241 Pressing ^R or ^S pops up a window into which the search text can be typed.
37242 There are buttons for selecting forward or reverse searching, for carrying out
37243 the search, and for cancelling. If the &"Search"& button is pressed, the search
37244 happens and the window remains so that further searches can be done. If the
37245 &"Return"& key is pressed, a single search is done and the window is closed. If
37246 ^C is typed the search is cancelled.
37248 The searching facility is implemented using the facilities of the Athena text
37249 widget. By default this pops up a window containing both &"search"& and
37250 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
37251 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
37252 However, the linkers in BSDI and HP-UX seem unable to handle an externally
37253 provided version of &%TextPop%& when the remaining parts of the text widget
37254 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
37255 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
37256 on these systems, at the expense of having unwanted items in the search popup
37261 .section "The queue display" "SECID268"
37262 .cindex "queue" "display in monitor"
37263 The bottom section of the monitor window contains a list of all messages that
37264 are on the queue, which includes those currently being received or delivered,
37265 as well as those awaiting delivery. The size of this subwindow is controlled by
37266 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
37267 at which it is updated is controlled by another parameter in the same file &--
37268 the default is 5 minutes, since queue scans can be quite expensive. However,
37269 there is an &"Update"& action button just above the display which can be used
37270 to force an update of the queue display at any time.
37272 When a host is down for some time, a lot of pending mail can build up for it,
37273 and this can make it hard to deal with other messages on the queue. To help
37274 with this situation there is a button next to &"Update"& called &"Hide"&. If
37275 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
37276 type anything in here and press &"Return"&, the text is added to a chain of
37277 such texts, and if every undelivered address in a message matches at least one
37278 of the texts, the message is not displayed.
37280 If there is an address that does not match any of the texts, all the addresses
37281 are displayed as normal. The matching happens on the ends of addresses so, for
37282 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
37283 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
37284 has been set up, a button called &"Unhide"& is displayed. If pressed, it
37285 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
37286 a hide request is automatically cancelled after one hour.
37288 While the dialogue box is displayed, you can't press any buttons or do anything
37289 else to the monitor window. For this reason, if you want to cut text from the
37290 queue display to use in the dialogue box, you have to do the cutting before
37291 pressing the &"Hide"& button.
37293 The queue display contains, for each unhidden queued message, the length of
37294 time it has been on the queue, the size of the message, the message id, the
37295 message sender, and the first undelivered recipient, all on one line. If it is
37296 a bounce message, the sender is shown as &"<>"&. If there is more than one
37297 recipient to which the message has not yet been delivered, subsequent ones are
37298 listed on additional lines, up to a maximum configured number, following which
37299 an ellipsis is displayed. Recipients that have already received the message are
37302 .cindex "frozen messages" "display"
37303 If a message is frozen, an asterisk is displayed at the left-hand side.
37305 The queue display has a vertical scroll bar, and can also be scrolled by means
37306 of the arrow keys. Text can be cut from it using the mouse in the normal way.
37307 The text searching facilities, as described above for the log window, are also
37308 available, but the caret is always moved to the end of the text when the queue
37309 display is updated.
37313 .section "The queue menu" "SECID269"
37314 .cindex "queue" "menu in monitor"
37315 If the &%shift%& key is held down and the left button is clicked when the mouse
37316 pointer is over the text for any message, an action menu pops up, and the first
37317 line of the queue display for the message is highlighted. This does not affect
37320 If you want to use some other event for popping up the menu, you can set the
37321 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
37322 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
37323 value set in this parameter is a standard X event description. For example, to
37324 run eximon using &%ctrl%& rather than &%shift%& you could use
37326 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
37328 The title of the menu is the message id, and it contains entries which act as
37332 &'message log'&: The contents of the message log for the message are displayed
37333 in a new text window.
37335 &'headers'&: Information from the spool file that contains the envelope
37336 information and headers is displayed in a new text window. See chapter
37337 &<<CHAPspool>>& for a description of the format of spool files.
37339 &'body'&: The contents of the spool file containing the body of the message are
37340 displayed in a new text window. There is a default limit of 20,000 bytes to the
37341 amount of data displayed. This can be changed by setting the BODY_MAX
37342 option at compile time, or the EXIMON_BODY_MAX option at run time.
37344 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
37345 delivery of the message. This causes an automatic thaw if the message is
37346 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
37347 a new text window. The delivery is run in a separate process, to avoid holding
37348 up the monitor while the delivery proceeds.
37350 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
37351 that the message be frozen.
37353 .cindex "thawing messages"
37354 .cindex "unfreezing messages"
37355 .cindex "frozen messages" "thawing"
37356 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
37357 that the message be thawed.
37359 .cindex "delivery" "forcing failure"
37360 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
37361 that Exim gives up trying to deliver the message. A bounce message is generated
37362 for any remaining undelivered addresses.
37364 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
37365 that the message be deleted from the system without generating a bounce
37368 &'add recipient'&: A dialog box is displayed into which a recipient address can
37369 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37370 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37371 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37372 causes a call to Exim to be made using the &%-Mar%& option to request that an
37373 additional recipient be added to the message, unless the entry box is empty, in
37374 which case no action is taken.
37376 &'mark delivered'&: A dialog box is displayed into which a recipient address
37377 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
37378 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
37379 Otherwise it must be entered as a fully qualified address. Pressing RETURN
37380 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
37381 recipient address as already delivered, unless the entry box is empty, in which
37382 case no action is taken.
37384 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
37385 mark all recipient addresses as already delivered.
37387 &'edit sender'&: A dialog box is displayed initialized with the current
37388 sender's address. Pressing RETURN causes a call to Exim to be made using the
37389 &%-Mes%& option to replace the sender address, unless the entry box is empty,
37390 in which case no action is taken. If you want to set an empty sender (as in
37391 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
37392 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
37393 the address is qualified with that domain.
37396 When a delivery is forced, a window showing the &%-v%& output is displayed. In
37397 other cases when a call to Exim is made, if there is any output from Exim (in
37398 particular, if the command fails) a window containing the command and the
37399 output is displayed. Otherwise, the results of the action are normally apparent
37400 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
37401 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
37402 if no output is generated.
37404 The queue display is automatically updated for actions such as freezing and
37405 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
37406 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
37407 force an update of the display after one of these actions.
37409 In any text window that is displayed as result of a menu action, the normal
37410 cut-and-paste facility is available, and searching can be carried out using ^R
37411 and ^S, as described above for the log tail window.
37418 . ////////////////////////////////////////////////////////////////////////////
37419 . ////////////////////////////////////////////////////////////////////////////
37421 .chapter "Security considerations" "CHAPsecurity"
37422 .scindex IIDsecurcon "security" "discussion of"
37423 This chapter discusses a number of issues concerned with security, some of
37424 which are also covered in other parts of this manual.
37426 For reasons that this author does not understand, some people have promoted
37427 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
37428 existence of this chapter in the documentation. However, the intent of the
37429 chapter is simply to describe the way Exim works in relation to certain
37430 security concerns, not to make any specific claims about the effectiveness of
37431 its security as compared with other MTAs.
37433 What follows is a description of the way Exim is supposed to be. Best efforts
37434 have been made to try to ensure that the code agrees with the theory, but an
37435 absence of bugs can never be guaranteed. Any that are reported will get fixed
37436 as soon as possible.
37439 .section "Building a more &""hardened""& Exim" "SECID286"
37440 .cindex "security" "build-time features"
37441 There are a number of build-time options that can be set in &_Local/Makefile_&
37442 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
37443 Exim administrator who does not have the root password, or by someone who has
37444 penetrated the Exim (but not the root) account. These options are as follows:
37447 ALT_CONFIG_PREFIX can be set to a string that is required to match the
37448 start of any file names used with the &%-C%& option. When it is set, these file
37449 names are also not allowed to contain the sequence &"/../"&. (However, if the
37450 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
37451 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
37452 default setting for &%ALT_CONFIG_PREFIX%&.
37454 If the permitted configuration files are confined to a directory to
37455 which only root has access, this guards against someone who has broken
37456 into the Exim account from running a privileged Exim with an arbitrary
37457 configuration file, and using it to break into other accounts.
37460 If a non-trusted configuration file (i.e. not the default configuration file
37461 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
37462 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
37463 the next item), then root privilege is retained only if the caller of Exim is
37464 root. This locks out the possibility of testing a configuration using &%-C%&
37465 right through message reception and delivery, even if the caller is root. The
37466 reception works, but by that time, Exim is running as the Exim user, so when
37467 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
37468 privilege to be lost. However, root can test reception and delivery using two
37472 The WHITELIST_D_MACROS build option declares some macros to be safe to override
37473 with &%-D%& if the real uid is one of root, the Exim run-time user or the
37474 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
37475 requiring the run-time value supplied to &%-D%& to match a regex that errs on
37476 the restrictive side. Requiring build-time selection of safe macros is onerous
37477 but this option is intended solely as a transition mechanism to permit
37478 previously-working configurations to continue to work after release 4.73.
37480 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
37483 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
37484 never to be used for any deliveries. This is like the &%never_users%& runtime
37485 option, but it cannot be overridden; the runtime option adds additional users
37486 to the list. The default setting is &"root"&; this prevents a non-root user who
37487 is permitted to modify the runtime file from using Exim as a way to get root.
37492 .section "Root privilege" "SECID270"
37494 .cindex "root privilege"
37495 The Exim binary is normally setuid to root, which means that it gains root
37496 privilege (runs as root) when it starts execution. In some special cases (for
37497 example, when the daemon is not in use and there are no local deliveries), it
37498 may be possible to run Exim setuid to some user other than root. This is
37499 discussed in the next section. However, in most installations, root privilege
37500 is required for two things:
37503 To set up a socket connected to the standard SMTP port (25) when initialising
37504 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
37507 To be able to change uid and gid in order to read users' &_.forward_& files and
37508 perform local deliveries as the receiving user or as specified in the
37512 It is not necessary to be root to do any of the other things Exim does, such as
37513 receiving messages and delivering them externally over SMTP, and it is
37514 obviously more secure if Exim does not run as root except when necessary.
37515 For this reason, a user and group for Exim to use must be defined in
37516 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
37517 group"&. Their values can be changed by the run time configuration, though this
37518 is not recommended. Often a user called &'exim'& is used, but some sites use
37519 &'mail'& or another user name altogether.
37521 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
37522 abdication; the process cannot regain root afterwards. Prior to release 4.00,
37523 &[seteuid()]& was used in some circumstances, but this is no longer the case.
37525 After a new Exim process has interpreted its command line options, it changes
37526 uid and gid in the following cases:
37531 If the &%-C%& option is used to specify an alternate configuration file, or if
37532 the &%-D%& option is used to define macro values for the configuration, and the
37533 calling process is not running as root, the uid and gid are changed to those of
37534 the calling process.
37535 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
37536 option may not be used at all.
37537 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
37538 can be supplied if the calling process is running as root, the Exim run-time
37539 user or CONFIGURE_OWNER, if defined.
37544 If the expansion test option (&%-be%&) or one of the filter testing options
37545 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
37548 If the process is not a daemon process or a queue runner process or a delivery
37549 process or a process for testing address routing (started with &%-bt%&), the
37550 uid and gid are changed to the Exim user and group. This means that Exim always
37551 runs under its own uid and gid when receiving messages. This also applies when
37552 testing address verification
37555 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
37558 For a daemon, queue runner, delivery, or address testing process, the uid
37559 remains as root at this stage, but the gid is changed to the Exim group.
37562 The processes that initially retain root privilege behave as follows:
37565 A daemon process changes the gid to the Exim group and the uid to the Exim
37566 user after setting up one or more listening sockets. The &[initgroups()]&
37567 function is called, so that if the Exim user is in any additional groups, they
37568 will be used during message reception.
37570 A queue runner process retains root privilege throughout its execution. Its
37571 job is to fork a controlled sequence of delivery processes.
37573 A delivery process retains root privilege throughout most of its execution,
37574 but any actual deliveries (that is, the transports themselves) are run in
37575 subprocesses which always change to a non-root uid and gid. For local
37576 deliveries this is typically the uid and gid of the owner of the mailbox; for
37577 remote deliveries, the Exim uid and gid are used. Once all the delivery
37578 subprocesses have been run, a delivery process changes to the Exim uid and gid
37579 while doing post-delivery tidying up such as updating the retry database and
37580 generating bounce and warning messages.
37582 While the recipient addresses in a message are being routed, the delivery
37583 process runs as root. However, if a user's filter file has to be processed,
37584 this is done in a subprocess that runs under the individual user's uid and
37585 gid. A system filter is run as root unless &%system_filter_user%& is set.
37587 A process that is testing addresses (the &%-bt%& option) runs as root so that
37588 the routing is done in the same environment as a message delivery.
37594 .section "Running Exim without privilege" "SECTrunexiwitpri"
37595 .cindex "privilege, running without"
37596 .cindex "unprivileged running"
37597 .cindex "root privilege" "running without"
37598 Some installations like to run Exim in an unprivileged state for more of its
37599 operation, for added security. Support for this mode of operation is provided
37600 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
37601 gid are changed to the Exim user and group at the start of a delivery process
37602 (and also queue runner and address testing processes). This means that address
37603 routing is no longer run as root, and the deliveries themselves cannot change
37607 .cindex "daemon" "restarting"
37608 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
37609 that the daemon can still be started in the usual way, and it can respond
37610 correctly to SIGHUP because the re-invocation regains root privilege.
37612 An alternative approach is to make Exim setuid to the Exim user and also setgid
37613 to the Exim group. If you do this, the daemon must be started from a root
37614 process. (Calling Exim from a root process makes it behave in the way it does
37615 when it is setuid root.) However, the daemon cannot restart itself after a
37616 SIGHUP signal because it cannot regain privilege.
37618 It is still useful to set &%deliver_drop_privilege%& in this case, because it
37619 stops Exim from trying to re-invoke itself to do a delivery after a message has
37620 been received. Such a re-invocation is a waste of resources because it has no
37623 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
37624 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
37625 to the Exim user seems a clean approach, but there is one complication:
37627 In this style of operation, Exim is running with the real uid and gid set to
37628 those of the calling process, and the effective uid/gid set to Exim's values.
37629 Ideally, any association with the calling process' uid/gid should be dropped,
37630 that is, the real uid/gid should be reset to the effective values so as to
37631 discard any privileges that the caller may have. While some operating systems
37632 have a function that permits this action for a non-root effective uid, quite a
37633 number of them do not. Because of this lack of standardization, Exim does not
37634 address this problem at this time.
37636 For this reason, the recommended approach for &"mostly unprivileged"& running
37637 is to keep the Exim binary setuid to root, and to set
37638 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
37639 be used in the most straightforward way.
37641 If you configure Exim not to run delivery processes as root, there are a
37642 number of restrictions on what you can do:
37645 You can deliver only as the Exim user/group. You should explicitly use the
37646 &%user%& and &%group%& options to override routers or local transports that
37647 normally deliver as the recipient. This makes sure that configurations that
37648 work in this mode function the same way in normal mode. Any implicit or
37649 explicit specification of another user causes an error.
37651 Use of &_.forward_& files is severely restricted, such that it is usually
37652 not worthwhile to include them in the configuration.
37654 Users who wish to use &_.forward_& would have to make their home directory and
37655 the file itself accessible to the Exim user. Pipe and append-to-file entries,
37656 and their equivalents in Exim filters, cannot be used. While they could be
37657 enabled in the Exim user's name, that would be insecure and not very useful.
37659 Unless the local user mailboxes are all owned by the Exim user (possible in
37660 some POP3 or IMAP-only environments):
37663 They must be owned by the Exim group and be writeable by that group. This
37664 implies you must set &%mode%& in the appendfile configuration, as well as the
37665 mode of the mailbox files themselves.
37667 You must set &%no_check_owner%&, since most or all of the files will not be
37668 owned by the Exim user.
37670 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
37671 on a newly created mailbox when unprivileged. This also implies that new
37672 mailboxes need to be created manually.
37677 These restrictions severely restrict what can be done in local deliveries.
37678 However, there are no restrictions on remote deliveries. If you are running a
37679 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
37680 gives more security at essentially no cost.
37682 If you are using the &%mua_wrapper%& facility (see chapter
37683 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
37688 .section "Delivering to local files" "SECID271"
37689 Full details of the checks applied by &(appendfile)& before it writes to a file
37690 are given in chapter &<<CHAPappendfile>>&.
37694 .section "Running local commands" "SECTsecconslocalcmds"
37695 .cindex "security" "local commands"
37696 .cindex "security" "command injection attacks"
37697 There are a number of ways in which an administrator can configure Exim to run
37698 commands based upon received, untrustworthy, data. Further, in some
37699 configurations a user who can control a &_.forward_& file can also arrange to
37700 run commands. Configuration to check includes, but is not limited to:
37703 Use of &%use_shell%& in the pipe transport: various forms of shell command
37704 injection may be possible with this option present. It is dangerous and should
37705 be used only with considerable caution. Consider constraints which whitelist
37706 allowed characters in a variable which is to be used in a pipe transport that
37707 has &%use_shell%& enabled.
37709 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
37710 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
37711 &_.forward_& files in a redirect router. If Exim is running on a central mail
37712 hub to which ordinary users do not have shell access, but home directories are
37713 NFS mounted (for instance) then administrators should review the list of these
37714 forbid options available, and should bear in mind that the options that may
37715 need forbidding can change as new features are added between releases.
37717 The &%${run...}%& expansion item does not use a shell by default, but
37718 administrators can configure use of &_/bin/sh_& as part of the command.
37719 Such invocations should be viewed with prejudicial suspicion.
37721 Administrators who use embedded Perl are advised to explore how Perl's
37722 taint checking might apply to their usage.
37724 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
37725 administrators are well advised to view its use with suspicion, in case (for
37726 instance) it allows a local-part to contain embedded Exim directives.
37728 Use of &%${match_local_part...}%& and friends becomes more dangerous if
37729 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
37730 each can reference arbitrary lists and files, rather than just being a list
37732 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
37733 real-world security vulnerabilities caused by its use with untrustworthy data
37734 injected in, for SQL injection attacks.
37735 Consider the use of the &%inlisti%& expansion condition instead.
37741 .section "Trust in configuration data" "SECTsecconfdata"
37742 .cindex "security" "data sources"
37743 .cindex "security" "regular expressions"
37744 .cindex "regular expressions" "security"
37745 .cindex "PCRE" "security"
37746 If configuration data for Exim can come from untrustworthy sources, there
37747 are some issues to be aware of:
37750 Use of &%${expand...}%& may provide a path for shell injection attacks.
37752 Letting untrusted data provide a regular expression is unwise.
37754 Using &%${match...}%& to apply a fixed regular expression against untrusted
37755 data may result in pathological behaviour within PCRE. Be aware of what
37756 "backtracking" means and consider options for being more strict with a regular
37757 expression. Avenues to explore include limiting what can match (avoiding &`.`&
37758 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
37759 possessive quantifiers or just not using regular expressions against untrusted
37762 It can be important to correctly use &%${quote:...}%&,
37763 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
37764 items to ensure that data is correctly constructed.
37766 Some lookups might return multiple results, even though normal usage is only
37767 expected to yield one result.
37773 .section "IPv4 source routing" "SECID272"
37774 .cindex "source routing" "in IP packets"
37775 .cindex "IP source routing"
37776 Many operating systems suppress IP source-routed packets in the kernel, but
37777 some cannot be made to do this, so Exim does its own check. It logs incoming
37778 IPv4 source-routed TCP calls, and then drops them. Things are all different in
37779 IPv6. No special checking is currently done.
37783 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
37784 Support for these SMTP commands is disabled by default. If required, they can
37785 be enabled by defining suitable ACLs.
37790 .section "Privileged users" "SECID274"
37791 .cindex "trusted users"
37792 .cindex "admin user"
37793 .cindex "privileged user"
37794 .cindex "user" "trusted"
37795 .cindex "user" "admin"
37796 Exim recognizes two sets of users with special privileges. Trusted users are
37797 able to submit new messages to Exim locally, but supply their own sender
37798 addresses and information about a sending host. For other users submitting
37799 local messages, Exim sets up the sender address from the uid, and doesn't
37800 permit a remote host to be specified.
37803 However, an untrusted user is permitted to use the &%-f%& command line option
37804 in the special form &%-f <>%& to indicate that a delivery failure for the
37805 message should not cause an error report. This affects the message's envelope,
37806 but it does not affect the &'Sender:'& header. Untrusted users may also be
37807 permitted to use specific forms of address with the &%-f%& option by setting
37808 the &%untrusted_set_sender%& option.
37810 Trusted users are used to run processes that receive mail messages from some
37811 other mail domain and pass them on to Exim for delivery either locally, or over
37812 the Internet. Exim trusts a caller that is running as root, as the Exim user,
37813 as any user listed in the &%trusted_users%& configuration option, or under any
37814 group listed in the &%trusted_groups%& option.
37816 Admin users are permitted to do things to the messages on Exim's queue. They
37817 can freeze or thaw messages, cause them to be returned to their senders, remove
37818 them entirely, or modify them in various ways. In addition, admin users can run
37819 the Exim monitor and see all the information it is capable of providing, which
37820 includes the contents of files on the spool.
37824 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
37825 delivery of messages on its queue is restricted to admin users. This
37826 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
37827 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
37828 queue is also restricted to admin users. This restriction can be relaxed by
37829 setting &%no_queue_list_requires_admin%&.
37831 Exim recognizes an admin user if the calling process is running as root or as
37832 the Exim user or if any of the groups associated with the calling process is
37833 the Exim group. It is not necessary actually to be running under the Exim
37834 group. However, if admin users who are not root or the Exim user are to access
37835 the contents of files on the spool via the Exim monitor (which runs
37836 unprivileged), Exim must be built to allow group read access to its spool
37841 .section "Spool files" "SECID275"
37842 .cindex "spool directory" "files"
37843 Exim's spool directory and everything it contains is owned by the Exim user and
37844 set to the Exim group. The mode for spool files is defined in the
37845 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
37846 any user who is a member of the Exim group can access these files.
37850 .section "Use of argv[0]" "SECID276"
37851 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
37852 of specific strings, Exim assumes certain options. For example, calling Exim
37853 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
37854 to calling it with the option &%-bS%&. There are no security implications in
37859 .section "Use of %f formatting" "SECID277"
37860 The only use made of &"%f"& by Exim is in formatting load average values. These
37861 are actually stored in integer variables as 1000 times the load average.
37862 Consequently, their range is limited and so therefore is the length of the
37867 .section "Embedded Exim path" "SECID278"
37868 Exim uses its own path name, which is embedded in the code, only when it needs
37869 to re-exec in order to regain root privilege. Therefore, it is not root when it
37870 does so. If some bug allowed the path to get overwritten, it would lead to an
37871 arbitrary program's being run as exim, not as root.
37875 .section "Dynamic module directory" "SECTdynmoddir"
37876 Any dynamically loadable modules must be installed into the directory
37877 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
37881 .section "Use of sprintf()" "SECID279"
37882 .cindex "&[sprintf()]&"
37883 A large number of occurrences of &"sprintf"& in the code are actually calls to
37884 &'string_sprintf()'&, a function that returns the result in malloc'd store.
37885 The intermediate formatting is done into a large fixed buffer by a function
37886 that runs through the format string itself, and checks the length of each
37887 conversion before performing it, thus preventing buffer overruns.
37889 The remaining uses of &[sprintf()]& happen in controlled circumstances where
37890 the output buffer is known to be sufficiently long to contain the converted
37895 .section "Use of debug_printf() and log_write()" "SECID280"
37896 Arbitrary strings are passed to both these functions, but they do their
37897 formatting by calling the function &'string_vformat()'&, which runs through
37898 the format string itself, and checks the length of each conversion.
37902 .section "Use of strcat() and strcpy()" "SECID281"
37903 These are used only in cases where the output buffer is known to be large
37904 enough to hold the result.
37905 .ecindex IIDsecurcon
37910 . ////////////////////////////////////////////////////////////////////////////
37911 . ////////////////////////////////////////////////////////////////////////////
37913 .chapter "Format of spool files" "CHAPspool"
37914 .scindex IIDforspo1 "format" "spool files"
37915 .scindex IIDforspo2 "spool directory" "format of files"
37916 .scindex IIDforspo3 "spool files" "format of"
37917 .cindex "spool files" "editing"
37918 A message on Exim's queue consists of two files, whose names are the message id
37919 followed by -D and -H, respectively. The data portion of the message is kept in
37920 the -D file on its own. The message's envelope, status, and headers are all
37921 kept in the -H file, whose format is described in this chapter. Each of these
37922 two files contains the final component of its own name as its first line. This
37923 is insurance against disk crashes where the directory is lost but the files
37924 themselves are recoverable.
37926 Some people are tempted into editing -D files in order to modify messages. You
37927 need to be extremely careful if you do this; it is not recommended and you are
37928 on your own if you do it. Here are some of the pitfalls:
37931 You must ensure that Exim does not try to deliver the message while you are
37932 fiddling with it. The safest way is to take out a write lock on the -D file,
37933 which is what Exim itself does, using &[fcntl()]&. If you update the file in
37934 place, the lock will be retained. If you write a new file and rename it, the
37935 lock will be lost at the instant of rename.
37937 .vindex "&$body_linecount$&"
37938 If you change the number of lines in the file, the value of
37939 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
37940 cause incomplete transmission of messages or undeliverable messages.
37942 If the message is in MIME format, you must take care not to break it.
37944 If the message is cryptographically signed, any change will invalidate the
37947 All in all, modifying -D files is fraught with danger.
37949 Files whose names end with -J may also be seen in the &_input_& directory (or
37950 its subdirectories when &%split_spool_directory%& is set). These are journal
37951 files, used to record addresses to which the message has been delivered during
37952 the course of a delivery attempt. If there are still undelivered recipients at
37953 the end, the -H file is updated, and the -J file is deleted. If, however, there
37954 is some kind of crash (for example, a power outage) before this happens, the -J
37955 file remains in existence. When Exim next processes the message, it notices the
37956 -J file and uses it to update the -H file before starting the next delivery
37959 .section "Format of the -H file" "SECID282"
37960 .cindex "uid (user id)" "in spool file"
37961 .cindex "gid (group id)" "in spool file"
37962 The second line of the -H file contains the login name for the uid of the
37963 process that called Exim to read the message, followed by the numerical uid and
37964 gid. For a locally generated message, this is normally the user who sent the
37965 message. For a message received over TCP/IP via the daemon, it is
37966 normally the Exim user.
37968 The third line of the file contains the address of the message's sender as
37969 transmitted in the envelope, contained in angle brackets. The sender address is
37970 empty for bounce messages. For incoming SMTP mail, the sender address is given
37971 in the MAIL command. For locally generated mail, the sender address is
37972 created by Exim from the login name of the current user and the configured
37973 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
37974 leading &"From&~"& line if the caller is trusted, or if the supplied address is
37975 &"<>"& or an address that matches &%untrusted_set_senders%&.
37977 The fourth line contains two numbers. The first is the time that the message
37978 was received, in the conventional Unix form &-- the number of seconds since the
37979 start of the epoch. The second number is a count of the number of messages
37980 warning of delayed delivery that have been sent to the sender.
37982 There follow a number of lines starting with a hyphen. These can appear in any
37983 order, and are omitted when not relevant:
37986 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
37987 This item is obsolete, and is not generated from Exim release 4.61 onwards;
37988 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
37989 recognized, to provide backward compatibility. In the old format, a line of
37990 this form is present for every ACL variable that is not empty. The number
37991 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
37992 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
37993 the data string for the variable. The string itself starts at the beginning of
37994 the next line, and is followed by a newline character. It may contain internal
37997 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
37998 A line of this form is present for every ACL connection variable that is
37999 defined. Note that there is a space between &%-aclc%& and the rest of the name.
38000 The length is the length of the data string for the variable. The string itself
38001 starts at the beginning of the next line, and is followed by a newline
38002 character. It may contain internal newlines.
38004 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
38005 A line of this form is present for every ACL message variable that is defined.
38006 Note that there is a space between &%-aclm%& and the rest of the name. The
38007 length is the length of the data string for the variable. The string itself
38008 starts at the beginning of the next line, and is followed by a newline
38009 character. It may contain internal newlines.
38011 .vitem "&%-active_hostname%&&~<&'hostname'&>"
38012 This is present if, when the message was received over SMTP, the value of
38013 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
38015 .vitem &%-allow_unqualified_recipient%&
38016 This is present if unqualified recipient addresses are permitted in header
38017 lines (to stop such addresses from being qualified if rewriting occurs at
38018 transport time). Local messages that were input using &%-bnq%& and remote
38019 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
38021 .vitem &%-allow_unqualified_sender%&
38022 This is present if unqualified sender addresses are permitted in header lines
38023 (to stop such addresses from being qualified if rewriting occurs at transport
38024 time). Local messages that were input using &%-bnq%& and remote messages from
38025 hosts that match &%sender_unqualified_hosts%& set this flag.
38027 .vitem "&%-auth_id%&&~<&'text'&>"
38028 The id information for a message received on an authenticated SMTP connection
38029 &-- the value of the &$authenticated_id$& variable.
38031 .vitem "&%-auth_sender%&&~<&'address'&>"
38032 The address of an authenticated sender &-- the value of the
38033 &$authenticated_sender$& variable.
38035 .vitem "&%-body_linecount%&&~<&'number'&>"
38036 This records the number of lines in the body of the message, and is always
38039 .vitem "&%-body_zerocount%&&~<&'number'&>"
38040 This records the number of binary zero bytes in the body of the message, and is
38041 present if the number is greater than zero.
38043 .vitem &%-deliver_firsttime%&
38044 This is written when a new message is first added to the spool. When the spool
38045 file is updated after a deferral, it is omitted.
38047 .vitem "&%-frozen%&&~<&'time'&>"
38048 .cindex "frozen messages" "spool data"
38049 The message is frozen, and the freezing happened at <&'time'&>.
38051 .vitem "&%-helo_name%&&~<&'text'&>"
38052 This records the host name as specified by a remote host in a HELO or EHLO
38055 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
38056 This records the IP address of the host from which the message was received and
38057 the remote port number that was used. It is omitted for locally generated
38060 .vitem "&%-host_auth%&&~<&'text'&>"
38061 If the message was received on an authenticated SMTP connection, this records
38062 the name of the authenticator &-- the value of the
38063 &$sender_host_authenticated$& variable.
38065 .vitem &%-host_lookup_failed%&
38066 This is present if an attempt to look up the sending host's name from its IP
38067 address failed. It corresponds to the &$host_lookup_failed$& variable.
38069 .vitem "&%-host_name%&&~<&'text'&>"
38070 .cindex "reverse DNS lookup"
38071 .cindex "DNS" "reverse lookup"
38072 This records the name of the remote host from which the message was received,
38073 if the host name was looked up from the IP address when the message was being
38074 received. It is not present if no reverse lookup was done.
38076 .vitem "&%-ident%&&~<&'text'&>"
38077 For locally submitted messages, this records the login of the originating user,
38078 unless it was a trusted user and the &%-oMt%& option was used to specify an
38079 ident value. For messages received over TCP/IP, this records the ident string
38080 supplied by the remote host, if any.
38082 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
38083 This records the IP address of the local interface and the port number through
38084 which a message was received from a remote host. It is omitted for locally
38085 generated messages.
38088 The message is from a local sender.
38090 .vitem &%-localerror%&
38091 The message is a locally-generated bounce message.
38093 .vitem "&%-local_scan%&&~<&'string'&>"
38094 This records the data string that was returned by the &[local_scan()]& function
38095 when the message was received &-- the value of the &$local_scan_data$&
38096 variable. It is omitted if no data was returned.
38098 .vitem &%-manual_thaw%&
38099 The message was frozen but has been thawed manually, that is, by an explicit
38100 Exim command rather than via the auto-thaw process.
38103 A testing delivery process was started using the &%-N%& option to suppress any
38104 actual deliveries, but delivery was deferred. At any further delivery attempts,
38107 .vitem &%-received_protocol%&
38108 This records the value of the &$received_protocol$& variable, which contains
38109 the name of the protocol by which the message was received.
38111 .vitem &%-sender_set_untrusted%&
38112 The envelope sender of this message was set by an untrusted local caller (used
38113 to ensure that the caller is displayed in queue listings).
38115 .vitem "&%-spam_score_int%&&~<&'number'&>"
38116 If a message was scanned by SpamAssassin, this is present. It records the value
38117 of &$spam_score_int$&.
38119 .vitem &%-tls_certificate_verified%&
38120 A TLS certificate was received from the client that sent this message, and the
38121 certificate was verified by the server.
38123 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
38124 When the message was received over an encrypted connection, this records the
38125 name of the cipher suite that was used.
38127 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
38128 When the message was received over an encrypted connection, and a certificate
38129 was received from the client, this records the Distinguished Name from that
38133 Following the options there is a list of those addresses to which the message
38134 is not to be delivered. This set of addresses is initialized from the command
38135 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
38136 is set; otherwise it starts out empty. Whenever a successful delivery is made,
38137 the address is added to this set. The addresses are kept internally as a
38138 balanced binary tree, and it is a representation of that tree which is written
38139 to the spool file. If an address is expanded via an alias or forward file, the
38140 original address is added to the tree when deliveries to all its child
38141 addresses are complete.
38143 If the tree is empty, there is a single line in the spool file containing just
38144 the text &"XX"&. Otherwise, each line consists of two letters, which are either
38145 Y or N, followed by an address. The address is the value for the node of the
38146 tree, and the letters indicate whether the node has a left branch and/or a
38147 right branch attached to it, respectively. If branches exist, they immediately
38148 follow. Here is an example of a three-node tree:
38150 YY darcy@austen.fict.example
38151 NN alice@wonderland.fict.example
38152 NN editor@thesaurus.ref.example
38154 After the non-recipients tree, there is a list of the message's recipients.
38155 This is a simple list, preceded by a count. It includes all the original
38156 recipients of the message, including those to whom the message has already been
38157 delivered. In the simplest case, the list contains one address per line. For
38161 editor@thesaurus.ref.example
38162 darcy@austen.fict.example
38164 alice@wonderland.fict.example
38166 However, when a child address has been added to the top-level addresses as a
38167 result of the use of the &%one_time%& option on a &(redirect)& router, each
38168 line is of the following form:
38170 <&'top-level address'&> <&'errors_to address'&> &&&
38171 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
38173 The 01 flag bit indicates the presence of the three other fields that follow
38174 the top-level address. Other bits may be used in future to support additional
38175 fields. The <&'parent number'&> is the offset in the recipients list of the
38176 original parent of the &"one time"& address. The first two fields are the
38177 envelope sender that is associated with this address and its length. If the
38178 length is zero, there is no special envelope sender (there are then two space
38179 characters in the line). A non-empty field can arise from a &(redirect)& router
38180 that has an &%errors_to%& setting.
38183 A blank line separates the envelope and status information from the headers
38184 which follow. A header may occupy several lines of the file, and to save effort
38185 when reading it in, each header is preceded by a number and an identifying
38186 character. The number is the number of characters in the header, including any
38187 embedded newlines and the terminating newline. The character is one of the
38191 .row <&'blank'&> "header in which Exim has no special interest"
38192 .row &`B`& "&'Bcc:'& header"
38193 .row &`C`& "&'Cc:'& header"
38194 .row &`F`& "&'From:'& header"
38195 .row &`I`& "&'Message-id:'& header"
38196 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
38197 .row &`R`& "&'Reply-To:'& header"
38198 .row &`S`& "&'Sender:'& header"
38199 .row &`T`& "&'To:'& header"
38200 .row &`*`& "replaced or deleted header"
38203 Deleted or replaced (rewritten) headers remain in the spool file for debugging
38204 purposes. They are not transmitted when the message is delivered. Here is a
38205 typical set of headers:
38207 111P Received: by hobbit.fict.example with local (Exim 4.00)
38208 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
38209 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
38210 038* X-rewrote-sender: bb@hobbit.fict.example
38211 042* From: Bilbo Baggins <bb@hobbit.fict.example>
38212 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
38213 099* To: alice@wonderland.fict.example, rdo@foundation,
38214 darcy@austen.fict.example, editor@thesaurus.ref.example
38215 104T To: alice@wonderland.fict.example, rdo@foundation.example,
38216 darcy@austen.fict.example, editor@thesaurus.ref.example
38217 038 Date: Fri, 11 May 2001 10:28:59 +0100
38219 The asterisked headers indicate that the envelope sender, &'From:'& header, and
38220 &'To:'& header have been rewritten, the last one because routing expanded the
38221 unqualified domain &'foundation'&.
38222 .ecindex IIDforspo1
38223 .ecindex IIDforspo2
38224 .ecindex IIDforspo3
38226 . ////////////////////////////////////////////////////////////////////////////
38227 . ////////////////////////////////////////////////////////////////////////////
38229 .chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&&
38233 DKIM is a mechanism by which messages sent by some entity can be provably
38234 linked to a domain which that entity controls. It permits reputation to
38235 be tracked on a per-domain basis, rather than merely upon source IP address.
38236 DKIM is documented in RFC 4871.
38238 DKIM support is compiled into Exim by default if TLS support is present.
38239 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
38241 Exim's DKIM implementation allows for
38243 Signing outgoing messages: This function is implemented in the SMTP transport.
38244 It can co-exist with all other Exim features
38245 (including transport filters)
38246 except cutthrough delivery.
38248 Verifying signatures in incoming messages: This is implemented by an additional
38249 ACL (acl_smtp_dkim), which can be called several times per message, with
38250 different signature contexts.
38253 In typical Exim style, the verification implementation does not include any
38254 default "policy". Instead it enables you to build your own policy using
38255 Exim's standard controls.
38257 Please note that verification of DKIM signatures in incoming mail is turned
38258 on by default for logging purposes. For each signature in incoming email,
38259 exim will log a line displaying the most important signature details, and the
38260 signature status. Here is an example (with line-breaks added for clarity):
38262 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
38263 d=facebookmail.com s=q1-2009b
38264 c=relaxed/relaxed a=rsa-sha1
38265 i=@facebookmail.com t=1252484542 [verification succeeded]
38267 You might want to turn off DKIM verification processing entirely for internal
38268 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
38269 control modifier. This should typically be done in the RCPT ACL, at points
38270 where you accept mail from relay sources (internal hosts or authenticated
38274 .section "Signing outgoing messages" "SECDKIMSIGN"
38275 .cindex "DKIM" "signing"
38277 Signing is enabled by setting private options on the SMTP transport.
38278 These options take (expandable) strings as arguments.
38280 .option dkim_domain smtp string&!! unset
38282 The domain you want to sign with. The result of this expanded
38283 option is put into the &%$dkim_domain%& expansion variable.
38284 If it is empty after expansion, DKIM signing is not done.
38286 .option dkim_selector smtp string&!! unset
38288 This sets the key selector string. You can use the &%$dkim_domain%& expansion
38289 variable to look up a matching selector. The result is put in the expansion
38290 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
38291 option along with &%$dkim_domain%&.
38293 .option dkim_private_key smtp string&!! unset
38295 This sets the private key to use. You can use the &%$dkim_domain%& and
38296 &%$dkim_selector%& expansion variables to determine the private key to use.
38297 The result can either
38299 be a valid RSA private key in ASCII armor, including line breaks.
38301 start with a slash, in which case it is treated as a file that contains
38304 be "0", "false" or the empty string, in which case the message will not
38305 be signed. This case will not result in an error, even if &%dkim_strict%&
38309 .option dkim_canon smtp string&!! unset
38311 This option sets the canonicalization method used when signing a message.
38312 The DKIM RFC currently supports two methods: "simple" and "relaxed".
38313 The option defaults to "relaxed" when unset. Note: the current implementation
38314 only supports using the same canonicalization method for both headers and body.
38316 .option dkim_strict smtp string&!! unset
38318 This option defines how Exim behaves when signing a message that
38319 should be signed fails for some reason. When the expansion evaluates to
38320 either "1" or "true", Exim will defer. Otherwise Exim will send the message
38321 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
38324 .option dkim_sign_headers smtp string&!! unset
38326 When set, this option must expand to (or be specified as) a colon-separated
38327 list of header names. Headers with these names will be included in the message
38328 signature. When unspecified, the header names recommended in RFC4871 will be
38332 .section "Verifying DKIM signatures in incoming mail" "SECID514"
38333 .cindex "DKIM" "verification"
38335 Verification of DKIM signatures in SMTP incoming email is implemented via the
38336 &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each
38337 syntactically(!) correct signature in the incoming message.
38338 A missing ACL definition defaults to accept.
38339 If any ACL call does not accept, the message is not accepted.
38340 If a cutthrough delivery was in progress for the message it is
38341 summarily dropped (having wasted the transmission effort).
38343 To evaluate the signature in the ACL a large number of expansion variables
38344 containing the signature status and its details are set up during the
38345 runtime of the ACL.
38347 Calling the ACL only for existing signatures is not sufficient to build
38348 more advanced policies. For that reason, the global option
38349 &%dkim_verify_signers%&, and a global expansion variable
38350 &%$dkim_signers%& exist.
38352 The global option &%dkim_verify_signers%& can be set to a colon-separated
38353 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
38354 called. It is expanded when the message has been received. At this point,
38355 the expansion variable &%$dkim_signers%& already contains a colon-separated
38356 list of signer domains and identities for the message. When
38357 &%dkim_verify_signers%& is not specified in the main configuration,
38360 dkim_verify_signers = $dkim_signers
38362 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
38363 DKIM signature in the message. Current DKIM verifiers may want to explicitly
38364 call the ACL for known domains or identities. This would be achieved as follows:
38366 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
38368 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
38369 and "ebay.com", plus all domains and identities that have signatures in the message.
38370 You can also be more creative in constructing your policy. For example:
38372 dkim_verify_signers = $sender_address_domain:$dkim_signers
38375 If a domain or identity is listed several times in the (expanded) value of
38376 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
38379 Inside the &%acl_smtp_dkim%&, the following expansion variables are
38380 available (from most to least important):
38384 .vitem &%$dkim_cur_signer%&
38385 The signer that is being evaluated in this ACL run. This can be a domain or
38386 an identity. This is one of the list items from the expanded main option
38387 &%dkim_verify_signers%& (see above).
38389 .vitem &%$dkim_verify_status%&
38390 A string describing the general status of the signature. One of
38392 &%none%&: There is no signature in the message for the current domain or
38393 identity (as reflected by &%$dkim_cur_signer%&).
38395 &%invalid%&: The signature could not be verified due to a processing error.
38396 More detail is available in &%$dkim_verify_reason%&.
38398 &%fail%&: Verification of the signature failed. More detail is
38399 available in &%$dkim_verify_reason%&.
38401 &%pass%&: The signature passed verification. It is valid.
38404 .vitem &%$dkim_verify_reason%&
38405 A string giving a little bit more detail when &%$dkim_verify_status%& is either
38406 "fail" or "invalid". One of
38408 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
38409 key for the domain could not be retrieved. This may be a temporary problem.
38411 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
38412 record for the domain is syntactically invalid.
38414 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
38415 body hash does not match the one specified in the signature header. This
38416 means that the message body was modified in transit.
38418 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
38419 could not be verified. This may mean that headers were modified,
38420 re-written or otherwise changed in a way which is incompatible with
38421 DKIM verification. It may of course also mean that the signature is forged.
38424 .vitem &%$dkim_domain%&
38425 The signing domain. IMPORTANT: This variable is only populated if there is
38426 an actual signature in the message for the current domain or identity (as
38427 reflected by &%$dkim_cur_signer%&).
38429 .vitem &%$dkim_identity%&
38430 The signing identity, if present. IMPORTANT: This variable is only populated
38431 if there is an actual signature in the message for the current domain or
38432 identity (as reflected by &%$dkim_cur_signer%&).
38434 .vitem &%$dkim_selector%&
38435 The key record selector string.
38437 .vitem &%$dkim_algo%&
38438 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
38440 .vitem &%$dkim_canon_body%&
38441 The body canonicalization method. One of 'relaxed' or 'simple'.
38443 .vitem &%dkim_canon_headers%&
38444 The header canonicalization method. One of 'relaxed' or 'simple'.
38446 .vitem &%$dkim_copiedheaders%&
38447 A transcript of headers and their values which are included in the signature
38448 (copied from the 'z=' tag of the signature).
38449 Note that RFC6376 requires that verification fail if the From: header is
38450 not included in the signature. Exim does not enforce this; sites wishing
38451 strict enforcement should code the check explicitly.
38453 .vitem &%$dkim_bodylength%&
38454 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
38455 limit was set by the signer, "9999999999999" is returned. This makes sure
38456 that this variable always expands to an integer value.
38458 .vitem &%$dkim_created%&
38459 UNIX timestamp reflecting the date and time when the signature was created.
38460 When this was not specified by the signer, "0" is returned.
38462 .vitem &%$dkim_expires%&
38463 UNIX timestamp reflecting the date and time when the signer wants the
38464 signature to be treated as "expired". When this was not specified by the
38465 signer, "9999999999999" is returned. This makes it possible to do useful
38466 integer size comparisons against this value.
38468 .vitem &%$dkim_headernames%&
38469 A colon-separated list of names of headers included in the signature.
38471 .vitem &%$dkim_key_testing%&
38472 "1" if the key record has the "testing" flag set, "0" if not.
38474 .vitem &%$dkim_key_nosubdomains%&
38475 "1" if the key record forbids subdomaining, "0" otherwise.
38477 .vitem &%$dkim_key_srvtype%&
38478 Service type (tag s=) from the key record. Defaults to "*" if not specified
38481 .vitem &%$dkim_key_granularity%&
38482 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
38485 .vitem &%$dkim_key_notes%&
38486 Notes from the key record (tag n=).
38488 .vitem &%$dkim_key_length%&
38489 Number of bits in the key.
38492 In addition, two ACL conditions are provided:
38495 .vitem &%dkim_signers%&
38496 ACL condition that checks a colon-separated list of domains or identities
38497 for a match against the domain or identity that the ACL is currently verifying
38498 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
38499 verb to a group of domains or identities. For example:
38502 # Warn when Mail purportedly from GMail has no gmail signature
38503 warn log_message = GMail sender without gmail.com DKIM signature
38504 sender_domains = gmail.com
38505 dkim_signers = gmail.com
38509 Note that the above does not check for a total lack of DKIM signing;
38510 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
38512 .vitem &%dkim_status%&
38513 ACL condition that checks a colon-separated list of possible DKIM verification
38514 results against the actual result of verification. This is typically used
38515 to restrict an ACL verb to a list of verification outcomes, for example:
38518 deny message = Mail from Paypal with invalid/missing signature
38519 sender_domains = paypal.com:paypal.de
38520 dkim_signers = paypal.com:paypal.de
38521 dkim_status = none:invalid:fail
38524 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
38525 see the documentation of the &%$dkim_verify_status%& expansion variable above
38526 for more information of what they mean.
38529 . ////////////////////////////////////////////////////////////////////////////
38530 . ////////////////////////////////////////////////////////////////////////////
38532 .chapter "Proxies" "CHAPproxies" &&&
38534 .cindex "proxy support"
38535 .cindex "proxy" "access via"
38537 A proxy is an intermediate system through which communication is passed.
38538 Proxies may provide a security, availability or load-distribution function.
38541 .section "Inbound proxies" SECTproxyInbound
38542 .cindex proxy inbound
38543 .cindex proxy "server side"
38544 .cindex proxy "Proxy protocol"
38545 .cindex "Proxy protocol" proxy
38547 Exim has support for receiving inbound SMTP connections via a proxy
38548 that uses &"Proxy Protocol"& to speak to it.
38549 To include this support, include &"SUPPORT_PROXY=yes"&
38552 It was built on specifications from:
38553 (&url(http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt)).
38554 That URL was revised in May 2014 to version 2 spec:
38555 (&url(http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e)).
38557 The purpose of this facility is so that an application load balancer,
38558 such as HAProxy, can sit in front of several Exim servers
38559 to distribute load.
38560 Exim uses the local protocol communication with the proxy to obtain
38561 the remote SMTP system IP address and port information.
38562 There is no logging if a host passes or
38563 fails Proxy Protocol negotiation, but it can easily be determined and
38564 recorded in an ACL (example is below).
38566 Use of a proxy is enabled by setting the &%hosts_proxy%&
38567 main configuration option to a hostlist; connections from these
38568 hosts will use Proxy Protocol.
38569 Exim supports both version 1 and version 2 of the Proxy Protocol and
38570 automatically determines which version is in use.
38572 The Proxy Protocol header is the first data received on a TCP connection
38573 and is inserted before any TLS-on-connect handshake from the client; Exim
38574 negotiates TLS between Exim-as-server and the remote client, not between
38575 Exim and the proxy server.
38577 The following expansion variables are usable
38578 (&"internal"& and &"external"& here refer to the interfaces
38581 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
38582 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
38583 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
38584 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
38585 &'proxy_session '& boolean: SMTP connection via proxy
38587 If &$proxy_session$& is set but &$proxy_external_address$& is empty
38588 there was a protocol error.
38590 Since the real connections are all coming from the proxy, and the
38591 per host connection tracking is done before Proxy Protocol is
38592 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
38593 handle all of the parallel volume you expect per inbound proxy.
38594 With the option set so high, you lose the ability
38595 to protect your server from many connections from one IP.
38596 In order to prevent your server from overload, you
38597 need to add a per connection ratelimit to your connect ACL.
38598 A possible solution is:
38600 # Set max number of connections per host
38602 # Or do some kind of IP lookup in a flat file or database
38603 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
38605 defer message = Too many connections from this IP right now
38606 ratelimit = LIMIT / 5s / per_conn / strict
38611 .section "Outbound proxies" SECTproxySOCKS
38612 .cindex proxy outbound
38613 .cindex proxy "client side"
38614 .cindex proxy SOCKS
38615 .cindex SOCKS proxy
38616 Exim has support for sending outbound SMTP via a proxy
38617 using a protocol called SOCKS5 (defined by RFC1928).
38618 The support can be optionally included by defining SUPPORT_SOCKS=yes in
38621 Use of a proxy is enabled by setting the &%socks_proxy%& option
38622 on an smtp transport.
38623 The option value is expanded and should then be a list
38624 (colon-separated by default) of proxy specifiers.
38625 Each proxy specifier is a list
38626 (space-separated by default) where the initial element
38627 is an IP address and any subsequent elements are options.
38629 Options are a string <name>=<value>.
38630 The list of options is in the following table:
38632 &'auth '& authentication method
38633 &'name '& authentication username
38634 &'pass '& authentication password
38636 &'tmo '& connection timeout
38638 &'weight '& selection bias
38641 More details on each of these options follows:
38644 .cindex authentication "to proxy"
38645 .cindex proxy authentication
38646 &%auth%&: Either &"none"& (default) or &"name"&.
38647 Using &"name"& selects username/password authentication per RFC 1929
38648 for access to the proxy.
38649 Default is &"none"&.
38651 &%name%&: sets the username for the &"name"& authentication method.
38654 &%pass%&: sets the password for the &"name"& authentication method.
38657 &%port%&: the TCP port number to use for the connection to the proxy.
38660 &%tmo%&: sets a connection timeout in seconds for this proxy.
38663 &%pri%&: specifies a priority for the proxy within the list,
38664 higher values being tried first.
38665 The default priority is 1.
38667 &%weight%&: specifies a selection bias.
38668 Within a priority set servers are queried in a random fashion,
38669 weighted by this value.
38670 The default value for selection bias is 1.
38673 Proxies from the list are tried according to their priority
38674 and weight settings until one responds. The timeout for the
38675 overall connection applies to the set of proxied attempts.
38677 .section Logging SECTproxyLog
38678 To log the (local) IP of a proxy in the incoming or delivery logline,
38679 add &"+proxy"& to the &%log_selector%& option.
38680 This will add a component tagged with &"PRX="& to the line.
38682 . ////////////////////////////////////////////////////////////////////////////
38683 . ////////////////////////////////////////////////////////////////////////////
38685 .chapter "Internationalisation" "CHAPi18n" &&&
38686 "Internationalisation""
38687 .cindex internationalisation "email address"
38690 .cindex UTF-8 "mail name handling"
38692 Exim has support for Internationalised mail names.
38693 To include this it must be built with SUPPORT_I18N and the libidn library.
38694 Standards supported are RFCs 2060, 5890, 6530 and 6533.
38696 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
38697 instead of it) then IDNA2008 is supported; this adds an extra library
38698 requirement, upon libidn2.
38700 .section "MTA operations" SECTi18nMTA
38701 .cindex SMTPUTF8 "ESMTP option"
38702 The main configuration option &%smtputf8_advertise_hosts%& specifies
38703 a host list. If this matches the sending host and
38704 accept_8bitmime is true (the default) then the ESMTP option
38705 SMTPUTF8 will be advertised.
38707 If the sender specifies the SMTPUTF8 option on a MAIL command
38708 international handling for the message is enabled and
38709 the expansion variable &$message_smtputf8$& will have value TRUE.
38711 The option &%allow_utf8_domains%& is set to true for this
38712 message. All DNS lookups are converted to a-label form
38713 whatever the setting of &%allow_utf8_domains%&
38714 when Exim is built with SUPPORT_I18N.
38716 Both localparts and domain are maintained as the original
38717 UTF-8 form internally; any comparison or regular-expression use will
38718 require appropriate care. Filenames created, eg. by
38719 the appendfile transport, will have UTF-8 names.
38721 HELO names sent by the smtp transport will have any UTF-8
38722 components expanded to a-label form,
38723 and any certificate name checks will be done using the a-label
38726 .cindex log protocol
38727 .cindex SMTPUTF8 logging
38728 Log lines and Received-by: header lines will acquire a "utf8"
38729 prefix on the protocol element, eg. utf8esmtp.
38731 The following expansion operators can be used:
38733 ${utf8_domain_to_alabel:str}
38734 ${utf8_domain_from_alabel:str}
38735 ${utf8_localpart_to_alabel:str}
38736 ${utf8_localpart_from_alabel:str}
38739 ACLs may use the following modifier:
38741 control = utf8_downconvert
38742 control = utf8_downconvert/<value>
38744 This sets a flag requiring that addresses are converted to
38745 a-label form before smtp delivery, for use in a
38746 Message Submission Agent context.
38747 If a value is appended it may be:
38749 &`1 `& (default) mandatory downconversion
38750 &`0 `& no downconversion
38751 &`-1 `& if SMTPUTF8 not supported by destination host
38754 If mua_wrapper is set, the utf8_downconvert control
38755 is initially set to -1.
38758 There is no explicit support for VRFY and EXPN.
38759 Configurations supporting these should inspect
38760 &$smtp_command_argument$& for an SMTPUTF8 argument.
38762 There is no support for LMTP on Unix sockets.
38763 Using the "lmtp" protocol option on an smtp transport,
38764 for LMTP over TCP, should work as expected.
38766 There is no support for DSN unitext handling,
38767 and no provision for converting logging from or to UTF-8.
38771 .section "MDA operations" SECTi18nMDA
38772 To aid in constructing names suitable for IMAP folders
38773 the following expansion operator can be used:
38775 ${imapfolder {<string>} {<sep>} {<specials>}}
38778 The string is converted from the charset specified by
38779 the "headers charset" command (in a filter file)
38780 or &%headers_charset%& main configuration option (otherwise),
38782 modified UTF-7 encoding specified by RFC 2060,
38783 with the following exception: All occurences of <sep>
38784 (which has to be a single character)
38785 are replaced with periods ("."), and all periods and slashes that are not
38786 <sep> and are not in the <specials> string are BASE64 encoded.
38788 The third argument can be omitted, defaulting to an empty string.
38789 The second argument can be omitted, defaulting to "/".
38791 This is the encoding used by Courier for Maildir names on disk, and followed
38792 by many other IMAP servers.
38796 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
38797 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
38798 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
38801 Note that the source charset setting is vital, and also that characters
38802 must be representable in UTF-16.
38805 . ////////////////////////////////////////////////////////////////////////////
38806 . ////////////////////////////////////////////////////////////////////////////
38808 .chapter "Events" "CHAPevents" &&&
38812 The events mechanism in Exim can be used to intercept processing at a number
38813 of points. It was originally invented to give a way to do customised logging
38814 actions (for example, to a database) but can also be used to modify some
38815 processing actions.
38817 Most installations will never need to use Events.
38818 The support can be left out of a build by defining DISABLE_EVENT=yes
38819 in &_Local/Makefile_&.
38821 There are two major classes of events: main and transport.
38822 The main configuration option &%event_action%& controls reception events;
38823 a transport option &%event_action%& controls delivery events.
38825 Both options are a string which is expanded when the event fires.
38826 An example might look like:
38827 .cindex logging custom
38829 event_action = ${if eq {msg:delivery}{$event_name} \
38830 {${lookup pgsql {SELECT * FROM record_Delivery( \
38831 '${quote_pgsql:$sender_address_domain}',\
38832 '${quote_pgsql:${lc:$sender_address_local_part}}', \
38833 '${quote_pgsql:$domain}', \
38834 '${quote_pgsql:${lc:$local_part}}', \
38835 '${quote_pgsql:$host_address}', \
38836 '${quote_pgsql:${lc:$host}}', \
38837 '${quote_pgsql:$message_exim_id}')}} \
38841 Events have names which correspond to the point in process at which they fire.
38842 The name is placed in the variable &$event_name$& and the event action
38843 expansion must check this, as it will be called for every possible event type.
38845 The current list of events is:
38847 &`msg:complete after main `& per message
38848 &`msg:delivery after transport `& per recipient
38849 &`msg:rcpt:host:defer after transport `& per recipient per host
38850 &`msg:rcpt:defer after transport `& per recipient
38851 &`msg:host:defer after transport `& per attempt
38852 &`msg:fail:delivery after main `& per recipient
38853 &`msg:fail:internal after main `& per recipient
38854 &`tcp:connect before transport `& per connection
38855 &`tcp:close after transport `& per connection
38856 &`tls:cert before both `& per certificate in verification chain
38857 &`smtp:connect after transport `& per connection
38859 New event types may be added in future.
38861 The event name is a colon-separated list, defining the type of
38862 event in a tree of possibilities. It may be used as a list
38863 or just matched on as a whole. There will be no spaces in the name.
38865 The second column in the table above describes whether the event fires
38866 before or after the action is associates with. Those which fire before
38867 can be used to affect that action (more on this below).
38869 An additional variable, &$event_data$&, is filled with information varying
38870 with the event type:
38872 &`msg:delivery `& smtp confirmation message
38873 &`msg:rcpt:host:defer `& error string
38874 &`msg:rcpt:defer `& error string
38875 &`msg:host:defer `& error string
38876 &`tls:cert `& verification chain depth
38877 &`smtp:connect `& smtp banner
38880 The :defer events populate one extra variable: &$event_defer_errno$&.
38882 For complex operations an ACL expansion can be used in &%event_action%&
38883 however due to the multiple contexts that Exim operates in during
38884 the course of its processing:
38886 variables set in transport events will not be visible outside that
38889 acl_m variables in a server context are lost on a new connection,
38890 and after smtp helo/ehlo/mail/starttls/rset commands
38892 Using an ACL expansion with the logwrite modifier can be
38893 a useful way of writing to the main log.
38895 The expansion of the event_action option should normally
38896 return an empty string. Should it return anything else the
38897 following will be forced:
38899 &`msg:delivery `& (ignored)
38900 &`msg:host:defer `& (ignored)
38901 &`msg:fail:delivery`& (ignored)
38902 &`tcp:connect `& do not connect
38903 &`tcp:close `& (ignored)
38904 &`tls:cert `& refuse verification
38905 &`smtp:connect `& close connection
38907 No other use is made of the result string.
38909 For a tcp:connect event, if the connection is being made to a proxy
38910 then the address and port variables will be that of the proxy and not
38913 For tls:cert events, if GnuTLS is in use this will trigger only per
38914 chain element received on the connection.
38915 For OpenSSL it will trigger for every chain element including those
38918 . ////////////////////////////////////////////////////////////////////////////
38919 . ////////////////////////////////////////////////////////////////////////////
38921 .chapter "Adding new drivers or lookup types" "CHID13" &&&
38922 "Adding drivers or lookups"
38923 .cindex "adding drivers"
38924 .cindex "new drivers, adding"
38925 .cindex "drivers" "adding new"
38926 The following actions have to be taken in order to add a new router, transport,
38927 authenticator, or lookup type to Exim:
38930 Choose a name for the driver or lookup type that does not conflict with any
38931 existing name; I will use &"newdriver"& in what follows.
38933 Add to &_src/EDITME_& the line:
38935 <&'type'&>&`_NEWDRIVER=yes`&
38937 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
38938 code is not to be included in the binary by default, comment this line out. You
38939 should also add any relevant comments about the driver or lookup type.
38941 Add to &_src/config.h.defaults_& the line:
38943 #define <type>_NEWDRIVER
38946 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
38947 and create a table entry as is done for all the other drivers and lookup types.
38949 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
38950 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
38951 Add your &`NEWDRIVER`& to that list.
38952 As long as the dynamic module would be named &_newdriver.so_&, you can use the
38953 simple form that most lookups have.
38955 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
38956 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
38957 driver or lookup type and add it to the definition of OBJ.
38959 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
38962 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
38963 as for other drivers and lookups.
38966 Then all you need to do is write the code! A good way to start is to make a
38967 proforma by copying an existing module of the same type, globally changing all
38968 occurrences of the name, and cutting out most of the code. Note that any
38969 options you create must be listed in alphabetical order, because the tables are
38970 searched using a binary chop procedure.
38972 There is a &_README_& file in each of the sub-directories of &_src_& describing
38973 the interface that is expected.
38978 . ////////////////////////////////////////////////////////////////////////////
38979 . ////////////////////////////////////////////////////////////////////////////
38981 . /////////////////////////////////////////////////////////////////////////////
38982 . These lines are processing instructions for the Simple DocBook Processor that
38983 . Philip Hazel has developed as a less cumbersome way of making PostScript and
38984 . PDFs than using xmlto and fop. They will be ignored by all other XML
38986 . /////////////////////////////////////////////////////////////////////////////
38991 foot_right_recto="&chaptertitle;"
38992 foot_right_verso="&chaptertitle;"
38996 .makeindex "Options index" "option"
38997 .makeindex "Variables index" "variable"
38998 .makeindex "Concept index" "concept"
39001 . /////////////////////////////////////////////////////////////////////////////
39002 . /////////////////////////////////////////////////////////////////////////////