Added those who've been helping with the Test Suite, before I forget.

[exim.git] / doc / doc-docbook / spec.ascd

////////////////////////////////////////////////////////////////////////////
$Cambridge: exim/doc/doc-docbook/spec.ascd,v 1.1 2005/06/16 10:32:31 ph10 Exp $

This is the primary source of the Exim Manual. It is an AsciiDoc document
that is converted into DocBook XML for subsequent conversion into printing
and online formats. The markup used herein is traditional AsciiDoc markup,
with some extras. The markup is summarized in a file called AdMarkup.txt. A
private AsciiDoc configuration file specifies how the extra markup is to be
translated into DocBook XML. You MUST use this private AsciiDoc markup if you
want to get sensible results from processing this document.
////////////////////////////////////////////////////////////////////////////



////////////////////////////////////////////////////////////////////////////
I am abusing the <abstract> DocBook element as the only trivial way of getting
this information onto the title verso page in the printed renditions. A better
title page would be a useful improvement. The <abstract> element is removed by
preprocessing for the HTML renditions, and the whole <docbookinfo> element is
removed for ascii output formats.
////////////////////////////////////////////////////////////////////////////

Specification of the Exim Mail Transfer Agent
=============================================
:abstract:        University of Cambridge Computing Service, New Museums Site, Pembroke Street, Cambridge CB2 3QH, England
:author:          Philip Hazel
:copyright:       University of Cambridge
:cpyear:          2005
:date:            13 May 2005
:doctitleabbrev:  The Exim MTA
:revision:        4.50


//////////////////////////////////////////////////////////////////////////////
***WARNING*** Do not put anything, not even a titleabbrev, setting before
the first chapter (luckily it does not need one) because if you do, AsciiDoc
creates an empty <preface> element, which we do not want.
//////////////////////////////////////////////////////////////////////////////

Introduction
------------

////////////////////////////////////////////////////////////////////////////
These are definitions of AsciiDoc "attributes" that are in effect "variables"
whose values can be substituted. The first makes index entries shorter. The
second avoids problems with literal asterisks getting tangled up with bold
emphasis quotes. The others are here for convenience of editing.

***WARNING*** The positioning of these definitions, after the first Chapter
title, seems to be important. If they are placed earlier, they give rise to
incorrect XML.
////////////////////////////////////////////////////////////////////////////

:ACL:             access control lists (ACLs)
:star:            *
:previousversion: 4.40
:version:         4.50


////////////////////////////////////////////////////////////////////////////
This chunk of literal XML implements index entries of the form "x, see y" and
"x, see also y". It didn't seem worth inventing AsciiDoc markup for this,
because is it not something that is likely to change often.
////////////////////////////////////////////////////////////////////////////

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
<indexterm role="concept">
  <primary>$1, $2, etc.</primary>
  <see><emphasis>numerical variables</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>address</primary>
  <secondary>rewriting</secondary>
  <see><emphasis>rewriting</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>CR character</primary>
  <see><emphasis>carriage return</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>CRL</primary>
  <see><emphasis>certificate revocation list</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>delivery</primary>
  <secondary>failure report</secondary>
  <see><emphasis>bounce message</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>dialup</primary>
  <see><emphasis>intermittently connected hosts</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>exiscan</primary>
  <see><emphasis>content scanning</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>failover</primary>
  <see><emphasis>fallback</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>fallover</primary>
  <see><emphasis>fallback</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>filter</primary>
  <secondary>Sieve</secondary>
  <see><emphasis>Sieve filter</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>ident</primary>
  <see><emphasis>RFC 1413</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>LF character</primary>
  <see><emphasis>linefeed</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>maximum</primary>
  <see><emphasis>limit</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>no_<emphasis>xxx</emphasis></primary>
  <see>entry for xxx</see>
</indexterm>
<indexterm role="concept">
  <primary>NUL</primary>
  <see><emphasis>binary zero</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>passwd file</primary>
  <see><emphasis>/etc/passwd</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>process id</primary>
  <see><emphasis>pid</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>RBL</primary>
  <see><emphasis>DNS list</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>redirection</primary>
  <see><emphasis>address redirection</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>return path</primary>
  <seealso><emphasis>envelope sender</emphasis></seealso>
</indexterm>
<indexterm role="concept">
  <primary>scanning</primary>
  <see><emphasis>content scanning</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>SSL</primary>
  <see><emphasis>TLS</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>string</primary>
  <secondary>expansion</secondary>
  <see><emphasis>expansion</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>top bit</primary>
  <see><emphasis>8-bit characters</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>variables</primary>
  <see><emphasis>expansion, variables</emphasis></see>
</indexterm>
<indexterm role="concept">
  <primary>zero, binary</primary>
  <see><emphasis>binary zero</emphasis></see>
</indexterm>
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++


////////////////////////////////////////////////////////////////////////////
OK, now we start with the real data for this first chapter.
////////////////////////////////////////////////////////////////////////////

Exim is a mail transfer agent (MTA) for hosts that are running Unix or
Unix-like operating systems. It was designed on the assumption that it would be
run on hosts that are permanently connected to the Internet. However, it can be
used on intermittently connected hosts with suitable configuration adjustments.

Configuration files currently exist for the following operating systems: AIX,
BSD/OS (aka BSDI), Darwin (Mac OS X), DGUX, FreeBSD, GNU/Hurd, GNU/Linux,
HI-OSF (Hitachi), HP-UX, IRIX, MIPS RISCOS, NetBSD, OpenBSD, QNX, SCO, SCO
SVR4.2 (aka UNIX-SV), Solaris (aka SunOS5), SunOS4, Tru64-Unix (formerly
Digital UNIX, formerly DEC-OSF1), Ultrix, and Unixware. Some of these operating
systems are no longer current and cannot easily be tested, so the configuration
files may no longer work in practice.

There are also configuration files for compiling Exim in the Cygwin environment
that can be installed on systems running Windows. However, this document does
not contain any information about running Exim in the Cygwin environment.

The terms and conditions for the use and distribution of Exim are contained in
the file _NOTICE_. Exim is distributed under the terms of the GNU General
Public Licence, a copy of which may be found in the file _LICENCE_.

The use, supply or promotion of Exim for the purpose of sending bulk,
unsolicited electronic mail is incompatible with the basic aims of the program,
which revolve around the free provision of a service that enhances the quality
of personal communications. The author of Exim regards indiscriminate
mass-mailing as an antisocial, irresponsible abuse of the Internet.

Exim owes a great deal to Smail 3 and its author, Ron Karr. Without the
experience of running and working on the Smail 3 code, I could never have
contemplated starting to write a new MTA. Many of the ideas and user interfaces
were originally taken from Smail 3, though the actual code of Exim is entirely
new, and has developed far beyond the initial concept.

Many people, both in Cambridge and around the world, have contributed to the
development and the testing of Exim, and to porting it to various operating
systems. I am grateful to them all. The distribution now contains a file called
_ACKNOWLEDGMENTS_, in which I have started recording the names of
contributors.



Exim documentation
~~~~~~~~~~~~~~~~~~
[revisionflag="changed"]
cindex:[documentation]
This edition of the Exim specification applies to version {version} of Exim.
Substantive changes from the {previousversion} edition are marked in some
renditions of the document; this paragraph is so marked if the rendition is
capable of showing a change indicator.

This document is very much a reference manual; it is not a tutorial. The reader
is expected to have some familiarity with the SMTP mail transfer protocol and
with general Unix system administration. Although there are some discussions
and examples in places, the information is mostly organized in a way that makes
it easy to look up, rather than in a natural order for sequential reading.
Furthermore, the manual aims to cover every aspect of Exim in detail, including
a number of rarely-used, special-purpose features that are unlikely to be of
very wide interest.

cindex:[books about Exim]
An ``easier'' discussion of Exim which provides more in-depth explanatory,
introductory, and tutorial material can be found in a book entitled
'The Exim SMTP Mail Server', published by UIT Cambridge
(*http://www.uit.co.uk/exim-book/[]*).

This book also contains a chapter that gives a general introduction to SMTP and
Internet mail. Inevitably, however, the book is unlikely to be fully up-to-date
with the latest release of Exim. (Note that the earlier book about Exim,
published by O'Reilly, covers Exim 3, and many things have changed in Exim 4.)

cindex:[_doc/NewStuff_]
cindex:[_doc/ChangeLog_]
cindex:[change log]
As the program develops, there may be features in newer versions that have not
yet made it into this document, which is updated only when the most significant
digit of the fractional part of the version number changes. Specifications of
new features that are not yet in this manual are placed in the file
_doc/NewStuff_ in the Exim distribution.

Some features may be classified as ``experimental''. These may change
incompatibly while they are developing, or even be withdrawn. For this reason,
they are not documented in this manual. Information about experimental features
can be found in the file _doc/experimental.txt_.

All changes to the program (whether new features, bug fixes, or other kinds of
change) are noted briefly in the file called _doc/ChangeLog_.

cindex:[_doc/spec.txt_]
This specification itself is available as an ASCII file in _doc/spec.txt_ so
that it can easily be searched with a text editor. Other files in the _doc_
directory are:

[frame="none"]
`--------------------`------------------------------------------
_OptionLists.txt_    list of all options in alphabetical order
_dbm.discuss.txt_    discussion about DBM libraries
_exim.8_             a man page of Exim's command line options
_experimental.txt_   documentation of experimental features
_filter.txt_         specification of the filter language
_pcrepattern.txt_    specification of PCRE regular expressions
_pcretest.txt_       specification of the PCRE testing program
_Exim3.upgrade_      upgrade notes from release 2 to release 3
_Exim4.upgrade_      upgrade notes from release 3 to release 4
----------------------------------------------------------------

The main specification and the specification of the filtering language are also
available in other formats (HTML, PostScript, PDF, and Texinfo). Section
<<SECTavail>> below tells you how to get hold of these.



FTP and web sites
~~~~~~~~~~~~~~~~~
cindex:[web site]
cindex:[FTP site]
The primary distribution site for Exim is currently the University of
Cambridge's FTP site, whose contents are described in 'Where to find the Exim
distribution' below. In addition, there is a web site and an FTP site at
%exim.org%. These are now also hosted at the University of Cambridge. The
%exim.org% site was previously hosted for a number of years by Energis Squared,
formerly Planet Online Ltd, whose support I gratefully acknowledge.

As well as Exim distribution tar files, the Exim web site contains a number of
differently formatted versions of the documentation, including the
cindex:[FAQ] FAQ in both text and HTML formats. The HTML version comes with
a keyword-in-context index. A recent addition to the online information is the
cindex:[wiki]
Exim wiki (*http://www.exim.org/eximwiki/[]*).
We hope that this will make it easier for Exim users to contribute examples,
tips, and know-how for the benefit of others.



Mailing lists
~~~~~~~~~~~~~
cindex:[mailing lists,for Exim users]
The following are the three main Exim mailing lists:

[frame="none"]
`-------------------------------`----------------------------------------
'exim-users@exim.org'           general discussion list
'exim-dev@exim.org'             discussion of bugs, enhancements, etc.
'exim-announce@exim.org'        moderated, low volume announcements list
-------------------------------------------------------------------------

You can subscribe to these lists, change your existing subscriptions, and view
or search the archives via the mailing lists link on the Exim home page. The
'exim-users' mailing list is also forwarded to
*http://www.egroups.com/list/exim-users[]*, an archiving system with searching
capabilities.


Exim training
~~~~~~~~~~~~~
cindex:[training courses]
From time to time (approximately annually at the time of writing),
lecture-based training courses are run by the author of Exim in Cambridge, UK.
Details can be found on the web site
*http://www-tus.csx.cam.ac.uk/courses/exim/[]*.


Bug reports
~~~~~~~~~~~
cindex:[bug reports]
cindex:[reporting bugs]
Reports of obvious bugs should be emailed to 'bugs@exim.org'. However, if
you are unsure whether some behaviour is a bug or not, the best thing to do is
to post a message to the 'exim-users' mailing list and have it discussed.



[[SECTavail]]
Where to find the Exim distribution
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[FTP site]
cindex:[distribution,ftp site]
The master ftp site for the Exim distribution is

&&&
*ftp://ftp.csx.cam.ac.uk/pub/software/email/exim[]*
&&&

This is mirrored by

&&&
*ftp://ftp.exim.org/pub/exim[]*
&&&

The file references that follow are relative to the _exim_ directories at these
sites. There are now quite a number of independent mirror sites around the
world. Those that I know about are listed in the file called _Mirrors_.

Within the _exim_ directory there are subdirectories called _exim3_ (for
previous Exim 3 distributions), _exim4_ (for the latest Exim 4
distributions), and _Testing_ for testing versions. In the _exim4_
subdirectory, the current release can always be found in files called

&&&
_exim-n.nn.tar.gz_
_exim-n.nn.tar.bz2_
&&&

where 'n.nn' is the highest such version number in the directory. The two
files contain identical data; the only difference is the type of compression.
The _.bz2_ file is usually a lot smaller than the _.gz_ file.

cindex:[distribution,signing details]
cindex:[distribution,public key]
cindex:[public key for signed distribution]
The distributions are currently signed with Philip Hazel's GPG key. The
corresponding public key is available from a number of keyservers, and there is
also a copy in the file _Public-Key_. The signatures for the tar bundles are
in:

&&&
_exim-n.nn.tar.gz.sig_
_exim-n.nn.tar.bz2.sig_
&&&

For each released version, the log of changes is made separately available in a
separate file in the directory _ChangeLogs_ so that it is possible to
find out what has changed without having to download the entire distribution.

cindex:[documentation,available formats]
The main distribution contains ASCII versions of this specification and other
documentation; other formats of the documents are available in separate files
inside the _exim4_ directory of the FTP site:

&&&
_exim-html-n.nn.tar.gz_
_exim-pdf-n.nn.tar.gz_
_exim-postscript-n.nn.tar.gz_
_exim-texinfo-n.nn.tar.gz_
&&&

These tar files contain only the _doc_ directory, not the complete
distribution, and are also available in _.bz2_ as well as _.gz_ forms.
cindex:[FAQ]
The FAQ is available for downloading in two different formats in these files:

&&&
_exim4/FAQ.txt.gz_
_exim4/FAQ.html.tar.gz_
&&&

The first of these is a single ASCII file that can be searched with a text
editor. The second is a directory of HTML files, normally accessed by starting
at _index.html_. The HTML version of the FAQ (which is also included in the
HTML documentation tarbundle) includes a keyword-in-context index, which is
often the most convenient way of finding your way around.


Wish list
~~~~~~~~~
cindex:[wish list]
A wish list is maintained, containing ideas for new features that have been
submitted. From time to time the file is exported to the ftp site into the file
_exim4/WishList_. Items are removed from the list if they get implemented.



Contributed material
~~~~~~~~~~~~~~~~~~~~
cindex:[contributed material]
At the ftp site, there is a directory called _Contrib_ that contains
miscellaneous files contributed to the Exim community by Exim users. There is
also a collection of contributed configuration examples in
_exim4/config.samples.tar.gz_. These samples are referenced from the FAQ.



Limitations
~~~~~~~~~~~
- cindex:[limitations of Exim]
Exim is designed for use as an Internet MTA, and therefore handles addresses
in RFC 2822 domain format only.
cindex:[bang paths,not handled by Exim]
It cannot handle UUCP ``bang paths'', though simple two-component bang paths can
be converted by a straightforward rewriting configuration. This restriction
does not prevent Exim from being interfaced to UUCP as a transport mechanism,
provided that domain addresses are used.

- cindex:[domainless addresses]
cindex:[address,without domain]
Exim insists that every address it handles has a domain attached. For incoming
local messages, domainless addresses are automatically qualified with a
configured domain value. Configuration options specify from which remote
systems unqualified addresses are acceptable. These are then qualified on
arrival.

- cindex:[transport,external]
cindex:[external transports]
The only external transport currently implemented is an SMTP transport over a
TCP/IP network (using sockets, including support for IPv6). However, a pipe
transport is available, and there are facilities for writing messages to files
and pipes, optionally in 'batched SMTP' format; these facilities can be used
to send messages to some other transport mechanism such as UUCP, provided it
can handle domain-style addresses. Batched SMTP input is also catered for.

- Exim is not designed for storing mail for dial-in hosts. When the volumes of
such mail are large, it is better to get the messages ``delivered'' into files
(that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
other means.

- Although Exim does have basic facilities for scanning incoming messages, these
are not comprehensive enough to do full virus or spam scanning. Such operations
are best carried out using additional specialized software packages. If you
compile Exim with the content-scanning extension, straightforward interfaces to
a number of common scanners are provided.





Run time configuration
~~~~~~~~~~~~~~~~~~~~~~
Exim's run time configuration is held in a single text file that is divided
into a number of sections. The entries in this file consist of keywords and
values, in the style of Smail 3 configuration files. A default configuration
file which is suitable for simple online installations is provided in the
distribution, and is described in chapter <<CHAPdefconfil>> below.



Calling interface
~~~~~~~~~~~~~~~~~
cindex:[Sendmail compatibility,command line interface]
Like many MTAs, Exim has adopted the Sendmail command line interface so that it
can be a straight replacement for _/usr/lib/sendmail_ or
_/usr/sbin/sendmail_ when sending mail, but you do not need to know anything
about Sendmail in order to run Exim. For actions other than sending messages,
Sendmail-compatible options also exist, but those that produce output (for
example, %-bp%, which lists the messages on the queue) do so in Exim's own
format. There are also some additional options that are compatible with Smail
3, and some further options that are new to Exim. Chapter <<CHAPcommandline>>
documents all Exim's command line options. This information is automatically
made into the man page that forms part of the Exim distribution.

Control of messages on the queue can be done via certain privileged command
line options. There is also an optional monitor program called 'eximon', which
displays current information in an X window, and which contains a menu
interface to Exim's command line administration options.



Terminology
~~~~~~~~~~~
cindex:[terminology definitions]
cindex:[body of message,definition of]
The 'body' of a message is the actual data that the sender wants to transmit.
It is the last part of a message, and is separated from the 'header' (see
below) by a blank line.

cindex:[bounce message,definition of]
When a message cannot be delivered, it is normally returned to the sender in a
delivery failure message or a ``non-delivery report'' (NDR). The term 'bounce'
is commonly used for this action, and the error reports are often called
'bounce messages'. This is a convenient shorthand for ``delivery failure error
report''. Such messages have an empty sender address in the message's
'envelope' (see below) to ensure that they cannot themselves give rise to
further bounce messages.

The term 'default' appears frequently in this manual. It is used to qualify a
value which is used in the absence of any setting in the configuration. It may
also qualify an action which is taken unless a configuration setting specifies
otherwise.

The term 'defer' is used when the delivery of a message to a specific
destination cannot immediately take place for some reason (a remote host may be
down, or a user's local mailbox may be full). Such deliveries are 'deferred'
until a later time.

The word 'domain' is sometimes used to mean all but the first component of a
host's name. It is 'not' used in that sense here, where it normally
refers to the part of an email address following the @ sign.

cindex:[envelope, definition of]
cindex:[sender,definition of]
A message in transit has an associated 'envelope', as well as a header and a
body. The envelope contains a sender address (to which bounce messages should
be delivered), and any number of recipient addresses. References to the
sender or the recipients of a message usually mean the addresses in the
envelope. An MTA uses these addresses for delivery, and for returning bounce
messages, not the addresses that appear in the header lines.

cindex:[message header, definition of]
cindex:[header section,definition of]
The 'header' of a message is the first part of a message's text, consisting
of a number of lines, each of which has a name such as 'From:', 'To:',
'Subject:', etc. Long header lines can be split over several text lines by
indenting the continuations. The header is separated from the body by a blank
line.

cindex:[local part,definition of]
cindex:[domain,definition of]
The term 'local part', which is taken from RFC 2822, is used to refer to that
part of an email address that precedes the @ sign. The part that follows the
@ sign is called the 'domain' or 'mail domain'.

cindex:[local delivery,definition of]
cindex:[remote delivery, definition of]
The terms 'local delivery' and 'remote delivery' are used to distinguish
delivery to a file or a pipe on the local host from delivery by SMTP over
TCP/IP to a remote host.

cindex:[return path,definition of]
'Return path' is another name that is used for the sender address in a
message's envelope.

cindex:[queue,definition of]
The term 'queue' is used to refer to the set of messages awaiting delivery,
because this term is in widespread use in the context of MTAs. However, in
Exim's case the reality is more like a pool than a queue, because there is
normally no ordering of waiting messages.

cindex:[queue runner,definition of]
The term 'queue runner' is used to describe a process that scans the queue
and attempts to deliver those messages whose retry times have come. This term
is used by other MTAs, and also relates to the command %runq%, but in Exim
the waiting messages are normally processed in an unpredictable order.

cindex:[spool directory,definition of]
The term 'spool directory' is used for a directory in which Exim keeps the
messages on its queue -- that is, those that it is in the process of
delivering. This should not be confused with the directory in which local
mailboxes are stored, which is called a ``spool directory'' by some people. In
the Exim documentation, ``spool'' is always used in the first sense.






////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////

Incorporated code
-----------------
cindex:[incorporated code]
cindex:[regular expressions,library]
cindex:[PCRE]
A number of pieces of external code are included in the Exim distribution.

- Regular expressions are supported in the main Exim program and in the Exim
monitor using the freely-distributable PCRE library, copyright (c) University
of Cambridge. The source is distributed in the directory _src/pcre_. However,
this is a cut-down version of PCRE. If you want to use the PCRE library in
other programs, you should obtain and install the full version from
*ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre[]*.

- cindex:[cdb,acknowledgement]
Support for the cdb (Constant DataBase) lookup method is provided by code
contributed by Nigel Metheringham of (at the time he contributed it) Planet
Online Ltd. which contains the following statements:
+
Copyright (c) 1998 Nigel Metheringham, Planet Online Ltd
+
This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.
+
This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
the spec and sample code for cdb can be obtained from
*http://www.pobox.com/{tl}djb/cdb.html[]*. This implementation borrows some code
from Dan Bernstein's implementation (which has no license restrictions applied
to it).
+
The implementation is completely contained within the code of Exim.
It does not link against an external cdb library.

- cindex:[SPA authentication]
cindex:[Samba project]
cindex:[Microsoft Secure Password Authentication]
Client support for Microsoft's 'Secure Password Authentication' is provided
by code contributed by Marc Prud'hommeaux. Server support was contributed by
Tom Kistner. This includes code taken from the Samba project, which is released
under the Gnu GPL.

- cindex:[Cyrus]
cindex:['pwcheck' daemon]
cindex:['pwauthd' daemon]
Support for calling the Cyrus 'pwcheck' and 'saslauthd' daemons is provided
by code taken from the Cyrus-SASL library and adapted by Alexander S.
Sabourenkov. The permission notice appears below, in accordance with the
conditions expressed therein.
+
Copyright (c) 2001 Carnegie Mellon University.  All rights reserved.
+
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
+
. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.

. The name ``Carnegie Mellon University'' must not be used to
endorse or promote products derived from this software without
prior written permission. For permission or any other legal
details, please contact
+
&&&
Office of Technology Transfer
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA  15213-3890
(412) 268-4387, fax: (412) 268-7395
tech-transfer@andrew.cmu.edu
&&&

. Redistributions of any form whatsoever must retain the following
acknowledgment:
+
'This product includes software developed by Computing Services
at Carnegie Mellon University (*http://www.cmu.edu/computing/[]*).'
+
CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

. cindex:[monitor]
cindex:[X-windows]
cindex:[Athena]
The Exim Monitor program, which is an X-Window application, includes
modified versions of the Athena StripChart and TextPop widgets.
This code is copyright by DEC and MIT, and their permission notice appears
below, in accordance with the conditions expressed therein.
+
Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
+
All Rights Reserved
+
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Digital or MIT not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.
+
DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

. Many people have contributed code fragments, some large, some small, that were
not covered by any specific licence requirements. It is assumed that the
contributors are happy to see their code incoporated into Exim under the GPL.





////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////

[titleabbrev="Receiving and delivering mail"]
How Exim receives and delivers mail
-----------------------------------


Overall philosophy
~~~~~~~~~~~~~~~~~~
cindex:[design philosophy]
Exim is designed to work efficiently on systems that are permanently connected
to the Internet and are handling a general mix of mail. In such circumstances,
most messages can be delivered immediately. Consequently, Exim does not
maintain independent queues of messages for specific domains or hosts, though
it does try to send several messages in a single SMTP connection after a host
has been down, and it also maintains per-host retry information.



Policy control
~~~~~~~~~~~~~~
cindex:[policy control,overview]
Policy controls are now an important feature of MTAs that are connected to the
Internet. Perhaps their most important job is to stop MTAs being abused as
``open relays'' by misguided individuals who send out vast amounts of unsolicited
junk, and want to disguise its source. Exim provides flexible facilities for
specifying policy controls on incoming mail:

- cindex:[{ACL},introduction]
Exim 4 (unlike previous versions of Exim) implements policy controls on
incoming mail by means of 'Access Control Lists' (ACLs). Each list is a
series of statements that may either grant or deny access. ACLs can be used at
several places in the SMTP dialogue while receiving a message from a remote
host. However, the most common places are after each RCPT command, and at
the very end of the message. The sysadmin can specify conditions for accepting
or rejecting individual recipients or the entire message, respectively, at
these two points (see chapter <<CHAPACL>>). Denial of access results in an SMTP
error code.

- An ACL is also available for locally generated, non-SMTP messages. In this
case, the only available actions are to accept or deny the entire message.

- When Exim is compiled with the content-scanning extension, facilities are
provided in the ACL mechanism for passing the message to external virus and/or
spam scanning software. The result of such a scan is passed back to the ACL,
which can then use it to decide what to do with the message.

- When a message has been received, either from a remote host or from the local
host, but before the final acknowledgement has been sent, a locally supplied C
function called 'local_scan()' can be run to inspect the message and decide
whether to accept it or not (see chapter <<CHAPlocalscan>>). If the message is
accepted, the list of recipients can be modified by the function.

- Using the 'local_scan()' mechanism is another way of calling external
scanner software. The %SA-Exim% add-on package works this way. It does not
require Exim to be compiled with the content-scanning extension.

- After a message has been accepted, a further checking mechanism is available in
the form of the 'system filter' (see chapter <<CHAPsystemfilter>>). This runs
at the start of every delivery process.



User filters
~~~~~~~~~~~~
cindex:[filter,introduction]
cindex:[Sieve filter]
In a conventional Exim configuration, users are able to run private filters by
setting up appropriate _.forward_ files in their home directories. See
chapter <<CHAPredirect>> (about the ^redirect^ router) for the configuration
needed to support this, and the separate document entitled 'Exim's interfaces
to mail filtering' for user details. Two different kinds of filtering are
available:

- Sieve filters are written in the standard filtering language that is defined
by RFC 3028.

- Exim filters are written in a syntax that is unique to Exim, but which is more
powerful than Sieve, which it pre-dates.

User filters are run as part of the routing process, described below.



[[SECTmessiden]]
Message identification
~~~~~~~~~~~~~~~~~~~~~~
cindex:[message ids, details of format]
cindex:[format,of message id]
cindex:[id of message]
cindex:[base62]
cindex:[base36]
cindex:[Darwin]
cindex:[Cygwin]
Every message handled by Exim is given a 'message id' which is sixteen
characters long. It is divided into three parts, separated by hyphens, for
example `16VDhn-0001bo-D3`. Each part is a sequence of letters and digits,
normally encoding numbers in base 62. However, in the Darwin operating
system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
(avoiding the use of lower case letters) is used instead, because the message
id is used to construct file names, and the names of files in those systems are
not case-sensitive.

cindex:[pid (process id),re-use of]
The detail of the contents of the message id have changed as Exim has evolved.
Earlier versions relied on the operating system not re-using a process id (pid)
within one second. On modern operating systems, this assumption can no longer
be made, so the algorithm had to be changed. To retain backward compatibility,
the format of the message id was retained, which is why the following rules are
somewhat eccentric:

- The first six characters of the message id are the time at which the message
started to be received, to a granularity of one second. That is, this field
contains the number of seconds since the start of the epoch (the normal Unix
way of representing the date and time of day).

- After the first hyphen, the next six characters are the id of the process that
received the message.

- There are two different possibilities for the final two characters:

. cindex:[%localhost_number%]
If %localhost_number% is not set, this value is the fractional part of the
time of reception, normally in units of 1/2000 of a second, but for systems
that must use base 36 instead of base 62 (because of case-insensitive file
systems), the units are 1/1000 of a second.

. If %localhost_number% is set, it is multiplied by 200 (100) and added to
the fractional part of the time, which in this case is in units of 1/200
(1/100) of a second.

After a message has been received, Exim waits for the clock to tick at the
appropriate resolution before proceeding, so that if another message is
received by the same process, or by another process with the same (re-used)
pid, it is guaranteed that the time will be different. In most cases, the clock
will already have ticked while the message was being received.


Receiving mail
~~~~~~~~~~~~~~
cindex:[receiving mail]
cindex:[message,reception]
The only way Exim can receive mail from a remote host is using SMTP over
TCP/IP, in which case the sender and recipient addresses are tranferred using
SMTP commands. However, from a locally running process (such as a user's MUA),
there are several possibilities:

- If the process runs Exim with the %-bm% option, the message is read
non-interactively (usually via a pipe), with the recipients taken from the
command line, or from the body of the message if %-t% is also used.

- If the process runs Exim with the %-bS% option, the message is also read
non-interactively, but in this case the recipients are listed at the start of
the message in a series of SMTP RCPT commands, terminated by a DATA
command. This is so-called ``batch SMTP'' format,
but it isn't really SMTP. The SMTP commands are just another way of passing
envelope addresses in a non-interactive submission.

- If the process runs Exim with the %-bs% option, the message is read
interactively, using the SMTP protocol. A two-way pipe is normally used for
passing data between the local process and the Exim process.
This is ``real'' SMTP and is handled in the same way as SMTP over TCP/IP. For
example, the ACLs for SMTP commands are used for this form of submission.

- A local process may also make a TCP/IP call to the host's loopback address
(127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
does not treat the loopback address specially. It treats all such connections
in the same way as connections from other hosts.


cindex:[message sender, constructed by Exim]
cindex:[sender,constructed by Exim]
In the three cases that do not involve TCP/IP, the sender address is
constructed from the login name of the user that called Exim and a default
qualification domain (which can be set by the %qualify_domain% configuration
option). For local or batch SMTP, a sender address that is passed using the
SMTP MAIL command is ignored. However, the system administrator may allow
certain users (``trusted users'') to specify a different sender address
unconditionally, or all users to specify certain forms of different sender
address. The %-f% option or the SMTP MAIL command is used to specify these
different addresses. See section <<SECTtrustedadmin>> for details of trusted
users, and the %untrusted_set_sender% option for a way of allowing untrusted
users to change sender addresses.

Messages received by either of the non-interactive mechanisms are subject to
checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
(either over TCP/IP, or interacting with a local process) can be checked by a
number of ACLs that operate at different times during the SMTP session. Either
individual recipients, or the entire message, can be rejected if local policy
requirements are not met. The 'local_scan()' function (see chapter
<<CHAPlocalscan>>) is run for all incoming messages.

Exim can be configured not to start a delivery process when a message is
received; this can be unconditional, or depend on the number of incoming SMTP
connections or the system load. In these situations, new messages wait on the
queue until a queue runner process picks them up. However, in standard
configurations under normal conditions, delivery is started as soon as a
message is received.





Handling an incoming message
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[spool directory,files that hold a message]
cindex:[file,how a message is held]
When Exim accepts a message, it writes two files in its spool directory. The
first contains the envelope information, the current status of the message, and
the header lines, and the second contains the body of the message. The names of
the two spool files consist of the message id, followed by `-H` for the
file containing the envelope and header, and `-D` for the data file.

cindex:[spool directory,_input_ sub-directory]
By default all these message files are held in a single directory called
_input_ inside the general Exim spool directory. Some operating systems do
not perform very well if the number of files in a directory gets very large; to
improve performance in such cases, the %split_spool_directory% option can be
used. This causes Exim to split up the input files into 62 sub-directories
whose names are single letters or digits.

The envelope information consists of the address of the message's sender and
the addresses of the recipients. This information is entirely separate from
any addresses contained in the header lines. The status of the message includes
a list of recipients who have already received the message. The format of the
first spool file is described in chapter <<CHAPspool>>.

cindex:[rewriting,addresses]
Address rewriting that is specified in the rewrite section of the configuration
(see chapter <<CHAPrewrite>>) is done once and for all on incoming addresses,
both in the header lines and the envelope, at the time the message is accepted.
If during the course of delivery additional addresses are generated (for
example, via aliasing), these new addresses are rewritten as soon as they are
generated. At the time a message is actually delivered (transported) further
rewriting can take place; because this is a transport option, it can be
different for different forms of delivery. It is also possible to specify the
addition or removal of certain header lines at the time the message is
delivered (see chapters <<CHAProutergeneric>> and <<CHAPtransportgeneric>>).



Life of a message
~~~~~~~~~~~~~~~~~
cindex:[message,life of]
cindex:[message,frozen]
A message remains in the spool directory until it is completely delivered to
its recipients or to an error address, or until it is deleted by an
administrator or by the user who originally created it. In cases when delivery
cannot proceed -- for example, when a message can neither be delivered to its
recipients nor returned to its sender, the message is marked ``frozen'' on the
spool, and no more deliveries are attempted.

cindex:[frozen messages,thawing]
cindex:[message,thawing frozen]
An administrator can ``thaw'' such messages when the problem has been corrected,
and can also freeze individual messages by hand if necessary. In addition, an
administrator can force a delivery error, causing a bounce message to be sent.

cindex:[%auto_thaw%]
There is an option called %auto_thaw%, which can be used to cause Exim to
retry frozen messages after a certain time. When this is set, no message will
remain on the queue for ever, because the delivery timeout will eventually be
reached. Delivery failure reports (bounce messages) that reach this timeout are
discarded.

cindex:[%timeout_frozen_after%]
There is also an option called %timeout_frozen_after%, which discards frozen
messages after a certain time.

cindex:[message,log file for]
cindex:[log,file for each message]
While Exim is working on a message, it writes information about each delivery
attempt to the main log file. This includes successful, unsuccessful, and
delayed deliveries for each recipient (see chapter <<CHAPlog>>). The log lines
are also written to a separate 'message log' file for each message. These
logs are solely for the benefit of the administrator, and are normally deleted
along with the spool files when processing of a message is complete.
The use of individual message logs can be disabled by setting
%no_message_logs%; this might give an improvement in performance on very
busy systems.

cindex:[journal file]
cindex:[file,journal]
All the information Exim itself needs to set up a delivery is kept in the first
spool file, along with the header lines. When a successful delivery occurs, the
address is immediately written at the end of a journal file, whose name is the
message id followed by `-J`. At the end of a delivery run, if there are some
addresses left to be tried again later, the first spool file (the `-H` file)
is updated to indicate which these are, and the journal file is then deleted.
Updating the spool file is done by writing a new file and renaming it, to
minimize the possibility of data loss.

Should the system or the program crash after a successful delivery but before
the spool file has been updated, the journal is left lying around. The next
time Exim attempts to deliver the message, it reads the journal file and
updates the spool file before proceeding. This minimizes the chances of double
deliveries caused by crashes.



[[SECTprocaddress]]
Processing an address for delivery
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[drivers,definition of]
cindex:[router,definition of]
cindex:[transport,definition of]
The main delivery processing elements of Exim are called 'routers' and
'transports', and collectively these are known as 'drivers'. Code for a
number of them is provided in the source distribution, and compile-time options
specify which ones are included in the binary. Run time options specify which
ones are actually used for delivering messages.

cindex:[drivers,instance definition]
Each driver that is specified in the run time configuration is an 'instance'
of that particular driver type. Multiple instances are allowed; for example,
you can set up several different ^smtp^ transports, each with different
option values that might specify different ports or different timeouts. Each
instance has its own identifying name. In what follows we will normally use the
instance name when discussing one particular instance (that is, one specific
configuration of the driver), and the generic driver name when discussing
the driver's features in general.

A 'router' is a driver that operates on an address, either determining how
its delivery should happen, by routing it to a specific transport, or
converting the address into one or more new addresses (for example, via an
alias file). A router may also explicitly choose to fail an address, causing it
to be bounced.

A 'transport' is a driver that transmits a copy of the message from Exim's
spool to some destination. There are two kinds of transport: for a 'local'
transport, the destination is a file or a pipe on the local host, whereas for a
'remote' transport the destination is some other host. A message is passed
to a specific transport as a result of successful routing. If a message has
several recipients, it may be passed to a number of different transports.

cindex:[preconditions,definition of]
An address is processed by passing it to each configured router instance in
turn, subject to certain preconditions, until a router accepts the address or
specifies that it should be bounced. We will describe this process in more
detail shortly. As a simple example, the diagram below illustrates how each
recipient address in a message is processed in a small configuration of three
routers that are configured in various ways.

To make this a more concrete example, we'll describe it in terms of some actual
routers, but remember, this is only an example. You can configure Exim's
routers in many different ways, and there may be any number of routers in a
configuration.

The first router that is specified in a configuration is often one that handles
addresses in domains that are not recognized specially by the local host. These
are typically addresses for arbitrary domains on the Internet. A precondition
is set up which looks for the special domains known to the host (for example,
its own domain name), and the router is run for addresses that do 'not'
match. Typically, this is a router that looks up domains in the DNS in order to
find the hosts to which this address routes. If it succeeds, the address is
queued for a suitable SMTP transport; if it does not succeed, the router is
configured to fail the address.

///
The example pictured could be a configuration of this type. The second and
third routers can only be run for addresses for which the preconditions for
the first router are not met. If one of these preconditions checks the
domain, the second and third routers are run only for domains that are somehow
special to the local host.
///

The second router does redirection -- also known as aliasing and forwarding.
When it generates one or more new addresses from the original, each of them is
routed independently from the start. Otherwise, the router may cause an address
to fail, or it may simply decline to handle the address, in which case the
address is passed to the next router.

The final router in many configurations is one that checks to see if the
address belongs to a local mailbox. The precondition may involve a check to
see if the local part is the name of a login account, or it may look up the
local part in a file or a database. If its preconditions are not met, or if
the router declines, we have reached the end of the routers. When this happens,
the address is bounced.



Processing an address for verification
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[router,for verification]
cindex:[verifying address, overview]
As well as being used to decide how to deliver to an address, Exim's routers
are also used for 'address verification'. Verification can be requested as
one of the checks to be performed in an ACL for incoming messages, on both
sender and recipient addresses, and it can be tested using the %-bv% and
%-bvs% command line options.

When an address is being verified, the routers are run in ``verify mode''. This
does not affect the way the routers work, but it is a state that can be
detected. By this means, a router can be skipped or made to behave differently
when verifying. A common example is a configuration in which the first router
sends all messages to a message-scanning program, unless they have been
previously scanned. Thus, the first router accepts all addresses without any
checking, making it useless for verifying. Normally, the %no_verify% option
would be set for such a router, causing it to be skipped in verify mode.




[[SECTrunindrou]]
Running an individual router
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[router,running details]
cindex:[preconditions,checking]
cindex:[router,result of running]
As explained in the example above, a number of preconditions are checked before
running a router. If any are not met, the router is skipped, and the address is
passed to the next router. When all the preconditions on a router 'are' met,
the router is run. What happens next depends on the outcome, which is one of
the following:

- 'accept': The router accepts the address, and either queues it for a
transport, or generates one or more ``child'' addresses. Processing the original
address ceases,
cindex:[%unseen% option]
unless the %unseen% option is set on the router. This option
can be used to set up multiple deliveries with different routing (for example,
for keeping archive copies of messages). When %unseen% is set, the address is
passed to the next router. Normally, however, an 'accept' return marks the
end of routing.
+
cindex:[case of local parts]
cindex:[address duplicate, discarding]
If child addresses are generated, Exim checks to see whether they are
duplicates of any existing recipient addresses. During this check, local parts
are treated as case-sensitive. Duplicate addresses are discarded. Each of the
remaining child addresses is then processed independently, starting with the
first router by default. It is possible to change this by setting the
%redirect_router% option to specify which router to start at for child
addresses. Unlike %pass_router% (see below) the router specified by
%redirect_router% may be anywhere in the router configuration.

- 'pass': The router recognizes the address, but cannot handle it itself. It
requests that the address be passed to another router. By default the address
is passed to the next router, but this can be changed by setting the
%pass_router% option. However, (unlike %redirect_router%) the named router
must be below the current router (to avoid loops).

- 'decline': The router declines to accept the address because it does not
recognize it at all. By default, the address is passed to the next router, but
this can be prevented by setting the %no_more% option. When %no_more% is set,
all the remaining routers are skipped.

- 'fail': The router determines that the address should fail, and queues it for
the generation of a bounce message. There is no further processing of the
original address unless %unseen% is set on the router.

- 'defer': The router cannot handle the address at the present time. (A database
may be offline, or a DNS lookup may have timed out.) No further processing of
the address happens in this delivery attempt. It is tried again next time the
message is considered for delivery.

- 'error': There is some error in the router (for example, a syntax error in
its configuration). The action is as for defer.

If an address reaches the end of the routers without having been accepted by
any of them, it is bounced as unrouteable.
The default error message in this situation is ``unrouteable address'', but you
can set your own message by making use of the %cannot_route_message% option.
This can be set for any router; the value from the last router that ``saw''
the address is used.

Sometimes while routing you want to fail a delivery when some conditions are
met but others are not, instead of passing the address on for further routing.
You can do this by having a second router that explicitly fails the delivery
when the relevant conditions are met. The ^redirect^ router has a ``fail''
facility for this purpose.




[[SECTrouprecon]]
Router preconditions
~~~~~~~~~~~~~~~~~~~~
cindex:[router preconditions, order of processing]
cindex:[preconditions,order of processing]
The preconditions that are tested for each router are listed below, in the
order in which they are tested. The individual configuration options are
described in more detail in chapter <<CHAProutergeneric>>.

- The %local_part_prefix% and %local_part_suffix% options can specify that
the local parts handled by the router may or must have certain prefixes and/or
suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
skipped. These conditions are tested first. When an affix is present, it is
removed from the local part before further processing, including the evaluation
of any other conditions.

- Routers can be designated for use only when not verifying an address, that is,
only when routing it for delivery (or testing its delivery routing). If the
%verify% option is set false, the router is skipped when Exim is verifying an
address.
Setting the %verify% option actually sets two options, %verify_sender% and
%verify_recipient%, which independently control the use of the router for
sender and recipient verification. You can set these options directly if
you want a router to be used for only one type of verification.

- If the %address_test% option is set false, the router is skipped when Exim is
run with the %-bt% option to test an address routing. This can be helpful when
the first router sends all new messages to a scanner of some sort; it makes it
possible to use %-bt% to test subsequent delivery routing without having to
simulate the effect of the scanner.

- Routers can be designated for use only when verifying an address, as
opposed to routing it for delivery. The %verify_only% option controls this.

- Certain routers can be explicitly skipped when running the routers to check an
address given in the SMTP EXPN command (see the %expn% option).

- If the %domains% option is set, the domain of the address must be in the set of
domains that it defines.

- If the %local_parts% option is set, the local part of the address must be in
the set of local parts that it defines. If %local_part_prefix% or
%local_part_suffix% is in use, the prefix or suffix is removed from the local
part before this check. If you want to do precondition tests on local parts
that include affixes, you can do so by using a %condition% option (see below)
that uses the variables $local_part$, $local_part_prefix$, and
$local_part_suffix$ as necessary.

- If the %check_local_user% option is set, the local part must be the name of
an account on the local host.
If this check succeeds, the uid and gid of the local user are placed in
$local_user_uid$ and $local_user_gid$; these values can be used in the
remaining preconditions.

- If the %router_home_directory% option is set, it is expanded at this point,
because it overrides the value of $home$. If this expansion were left till
later, the value of $home$ as set by %check_local_user% would be used in
subsequent tests. Having two different values of $home$ in the same router
could lead to confusion.

- If the %senders% option is set, the envelope sender address must be in the set
of addresses that it defines.

- If the %require_files% option is set, the existence or non-existence of
specified files is tested.

- cindex:[customizing,precondition]
If the %condition% option is set, it is evaluated and tested. This option uses
an expanded string to allow you to set up your own custom preconditions.
Expanded strings are described in chapter <<CHAPexpand>>.


Note that %require_files% comes near the end of the list, so you cannot use it
to check for the existence of a file in which to lookup up a domain, local
part, or sender. However, as these options are all expanded, you can use the
%exists% expansion condition to make such tests within each condition. The
%require_files% option is intended for checking files that the router may be
going to use internally, or which are needed by a specific transport (for
example, _.procmailrc_).



Delivery in detail
~~~~~~~~~~~~~~~~~~
cindex:[delivery,in detail]
When a message is to be delivered, the sequence of events is as follows:

- If a system-wide filter file is specified, the message is passed to it. The
filter may add recipients to the message, replace the recipients, discard the
message, cause a new message to be generated, or cause the message delivery to
fail. The format of the system filter file is the same as for Exim user filter
files, described in the separate document entitled
'Exim's interfaces to mail filtering'.
cindex:[Sieve filter,not available for system filter]
(*Note*: Sieve cannot be used for system filter files.)
+
Some additional features are available in system filters -- see chapter
<<CHAPsystemfilter>> for details. Note that a message is passed to the system
filter only once per delivery attempt, however many recipients it has. However,
if there are several delivery attempts because one or more addresses could not
be immediately delivered, the system filter is run each time. The filter
condition %first_delivery% can be used to detect the first run of the system
filter.

- Each recipient address is offered to each configured router in turn, subject
to its preconditions, until one is able to handle it. If no router can handle
the address, that is, if they all decline, the address is failed. Because
routers can be targeted at particular domains, several locally handled domains
can be processed entirely independently of each other.

- cindex:[routing,loops in]
cindex:[loop,while routing]
A router that accepts an address may set up a local or a remote transport for
it. However, the transport is not run at this time. Instead, the address is
placed on a list for the particular transport, to be run later. Alternatively,
the router may generate one or more new addresses (typically from alias,
forward, or filter files). New addresses are fed back into this process from
the top, but in order to avoid loops, a router ignores any address which has an
identically-named ancestor that was processed by itself.

- When all the routing has been done, addresses that have been successfully
handled are passed to their assigned transports. When local transports are
doing real local deliveries, they handle only one address at a time, but if a
local transport is being used as a pseudo-remote transport (for example, to
collect batched SMTP messages for transmission by some other means) multiple
addresses can be handled. Remote transports can always handle more than one
address at a time, but can be configured not to do so, or to restrict multiple
addresses to the same domain.

- Each local delivery to a file or a pipe runs in a separate process under a
non-privileged uid, and these deliveries are run one at a time. Remote
deliveries also run in separate processes, normally under a uid that is private
to Exim (``the Exim user''), but in this case, several remote deliveries can be
run in parallel. The maximum number of simultaneous remote deliveries for any
one message is set by the %remote_max_parallel% option.
The order in which deliveries are done is not defined, except that all local
deliveries happen before any remote deliveries.

- cindex:[queue runner]
When it encounters a local delivery during a queue run, Exim checks its retry
database to see if there has been a previous temporary delivery failure for the
address before running the local transport. If there was a previous failure,
Exim does not attempt a new delivery until the retry time for the address is
reached. However, this happens only for delivery attempts that are part of a
queue run. Local deliveries are always attempted when delivery immediately
follows message reception, even if retry times are set for them. This makes for
better behaviour if one particular message is causing problems (for example,
causing quota overflow, or provoking an error in a filter file).

- cindex:[delivery,retry in remote transports]
Remote transports do their own retry handling, since an address may be
deliverable to one of a number of hosts, each of which may have a different
retry time. If there have been previous temporary failures and no host has
reached its retry time, no delivery is attempted, whether in a queue run or
not. See chapter <<CHAPretry>> for details of retry strategies.

- If there were any permanent errors, a bounce message is returned to an
appropriate address (the sender in the common case), with details of the error
for each failing address. Exim can be configured to send copies of bounce
messages to other addresses.

- cindex:[delivery,deferral]
If one or more addresses suffered a temporary failure, the message is left on
the queue, to be tried again later. Delivery of these addresses is said to be
'deferred'.

- When all the recipient addresses have either been delivered or bounced,
handling of the message is complete. The spool files and message log are
deleted, though the message log can optionally be preserved if required.




Retry mechanism
~~~~~~~~~~~~~~~
cindex:[delivery,retry mechanism]
cindex:[retry,description of mechanism]
cindex:[queue runner]
Exim's mechanism for retrying messages that fail to get delivered at the first
attempt is the queue runner process. You must either run an Exim daemon that
uses the %-q% option with a time interval to start queue runners at regular
intervals, or use some other means (such as 'cron') to start them. If you do
not arrange for queue runners to be run, messages that fail temporarily at the
first attempt will remain on your queue for ever. A queue runner process works
it way through the queue, one message at a time, trying each delivery that has
passed its retry time.
You can run several queue runners at once.

Exim uses a set of configured rules to determine when next to retry the failing
address (see chapter <<CHAPretry>>). These rules also specify when Exim should
give up trying to deliver to the address, at which point it generates a bounce
message. If no retry rules are set for a particular host, address, and error
combination, no retries are attempted, and temporary errors are treated as
permanent.



Temporary delivery failure
~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[delivery,temporary failure]
There are many reasons why a message may not be immediately deliverable to a
particular address. Failure to connect to a remote machine (because it, or the
connection to it, is down) is one of the most common. Temporary failures may be
detected during routing as well as during the transport stage of delivery.
Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
is on a file system where the user is over quota. Exim can be configured to
impose its own quotas on local mailboxes; where system quotas are set they will
also apply.

If a host is unreachable for a period of time, a number of messages may be
waiting for it by the time it recovers, and sending them in a single SMTP
connection is clearly beneficial. Whenever a delivery to a remote host is
deferred,

cindex:[hints database]
Exim makes a note in its hints database, and whenever a successful
SMTP delivery has happened, it looks to see if any other messages are waiting
for the same host. If any are found, they are sent over the same SMTP
connection, subject to a configuration limit as to the maximum number in any
one connection.




Permanent delivery failure
~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[delivery,permanent failure]
cindex:[bounce message,when generated]
When a message cannot be delivered to some or all of its intended recipients, a
bounce message is generated. Temporary delivery failures turn into permanent
errors when their timeout expires. All the addresses that fail in a given
delivery attempt are listed in a single message. If the original message has
many recipients, it is possible for some addresses to fail in one delivery
attempt and others to fail subsequently, giving rise to more than one bounce
message. The wording of bounce messages can be customized by the administrator.
See chapter <<CHAPemsgcust>> for details.

cindex:['X-Failed-Recipients:' header line]
Bounce messages contain an 'X-Failed-Recipients:' header line that lists the
failed addresses, for the benefit of programs that try to analyse such messages
automatically.

cindex:[bounce message,recipient of]
A bounce message is normally sent to the sender of the original message, as
obtained from the message's envelope. For incoming SMTP messages, this is the
address given in the MAIL command. However, when an address is
expanded via a forward or alias file, an alternative address can be specified
for delivery failures of the generated addresses. For a mailing list expansion
(see section <<SECTmailinglists>>) it is common to direct bounce messages to the
manager of the list.




Failures to deliver bounce messages
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[bounce message,failure to deliver]
If a bounce message (either locally generated or received from a remote host)
itself suffers a permanent delivery failure, the message is left on the queue,
but it is frozen, awaiting the attention of an administrator. There are options
which can be used to make Exim discard such failed messages, or to keep them
for only a short time (see %timeout_frozen_after% and
%ignore_bounce_errors_after%).





////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////

Building and installing Exim
----------------------------

cindex:[building Exim]

Unpacking
~~~~~~~~~
Exim is distributed as a gzipped or bzipped tar file which, when upacked,
creates a directory with the name of the current release (for example,
_exim-{version}_) into which the following files are placed:

[frame="none"]
`--------------------`--------------------------------------------------------
_ACKNOWLEDGMENTS_    contains some acknowledgments
_CHANGES_            contains a reference to where changes are documented
_LICENCE_            the GNU General Public Licence
_Makefile_           top-level make file
_NOTICE_             conditions for the use of Exim
_README_             list of files, directories and simple build instructions
------------------------------------------------------------------------------

Other files whose names begin with _README_ may also be present. The
following subdirectories are created:

[frame="none"]
`--------------------`------------------------------------------------
_Local_              an empty directory for local configuration files
_OS_                 OS-specific files
_doc_                documentation files
_exim_monitor_       source files for the Exim monitor
_scripts_            scripts used in the build process
_src_                remaining source files
_util_               independent utilities
----------------------------------------------------------------------

The main utility programs are contained in the _src_ directory, and are built
with the Exim binary. The _util_ directory contains a few optional scripts
that may be useful to some sites.


Multiple machine architectures and operating systems
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[building Exim,multiple OS/architectures]
The building process for Exim is arranged to make it easy to build binaries for
a number of different architectures and operating systems from the same set of
source files. Compilation does not take place in the _src_ directory. Instead,
a 'build directory' is created for each architecture and operating system.

cindex:[symbolic link,to build directory]
Symbolic links to the sources are installed in this directory, which is where
the actual building takes place.

In most cases, Exim can discover the machine architecture and operating system
for itself, but the defaults can be overridden if necessary.


[[SECTdb]]
DBM libraries
~~~~~~~~~~~~~
cindex:[DBM libraries, discussion of]
cindex:[hints database,DBM files used for]
Even if you do not use any DBM files in your configuration, Exim still needs a
DBM library in order to operate, because it uses indexed files for its hints
databases. Unfortunately, there are a number of DBM libraries in existence, and
different operating systems often have different ones installed.

cindex:[Solaris,DBM library for]
cindex:[IRIX, DBM library for]
cindex:[BSD, DBM library for]
cindex:[Linux, DBM library for]
If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
Linux distribution, the DBM configuration should happen automatically, and you
may be able to ignore this section. Otherwise, you may have to learn more than
you would like about DBM libraries from what follows.

cindex:['ndbm' DBM library]
Licensed versions of Unix normally contain a library of DBM functions operating
via the 'ndbm' interface, and this is what Exim expects by default. Free
versions of Unix seem to vary in what they contain as standard. In particular,
some early versions of Linux have no default DBM library, and different
distributors have chosen to bundle different libraries with their packaged
versions. However, the more recent releases seem to have standardised on the
Berkeley DB library.

Different DBM libraries have different conventions for naming the files they
use. When a program opens a file called _dbmfile_, there are four
possibilities:

. A traditional 'ndbm' implementation, such as that supplied as part of
Solaris, operates on two files called _dbmfile.dir_ and _dbmfile.pag_.

. cindex:['gdbm' DBM library]
The GNU library, 'gdbm', operates on a single file. If used via its 'ndbm'
compatibility interface it makes two different hard links to it with names
_dbmfile.dir_ and _dbmfile.pag_, but if used via its native interface, the
file name is used unmodified.

. cindex:[Berkeley DB library]
The Berkeley DB package, if called via its 'ndbm' compatibility interface,
operates on a single file called _dbmfile.db_, but otherwise looks to the
programmer exactly the same as the traditional 'ndbm' implementation.

. If the Berkeley package is used in its native mode, it operates on a single
file called _dbmfile_; the programmer's interface is somewhat different to
the traditional 'ndbm' interface.

. To complicate things further, there are several very different versions of the
Berkeley DB package. Version 1.85 was stable for a very long time, releases
2.'x' and 3.'x' were current for a while, but the latest versions are now
numbered 4.'x'. Maintenance of some of the earlier releases has ceased. All
versions of Berkeley DB can be obtained from
+
&&&
*http://www.sleepycat.com/[]*
&&&

. cindex:['tdb' DBM library]
Yet another DBM library, called 'tdb', has become available from
+
&&&
*http://download.sourceforge.net/tdb[]*
&&&
+
It has its own interface, and also operates on a single file.

cindex:[USE_DB]
cindex:[DBM libraries, configuration for building]
Exim and its utilities can be compiled to use any of these interfaces. In order
to use any version of the Berkeley DB package in native mode, you must set
USE_DB in an appropriate configuration file (typically
_Local/Makefile_). For example:

  USE_DB=yes

Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
error is diagnosed if you set more than one of these.

At the lowest level, the build-time configuration sets none of these options,
thereby assuming an interface of type (1). However, some operating system
configuration files (for example, those for the BSD operating systems and
Linux) assume type (4) by setting USE_DB as their default, and the
configuration files for Cygwin set USE_GDBM. Anything you set in
_Local/Makefile_, however, overrides these system defaults.

As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
necessary to set DBMLIB, to cause inclusion of the appropriate library, as
in one of these lines:

  DBMLIB = -ldb
  DBMLIB = -ltdb

Settings like that will work if the DBM library is installed in the standard
place. Sometimes it is not, and the library's header file may also not be in
the default path. You may need to set INCLUDE to specify where the header
file is, and to specify the path to the library more fully in DBMLIB, as in
this example:

  INCLUDE=-I/usr/local/include/db-4.1
  DBMLIB=/usr/local/lib/db-4.1/libdb.a


There is further detailed discussion about the various DBM libraries in the
file _doc/dbm.discuss.txt_ in the Exim distribution.



Pre-building configuration
~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[building Exim,pre-building configuration]
cindex:[configuration for building Exim]
cindex:[_Local/Makefile_]
cindex:[_src/EDITME_]
Before building Exim, a local configuration file that specifies options
independent of any operating system has to be created with the name
_Local/Makefile_. A template for this file is supplied as the file
_src/EDITME_, and it contains full descriptions of all the option settings
therein. These descriptions are therefore not repeated here. If you are
building Exim for the first time, the simplest thing to do is to copy
_src/EDITME_ to _Local/Makefile_, then read it and edit it appropriately.

There are three settings that you must supply, because Exim will not build
without them. They are the location of the run time configuration file
(CONFIGURE_FILE), the directory in which Exim binaries will be installed
(BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
a colon-separated list of file names; Exim uses the first of them that exists.

There are a few other parameters that can be specified either at build time or
at run time, to enable the same binary to be used on a number of different
machines. However, if the locations of Exim's spool directory and log file
directory (if not within the spool directory) are fixed, it is recommended that
you specify them in _Local/Makefile_ instead of at run time, so that errors
detected early in Exim's execution (such as a malformed configuration file) can
be logged.

cindex:[content scanning,specifying at build time]
Exim's interfaces for calling virus and spam scanning sofware directly from
access control lists are not compiled by default. If you want to include these
facilities, you need to set

  WITH_CONTENT_SCAN=yes

in your _Local/Makefile_. For details of the facilities themselves, see
chapter <<CHAPexiscan>>.


cindex:[_Local/eximon.conf_]
cindex:[_exim_monitor/EDITME_]
If you are going to build the Exim monitor, a similar configuration process is
required. The file _exim_monitor/EDITME_ must be edited appropriately for
your installation and saved under the name _Local/eximon.conf_. If you are
happy with the default settings described in _exim_monitor/EDITME_,
_Local/eximon.conf_ can be empty, but it must exist.

This is all the configuration that is needed in straightforward cases for known
operating systems. However, the building process is set up so that it is easy
to override options that are set by default or by operating-system-specific
configuration files, for example to change the name of the C compiler, which
defaults to %gcc%. See section <<SECToverride>> below for details of how to do
this.



Support for iconv()
~~~~~~~~~~~~~~~~~~~
cindex:['iconv()' support]
The contents of header lines in messages may be encoded according to the rules
described RFC 2047. This makes it possible to transmit characters that are not
in the ASCII character set, and to label them as being in a particular
character set. When Exim is inspecting header lines by means of the %\$h_%
mechanism, it decodes them, and translates them into a specified character set
(default ISO-8859-1). The translation is possible only if the operating system
supports the 'iconv()' function.

However, some of the operating systems that supply 'iconv()' do not support
very many conversions. The GNU %libiconv% library (available from
*http://www.gnu.org/software/libiconv/[]*) can be installed on such systems to
remedy this deficiency, as well as on systems that do not supply 'iconv()' at
all. After installing %libiconv%, you should add

  HAVE_ICONV=yes

to your _Local/Makefile_ and rebuild Exim.



[[SECTinctlsssl]]
Including TLS/SSL encryption support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[TLS,including support for TLS]
cindex:[encryption,including support for]
cindex:[SUPPORT_TLS]
cindex:[OpenSSL,building Exim with]
cindex:[GnuTLS,building Exim with]
Exim can be built to support encrypted SMTP connections, using the STARTTLS
command as per RFC 2487. It can also support legacy clients that expect to
start a TLS session immediately on connection to a non-standard port (see the
%tls_on_connect_ports% runtime option and the %-tls-on-connect% command
line option).

If you want to build Exim with TLS support, you must first install either the
OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
implementing SSL.

If OpenSSL is installed, you should set

  SUPPORT_TLS=yes
  TLS_LIBS=-lssl -lcrypto

in _Local/Makefile_. You may also need to specify the locations of the
OpenSSL library and include files. For example:

  SUPPORT_TLS=yes
  TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
  TLS_INCLUDE=-I/usr/local/openssl/include/

cindex:[USE_GNUTLS]
If GnuTLS is installed, you should set

  SUPPORT_TLS=yes
  USE_GNUTLS=yes
  TLS_LIBS=-lgnutls -ltasn1 -lgcrypt

in _Local/Makefile_, and again you may need to specify the locations of the
library and include files. For example:

  SUPPORT_TLS=yes
  USE_GNUTLS=yes
  TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
  TLS_INCLUDE=-I/usr/gnu/include

You do not need to set TLS_INCLUDE if the relevant directory is already
specified in INCLUDE. Details of how to configure Exim to make use of TLS
are given in chapter <<CHAPTLS>>.




Use of tcpwrappers
~~~~~~~~~~~~~~~~~~
cindex:[tcpwrappers, building Exim to support]
cindex:[USE_TCP_WRAPPERS]
Exim can be linked with the 'tcpwrappers' library in order to check incoming
SMTP calls using the 'tcpwrappers' control files. This may be a convenient
alternative to Exim's own checking facilities for installations that are
already making use of 'tcpwrappers' for other purposes. To do this, you should
set USE_TCP_WRAPPERS in _Local/Makefile_, arrange for the file
_tcpd.h_ to be available at compile time, and also ensure that the library
_libwrap.a_ is available at link time, typically by including %-lwrap% in
EXTRALIBS_EXIM. For example, if 'tcpwrappers' is installed in
_/usr/local_, you might have

  USE_TCP_WRAPPERS=yes
  CFLAGS=-O -I/usr/local/include
  EXTRALIBS_EXIM=-L/usr/local/lib -lwrap

in _Local/Makefile_. The name to use in the 'tcpwrappers' control files is
``exim''. For example, the line

  exim : LOCAL  192.168.1.  .friendly.domain.example

in your _/etc/hosts.allow_ file allows connections from the local host, from
the subnet 192.168.1.0/24, and from all hosts in 'friendly.domain.example'.
All other connections are denied. Consult the 'tcpwrappers' documentation for
further details.



Including support for IPv6
~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[IPv6,including support for]
Exim contains code for use on systems that have IPv6 support. Setting
`HAVE_IPV6=YES` in _Local/Makefile_ causes the IPv6 code to be included;
it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
where the IPv6 support is not fully integrated into the normal include and
library files.

Two different types of DNS record for handling IPv6 addresses have been
defined. AAAA records (analagous to A records for IPv4) are in use, and are
currently seen as the mainstream. Another record type called A6 was proposed
as better than AAAA because it had more flexibility. However, it was felt to be
over-complex, and its status was reduced to ``experimental''. It is not known
if anyone is actually using A6 records. Exim has support for A6 records, but
this is included only if you set `SUPPORT_A6=YES` in _Local/Makefile_. The
support has not been tested for some time.



The building process
~~~~~~~~~~~~~~~~~~~~
cindex:[build directory]
Once _Local/Makefile_ (and _Local/eximon.conf_, if required) have been
created, run 'make' at the top level. It determines the architecture and
operating system types, and creates a build directory if one does not exist.
For example, on a Sun system running Solaris 8, the directory
_build-SunOS5-5.8-sparc_ is created.
cindex:[symbolic link,to source files]
Symbolic links to relevant source files are installed in the build directory.

*Warning*: The %-j% (parallel) flag must not be used with 'make'; the
building process fails if it is set.

If this is the first time 'make' has been run, it calls a script that builds
a make file inside the build directory, using the configuration files from the
_Local_ directory. The new make file is then passed to another instance of
'make'. This does the real work, building a number of utility scripts, and
then compiling and linking the binaries for the Exim monitor (if configured), a
number of utility programs, and finally Exim itself. The command 'make
makefile' can be used to force a rebuild of the make file in the build
directory, should this ever be necessary.

If you have problems building Exim, check for any comments there may be in the
_README_ file concerning your operating system, and also take a look at the
FAQ, where some common problems are covered.




[[SECToverride]]
Overriding build-time options for Exim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[build-time options, overriding]
The main make file that is created at the beginning of the building process
consists of the concatenation of a number of files which set configuration
values, followed by a fixed set of 'make' instructions. If a value is set
more than once, the last setting overrides any previous ones. This provides a
convenient way of overriding defaults. The files that are concatenated are, in
order:

&&&
_OS/Makefile-Default_
_OS/Makefile-_<'ostype'>
_Local/Makefile_
_Local/Makefile-_<'ostype'>
_Local/Makefile-_<'archtype'>
_Local/Makefile-_<'ostype'>-<'archtype'>
_OS/Makefile-Base_
&&&

cindex:[_Local/Makefile_]
cindex:[building Exim,operating system type]
cindex:[building Exim,architecture type]
where <'ostype'> is the operating system type and <'archtype'> is the
architecture type. _Local/Makefile_ is required to exist, and the building
process fails if it is absent. The other three _Local_ files are optional,
and are often not needed.

The values used for <'ostype'> and <'archtype'> are obtained from scripts
called _scripts/os-type_ and _scripts/arch-type_ respectively. If either of
the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
values are used, thereby providing a means of forcing particular settings.
Otherwise, the scripts try to get values from the %uname% command. If this
fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
of 'ad hoc' transformations are then applied, to produce the standard names
that Exim expects. You can run these scripts directly from the shell in order
to find out what values are being used on your system.


_OS/Makefile-Default_ contains comments about the variables that are set
therein. Some (but not all) are mentioned below. If there is something that
needs changing, review the contents of this file and the contents of the make
file for your operating system (_OS/Makefile-<ostype>_) to see what the
default values are.


cindex:[building Exim,overriding default settings]
If you need to change any of the values that are set in _OS/Makefile-Default_
or in _OS/Makefile-<ostype>_, or to add any new definitions, you do not
need to change the original files. Instead, you should make the changes by
putting the new values in an appropriate _Local_ file. For example,
cindex:[Tru64-Unix build-time settings]
when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
formerly DEC-OSF1) operating system, it is necessary to specify that the C
compiler is called 'cc' rather than 'gcc'. Also, the compiler must be
called with the option %-std1%, to make it recognize some of the features of
Standard C that Exim uses. (Most other compilers recognize Standard C by
default.) To do this, you should create a file called _Local/Makefile-OSF1_
containing the lines

  CC=cc
  CFLAGS=-std1

If you are compiling for just one operating system, it may be easier to put
these lines directly into _Local/Makefile_.

Keeping all your local configuration settings separate from the distributed
files makes it easy to transfer them to new versions of Exim simply by copying
the contents of the _Local_ directory.


cindex:[NIS lookup type,including support for]
cindex:[NIS+ lookup type,including support for]
cindex:[LDAP,including support for]
cindex:[lookup,inclusion in binary]
Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
lookup, but not all systems have these components installed, so the default is
not to include the relevant code in the binary. All the different kinds of file
and database lookup that Exim supports are implemented as separate code modules
which are included only if the relevant compile-time options are set. In the
case of LDAP, NIS, and NIS+, the settings for _Local/Makefile_ are:

  LOOKUP_LDAP=yes
  LOOKUP_NIS=yes
  LOOKUP_NISPLUS=yes

and similar settings apply to the other lookup types. They are all listed in
_src/EDITME_. In most cases the relevant include files and interface
libraries need to be installed before compiling Exim.
cindex:[cdb,including support for]
However, in the case of cdb, which is included in the binary only if

  LOOKUP_CDB=yes

is set, the code is entirely contained within Exim, and no external include
files or libraries are required. When a lookup type is not included in the
binary, attempts to configure Exim to use it cause run time configuration
errors.

cindex:[Perl,including support for]
Exim can be linked with an embedded Perl interpreter, allowing Perl
subroutines to be called during string expansion. To enable this facility,

  EXIM_PERL=perl.o

must be defined in _Local/Makefile_. Details of this facility are given in
chapter <<CHAPperl>>.

cindex:[X11 libraries, location of]
The location of the X11 libraries is something that varies a lot between
operating systems, and of course there are different versions of X11 to cope
with. Exim itself makes no use of X11, but if you are compiling the Exim
monitor, the X11 libraries must be available.
The following three variables are set in _OS/Makefile-Default_:

  X11=/usr/X11R6
  XINCLUDE=-I$(X11)/include
  XLFLAGS=-L$(X11)/lib

These are overridden in some of the operating-system configuration files. For
example, in _OS/Makefile-SunOS5_ there is

  X11=/usr/openwin
  XINCLUDE=-I$(X11)/include
  XLFLAGS=-L$(X11)/lib -R$(X11)/lib

If you need to override the default setting for your operating system, place a
definition of all three of these variables into your
_Local/Makefile-<ostype>_ file.

cindex:[EXTRALIBS]
If you need to add any extra libraries to the link steps, these can be put in a
variable called EXTRALIBS, which appears in all the link commands, but by
default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
command for linking the main Exim binary, and not for any associated utilities.

cindex:[DBM libraries, configuration for building]
There is also DBMLIB, which appears in the link commands for binaries that
use DBM functions (see also section <<SECTdb>>). Finally, there is
EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
binary, and which can be used, for example, to include additional X11
libraries.

cindex:[configuration file,editing]
The make file copes with rebuilding Exim correctly if any of the configuration
files are edited. However, if an optional configuration file is deleted, it is
necessary to touch the associated non-optional file (that is, _Local/Makefile_
or _Local/eximon.conf_) before rebuilding.


OS-specific header files
~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[_os.h_]
cindex:[building Exim,OS-specific C header files]
The _OS_ directory contains a number of files with names of the form
_os.h-<ostype>_. These are system-specific C header files that should not
normally need to be changed. There is a list of macro settings that are
recognized in the file _OS/os.configuring_, which should be consulted if you
are porting Exim to a new operating system.



Overriding build-time options for the monitor
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[building Eximon,overriding default options]
A similar process is used for overriding things when building the Exim monitor,
where the files that are involved are

&&&
_OS/eximon.conf-Default_
_OS/eximon.conf-_<'ostype'>
_Local/eximon.conf_
_Local/eximon.conf-_<'ostype'>
_Local/eximon.conf-_<'archtype'>
_Local/eximon.conf-_<'ostype'>-<'archtype'>
&&&

cindex:[_Local/eximon.conf_]
As with Exim itself, the final three files need not exist, and in this case the
_OS/eximon.conf-<ostype>_ file is also optional. The default values in
_OS/eximon.conf-Default_ can be overridden dynamically by setting environment
variables of the same name, preceded by EXIMON_. For example, setting
EXIMON_LOG_DEPTH in the environment overrides the value of
LOG_DEPTH at run time.




Installing Exim binaries and scripts
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[installing Exim]
cindex:[BIN_DIRECTORY]
The command 'make install' runs the 'exim_install' script with no
arguments. The script copies binaries and utility scripts into the directory
whose name is specified by the BIN_DIRECTORY setting in
_Local/Makefile_.

cindex:[CONFIGURE_FILE]
Exim's run time configuration file is named by the CONFIGURE_FILE setting
in _Local/Makefile_. If this names a single file, and the file does not
exist, the default configuration file _src/configure.default_ is copied there
by the installation script. If a run time configuration file already exists, it
is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
alternative files, no default is installed.

cindex:[system aliases file]
cindex:[_/etc/aliases_]
One change is made to the default configuration file when it is installed: the
default configuration contains a router that references a system aliases file.
The path to this file is set to the value specified by
SYSTEM_ALIASES_FILE in _Local/Makefile_ (_/etc/aliases_ by default).
If the system aliases file does not exist, the installation script creates it,
and outputs a comment to the user.

The created file contains no aliases, but it does contain comments about the
aliases a site should normally have. Mail aliases have traditionally been
kept in _/etc/aliases_. However, some operating systems are now using
_/etc/mail/aliases_. You should check if yours is one of these, and change
Exim's configuration if necessary.

The default configuration uses the local host's name as the only local domain,
and is set up to do local deliveries into the shared directory _/var/mail_,
running as the local user. System aliases and _.forward_ files in users' home
directories are supported, but no NIS or NIS+ support is configured. Domains
other than the name of the local host are routed using the DNS, with delivery
over SMTP.

cindex:[setuid,installing Exim with]
The install script copies files only if they are newer than the files they are
going to replace. The Exim binary is required to be owned by root and have the
'setuid' bit set, for normal configurations. Therefore, you must run 'make
install' as root so that it can set up the Exim binary in this way. However, in
some special situations (for example, if a host is doing no local deliveries)
it may be possible to run Exim without making the binary setuid root (see
chapter <<CHAPsecurity>> for details).

It is possible to install Exim for special purposes (such as building a binary
distribution) in a private part of the file system. You can do this by a
command such as

  make DESTDIR=/some/directory/ install

This has the effect of pre-pending the specified directory to all the file
paths, except the name of the system aliases file that appears in the default
configuration. (If a default alias file is created, its name 'is' modified.)
For backwards compatibility, ROOT is used if DESTDIR is not set,
but this usage is deprecated.

cindex:[installing Exim,what is not installed]
Running 'make install' does not copy the Exim 4 conversion script
'convert4r4', or the 'pcretest' test program. You will probably run the
first of these only once (if you are upgrading from Exim 3), and the second
isn't really part of Exim. None of the documentation files in the _doc_
directory are copied, except for the info files when you have set
INFO_DIRECTORY, as described in section <<SECTinsinfdoc>> below.

For the utility programs, old versions are renamed by adding the suffix _.O_
to their names. The Exim binary itself, however, is handled differently. It is
installed under a name that includes the version number and the compile number,
for example _exim-{version}-1_. The script then arranges for a symbolic link
called _exim_ to point to the binary. If you are updating a previous version
of Exim, the script takes care to ensure that the name _exim_ is never absent
from the directory (as seen by other processes).

cindex:[installing Exim,testing the script]
If you want to see what the 'make install' will do before running it for
real, you can pass the %-n% option to the installation script by this command:

  make INSTALL_ARG=-n install

The contents of the variable INSTALL_ARG are passed to the installation
script. You do not need to be root to run this test. Alternatively, you can run
the installation script directly, but this must be from within the build
directory. For example, from the top-level Exim directory you could use this
command:

  (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)

cindex:[installing Exim,install script options]
There are two other options that can be supplied to the installation script.

- %-no_chown% bypasses the call to change the owner of the installed binary
to root, and the call to make it a setuid binary.

- %-no_symlink% bypasses the setting up of the symbolic link _exim_ to the
installed binary.

INSTALL_ARG can be used to pass these options to the script. For example:

  make INSTALL_ARG=-no_symlink install


The installation script can also be given arguments specifying which files are
to be copied. For example, to install just the Exim binary, and nothing else,
without creating the symbolic link, you could use:

  make INSTALL_ARG='-no_symlink exim' install




[[SECTinsinfdoc]]
Installing info documentation
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[installing Exim,'info' documentation]
Not all systems use the GNU 'info' system for documentation, and for this
reason, the Texinfo source of Exim's documentation is not included in the main
distribution. Instead it is available separately from the ftp site (see section
<<SECTavail>>).

If you have defined INFO_DIRECTORY in _Local/Makefile_ and the Texinfo
source of the documentation is found in the source tree, running 'make
install' automatically builds the info files and installs them.



Setting up the spool directory
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[spool directory,creating]
When it starts up, Exim tries to create its spool directory if it does not
exist. The Exim uid and gid are used for the owner and group of the spool
directory. Sub-directories are automatically created in the spool directory as
necessary.




Testing
~~~~~~~
cindex:[testing,installation]
Having installed Exim, you can check that the run time configuration file is
syntactically valid by running the following command, which assumes that the
Exim binary directory is within your PATH environment variable:

  exim -bV

If there are any errors in the configuration file, Exim outputs error messages.
Otherwise it outputs the version number and build date,
the DBM library that is being used, and information about which drivers and
other optional code modules are included in the binary.
Some simple routing tests can be done by using the address testing option. For
example,

  exim -bt <local username>

should verify that it recognizes a local mailbox, and

  exim -bt <remote address>

a remote one. Then try getting it to deliver mail, both locally and remotely.
This can be done by passing messages directly to Exim, without going through a
user agent. For example:

  exim -v postmaster@your.domain.example
  From: user@your.domain.example
  To: postmaster@your.domain.example
  Subject: Testing Exim

  This is a test message.
  ^D

The %-v% option causes Exim to output some verification of what it is doing.
In this case you should see copies of three log lines, one for the message's
arrival, one for its delivery, and one containing ``Completed''.

cindex:[delivery,problems with]
If you encounter problems, look at Exim's log files ('mainlog' and
'paniclog') to see if there is any relevant information there. Another source
of information is running Exim with debugging turned on, by specifying the
%-d% option. If a message is stuck on Exim's spool, you can force a delivery
with debugging turned on by a command of the form

  exim -d -M <message-id>

You must be root or an ``admin user'' in order to do this. The %-d% option
produces rather a lot of output, but you can cut this down to specific areas.
For example, if you use %-d-all+route% only the debugging information relevant
to routing is included. (See the %-d% option in chapter <<CHAPcommandline>> for
more details.)

cindex:[``sticky'' bit]
cindex:[lock files]
One specific problem that has shown up on some sites is the inability to do
local deliveries into a shared mailbox directory, because it does not have the
``sticky bit'' set on it. By default, Exim tries to create a lock file before
writing to a mailbox file, and if it cannot create the lock file, the delivery
is deferred. You can get round this either by setting the ``sticky bit'' on the
directory, or by setting a specific group for local deliveries and allowing
that group to create files in the directory (see the comments above the
^local_delivery^ transport in the default configuration file). Another
approach is to configure Exim not to use lock files, but just to rely on
'fcntl()' locking instead. However, you should do this only if all user
agents also use 'fcntl()' locking. For further discussion of locking issues,
see chapter <<CHAPappendfile>>.

One thing that cannot be tested on a system that is already running an MTA is
the receipt of incoming SMTP mail on the standard SMTP port. However, the
%-oX% option can be used to run an Exim daemon that listens on some other
port, or 'inetd' can be used to do this. The %-bh% option and the
'exim_checkaccess' utility can be used to check out policy controls on
incoming SMTP mail.

Testing a new version on a system that is already running Exim can most easily
be done by building a binary with a different CONFIGURE_FILE setting. From
within the run time configuration, all other file and directory names
that Exim uses can be altered, in order to keep it entirely clear of the
production version.


Replacing another MTA with Exim
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[replacing another MTA]
Building and installing Exim for the first time does not of itself put it in
general use. The name by which the system's MTA is called by mail user agents
is either _/usr/sbin/sendmail_, or _/usr/lib/sendmail_ (depending on the
operating system), and it is necessary to make this name point to the 'exim'
binary in order to get the user agents to pass messages to Exim. This is
normally done by renaming any existing file and making _/usr/sbin/sendmail_
or _/usr/lib/sendmail_

cindex:[symbolic link,to 'exim' binary]
a symbolic link to the 'exim' binary. It is a good idea to remove any setuid
privilege and executable status from the old MTA. It is then necessary to stop
and restart the mailer daemon, if one is running.

cindex:[FreeBSD, MTA indirection]
cindex:[_/etc/mail/mailer.conf_]
Some operating systems have introduced alternative ways of switching MTAs. For
example, if you are running FreeBSD, you need to edit the file
_/etc/mail/mailer.conf_ instead of setting up a symbolic link as just
described. A typical example of the contents of this file for running Exim is
as follows:

  sendmail            /usr/exim/bin/exim
  send-mail           /usr/exim/bin/exim
  mailq               /usr/exim/bin/exim -bp
  newaliases          /usr/bin/true


Once you have set up the symbolic link, or edited _/etc/mail/mailer.conf_,
your Exim installation is ``live''. Check it by sending a message from your
favourite user agent.

You should consider what to tell your users about the change of MTA. Exim may
have different capabilities to what was previously running, and there are
various operational differences such as the text of messages produced by
command line options and in bounce messages. If you allow your users to make
use of Exim's filtering capabilities, you should make the document entitled
'Exim's interface to mail filtering'
available to them.



Upgrading Exim
~~~~~~~~~~~~~~
cindex:[upgrading Exim]
If you are already running Exim on your host, building and installing a new
version automatically makes it available to MUAs, or any other programs that
call the MTA directly. However, if you are running an Exim daemon, you do need
to send it a HUP signal, to make it re-exec itself, and thereby pick up the new
binary. You do not need to stop processing mail in order to install a new
version of Exim.



Stopping the Exim daemon on Solaris
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:[Solaris,stopping Exim on]
The standard command for stopping the mailer daemon on Solaris is

  /etc/init.d/sendmail stop

If _/usr/lib/sendmail_ has been turned into a symbolic link, this script
fails to stop Exim because it uses the command 'ps -e' and greps the output
for the text ``sendmail''; this is not present because the actual program name
(that is, ``exim'') is given by the 'ps' command with these options. A solution
is to replace the line that finds the process id with something like

  pid=`cat /var/spool/exim/exim-daemon.pid`

to obtain the daemon's pid directly from the file that Exim saves it in.

Note, however, that stopping the daemon does not ``stop Exim''. Messages can
still be received from local processes, and if automatic delivery is configured
(the normal case), deliveries will still occur.




////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////////

[[CHAPcommandline]]
The Exim command line
---------------------
cindex:[command line,options]
cindex:[options,command line]
Exim's command line takes the standard Unix form of a sequence of options,
each starting with a hyphen character, followed by a number of arguments. The
options are compatible with the main options of Sendmail, and there are also
some additional options, some of which are compatible with Smail 3. Certain
combinations of options do not make sense, and provoke an error if used.
The form of the arguments depends on which options are set.


Setting options by program name
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cindex:['mailq']
If Exim is called under the name 'mailq', it behaves as if the option %-bp%
were present before any other options.
The %-bp% option requests a listing of the contents of the mail queue on the
standard output.
This feature is for compatibility with some systems that contain a command of
that name in one of the standard libraries, symbolically linked to
_/usr/sbin/sendmail_ or _/usr/lib/sendmail_.

cindex:['rsmtp']
If Exim is called under the name 'rsmtp' it behaves as if the option %-bS%
were present before any other options, for compatibility with Smail. The %-bS%
option is used for reading in a number of messages in batched SMTP format.

cindex:['rmail']
If Exim is called under the name 'rmail' it behaves as if the %-i% and
%-oee% options were present before any other options, for compatibility with
Smail. The name 'rmail' is used as an interface by some UUCP systems.

cindex:['runq']
cindex:[queue runner]
If Exim is called under the name 'runq' it behaves as if the option %-q% were
present before any other options, for compatibility with Smail. The %-q%
option causes a single queue runner process to be started.

cindex:['newaliases']
cindex:[alias file,building]
cindex:[Sendmail compatibility,calling Exim as 'newaliases']
If Exim is called under the name 'newaliases' it behaves as if the option
%-bi% were present before any other options, for compatibility with Sendmail.
This option is used for rebuilding Sendmail's alias file. Exim does not have
the concept of a single alias file, but can be configured to run a given
command if called with the %-bi% option.


[[SECTtrustedadmin]]
Trusted and admin users
~~~~~~~~~~~~~~~~~~~~~~~
Some Exim options are available only to 'trusted users' and others are
available only to 'admin users'. In the description below, the phrases ``Exim
user'' and ``Exim group'' mean the user and group defined by EXIM_USER and
EXIM_GROUP in _Local/Makefile_ or set by the %exim_user% and
%exim_group% options. These do not necessarily have to use the name ``exim''.

- cindex:[trusted user,definition of]
cindex:[user, trusted definition of]
The trusted users are root, the Exim user, any user listed in the
%trusted_users% configuration option, and any user whose current group or any
supplementary group is one of those listed in the %trusted_groups%
configuration option. Note that the Exim group is not automatically trusted.
+
cindex:[``From'' line]
cindex:[envelope sender]
Trusted users are always permitted to use the %-f% option or a leading ``From ''
line to specify the envelope sender of a message that is passed to Exim through
the local interface (see the %-bm% and %-f% options below). See the
%untrusted_set_sender% option for a way of permitting non-trusted users to
set envelope senders.
+
cindex:['From:' header line]
cindex:['Sender:' header line]
For a trusted user, there is never any check on the contents of the 'From:'
header line, and a 'Sender:' line is never added. Furthermore, any existing
'Sender:' line in incoming local (non-TCP/IP) messages is not removed.
+
Trusted users may also specify a host name, host address, interface address,
protocol name, ident value, and authentication data when submitting a message
locally. Thus, they are able to insert messages into Exim's queue locally that
have the characteristics of messages received from a remote host. Untrusted
users may in some circumstances use %-f%, but can never set the other values
that are available to trusted users.

- cindex:[user, admin definition of]
cindex:[admin user,definition of]
The admin users are root, the Exim user, and any user that is a member of the
Exim group or of any group listed in the %admin_groups% configuration option.
The current group does not have to be one of these groups.
+
Admin users are permitted to list the queue, and to carry out certain
operations on messages, for example, to force delivery failures. It is also
necessary to be an admin user in order to see the full information provided by
the Exim monitor, and full debugging output.
+
By default, the use of the %-M%, %-q%, %-R%, and %-S% options to cause Exim
to attempt delivery of messages on its queue is restricted to admin users.
However, this restriction can be relaxed by setting the %prod_requires_admin%
option false (that is, specifying %no_prod_requires_admin%).
+
Similarly, the use of the %-bp% option to list all the messages in the queue
is restricted to admin users unless %queue_list_requires_admin% is set
false.


*Warning*: If you configure your system so that admin users are able to
edit Exim's configuration file, you are giving those users an easy way of
getting root. There is further discussion of this issue at the start of chapter
<<CHAPconf>>.




Command line options
~~~~~~~~~~~~~~~~~~~~
The command options are described in alphabetical order below.

///
We insert a stylized DocBook comment here, to identify the start of the command
line options. This is for the benefit of the Perl script that automatically
creates a man page for the options.
///

++++
<!-- === Start of command line options === -->
++++


*{hh}*::
oindex:[{hh}]
cindex:[options, command line; terminating]
This is a pseudo-option whose only purpose is to terminate the options and
therefore to cause subsequent command line items to be treated as arguments
rather than options, even if they begin with hyphens.

*--help*::
oindex:[%{hh}help%]
This option causes Exim to output a few sentences stating what it is.
The same output is generated if the Exim binary is called with no options and
no arguments.

*-B*<'type'>::
oindex:[%-B%]
cindex:[8-bit characters]
cindex:[Sendmail compatibility,8-bit characters]
This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
clean; it ignores this option.

*-bd*::
oindex:[%-bd%]
cindex:[daemon]
cindex:[SMTP listener]
cindex:[queue runner]
This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
the %-bd% option is combined with the %-q%<'time'> option, to specify that
the daemon should also initiate periodic queue runs.
+
The %-bd% option can be used only by an admin user. If either of the %-d%
(debugging) or %-v% (verifying) options are set, the daemon does not
disconnect from the controlling terminal. When running this way, it can be
stopped by pressing ctrl-C.
+
By default, Exim listens for incoming connections to the standard SMTP port on
all the host's running interfaces. However, it is possible to listen on other
ports, on multiple ports, and only on specific interfaces. Chapter
<<CHAPinterfaces>> contains a description of the options that control this.
+
When a listening daemon
cindex:[daemon,process id (pid)]
cindex:[pid (process id),of daemon]
is started without the use of %-oX% (that is, without overriding the normal
configuration), it writes its process id to a file called _exim-daemon.pid_ in
Exim's spool directory. This location can be overridden by setting
PID_FILE_PATH in _Local/Makefile_. The file is written while Exim is still
running as root.
+
When %-oX% is used on the command line to start a listening daemon, the
process id is not written to the normal pid file path. However, %-oP% can be
used to specify a path on the command line if a pid file is required.
+
The SIGHUP signal
cindex:[SIGHUP]
can be used to cause the daemon to re-exec itself. This should be done whenever
Exim's configuration file, or any file that is incorporated into it by means of
the %.include% facility, is changed, and also whenever a new version of Exim is
installed. It is not necessary to do this when other files that are referenced
from the configuration (for example, alias files) are changed, because these
are reread each time they are used.

*-bdf*::
oindex:[%-bdf%]
This option has the same effect as %-bd% except that it never disconnects from
the controlling terminal, even when no debugging is specified.

*-be*::
oindex:[%-be%]
cindex:[testing,string expansion]
cindex:[expansion,testing]
Run Exim in expansion testing mode. Exim discards its root privilege, to
prevent ordinary users from using this mode to read otherwise inaccessible
files. If no arguments are given, Exim runs interactively, prompting for lines
of data.
+
If Exim was built with USE_READLINE=yes in _Local/Makefile_, it tries
to load the %libreadline% library dynamically whenever the %-be% option is
used without command line arguments. If successful, it uses the 'readline()'
function, which provides extensive line-editing facilities, for reading the
test data. A line history is supported.
+
Long expansion expressions can be split over several lines by using backslash
continuations. As in Exim's run time configuration, whitespace at the start of
continuation lines is ignored. Each argument or data line is passed through the
string expansion mechanism, and the result is output. Variable values from the
configuration file (for example, $qualify_domain$) are available, but no
message-specific values (such as $domain$) are set, because no message is
being processed.

*-bF*~<'filename'>::
oindex:[%-bF%]
cindex:[system filter,testing]
cindex:[testing,system filter]
This option is the same as %-bf% except that it assumes that the filter being
tested is a system filter. The additional commands that are available only in
system filters are recognized.

*-bf*~<'filename'>::
oindex:[%-bf%]
cindex:[filter,testing]
cindex:[testing,filter file]
cindex:[forward file,testing]
cindex:[testing,forward file]
cindex:[Sieve filter,testing]
This option runs Exim in user filter testing mode; the file is the filter file
to be tested, and a test message must be supplied on the standard input. If
there are no message-dependent tests in the filter, an empty file can be
supplied.
+
If you want to test a system filter file, use %-bF% instead of %-bf%. You can
use both %-bF% and %-bf% on the same command, in order to
test a system filter and a user filter in the same run. For example:

  exim -bF /system/filter -bf /user/filter </test/message
+
This is helpful when the system filter adds header lines or sets filter
variables that are used by the user filter.
+
If the test filter file does not begin with one of the special lines

  # Exim filter
  # Sieve filter
+
it is taken to be a normal _.forward_ file, and is tested for validity under
that interpretation. See sections <<SECTitenonfilred>> to <<SECTspecitredli>> for a
description of the possible contents of non-filter redirection lists.
+
The result of an Exim command that uses %-bf%, provided no errors are
detected, is a list of the actions that Exim would try to take if presented
with the message for real. More details of filter testing are given in the
separate document entitled 'Exim's interfaces to mail filtering'.
+
When testing a filter file,
cindex:[``From'' line]
cindex:[envelope sender]
cindex:[%-f% option,for filter testing]
the envelope sender can be set by the %-f% option,
or by a ``From '' line at the start of the test message. Various parameters that
would normally be taken from the envelope recipient address of the message can
be set by means of additional command line options (see the next four options).

*-bfd*~<'domain'>::
oindex:[%-bfd%]
This sets the domain of the recipient address when a filter file is being
tested by means of the %-bf% option. The default is the value of
$qualify_domain$.

*-bfl*~<'local~part'>::
oindex:[%-bfl%]
This sets the local part of the recipient address when a filter file is being
tested by means of the %-bf% option. The default is the username of the
process that calls Exim. A local part should be specified with any prefix or
suffix stripped, because that is how it appears to the filter when a message is
actually being delivered.

*-bfp*~<'prefix'>::
oindex:[%-bfp%]
This sets the prefix of the local part of the recipient address when a filter
file is being tested by means of the %-bf% option. The default is an empty
prefix.

*-bfs*~<'suffix'>::
oindex:[%-bfs%]
This sets the suffix of the local part of the recipient address when a filter
file is being tested by means of the %-bf% option. The default is an empty
suffix.

*-bh*~<'IP~address'>::
oindex:[%-bh%]
cindex:[testing,incoming SMTP]
cindex:[SMTP,testing incoming]
cindex:[testing,relay control]
cindex:[relaying,testing configuration]
cindex:[policy control,testing]
cindex:[debugging,%-bh% option]
This option runs a fake SMTP session as if from the given IP address, using the
standard input and output. The IP address may include a port number at the end,
after a full stop. For example:

  exim -bh 10.9.8.7.1234
  exim -bh fe80::a00:20ff:fe86:a061.5678
+
When an IPv6 address is given, it is converted into canonical form. In the case
of the second example above, the value of $sender_host_address$ after
conversion to the canonical form is `fe80:0000:0000:0a00:20ff:fe86:a061.5678`.
+
Comments as to what is going on are written to the standard error file. These
include lines beginning with ``LOG'' for anything that would have been logged.
This facility is provided for testing configuration options for incoming
messages, to make sure they implement the required policy. For example, you can
test your relay controls using %-bh%.
+
*Warning 1*:
cindex:[RFC 1413]
You cannot test features of the configuration that rely on
ident (RFC 1413) callouts. These cannot be done when testing using
%-bh% because there is no incoming SMTP connection.
+
*Warning 2*: Address verification callouts (see section <<SECTcallver>>) are
also skipped when testing using %-bh%. If you want these callouts to occur,
use %-bhc% instead.
+
Messages supplied during the testing session are discarded, and nothing is
written to any of the real log files. There may be pauses when DNS (and other)
lookups are taking place, and of course these may time out. The %-oMi% option
can be used to specify a specific IP interface and port if this is important.
+
The 'exim_checkaccess' utility is a ``packaged'' version of %-bh% whose
output just states whether a given recipient address from a given host is
acceptable or not. See section <<SECTcheckaccess>>.

*-bhc*~<'IP~address'>::
oindex:[%-bhc%]
This option operates in the same way as %-bh%, except that address
verification callouts are performed if required. This includes consulting and
updating the callout cache database.

*-bi*::
oindex:[%-bi%]
cindex:[alias file,building]
cindex:[building alias file]
cindex:[Sendmail compatibility,%-bi% option]
Sendmail interprets the %-bi% option as a request to rebuild its alias file.
Exim does not have the concept of a single alias file, and so it cannot mimic
this behaviour. However, calls to _/usr/lib/sendmail_ with the %-bi% option
tend to appear in various scripts such as NIS make files, so the option must be
recognized.
+
If %-bi% is encountered, the command specified by the %bi_command%
configuration option is run, under the uid and gid of the caller of Exim. If
the %-oA% option is used, its value is passed to the command as an argument.
The command set by %bi_command% may not contain arguments. The command can use
the 'exim_dbmbuild' utility, or some other means, to rebuild alias files if
this is required. If the %bi_command% option is not set, calling Exim with
%-bi% is a no-op.

*-bm*::
oindex:[%-bm%]
cindex:[local message reception]
This option runs an Exim receiving process that accepts an incoming,
locally-generated message on the current input. The recipients are given as the
command arguments (except when %-t% is also present -- see below). Each
argument can be a comma-separated list of RFC 2822 addresses. This is the
default option for selecting the overall action of an Exim call; it is assumed
if no other conflicting option is present.
+
If any addresses in the message are unqualified (have no domain), they are
qualified by the values of the %qualify_domain% or %qualify_recipient%
options, as appropriate. The %-bnq% option (see below) provides a way of
suppressing this for special cases.
+
Policy checks on the contents of local messages can be enforced by means of
the non-SMTP ACL. See chapter <<CHAPACL>> for details.
+
The return code
cindex:[return code,for %-bm%]
is zero if the message is successfully accepted. Otherwise, the
action is controlled by the %-oe'x'% option setting -- see below.
+
The format
cindex:[message,format]
cindex:[format,message]
cindex:[``From'' line]
cindex:[UUCP,``From'' line]
cindex:[Sendmail compatibility,``From'' line]
of the message must be as defined in RFC 2822, except that, for
compatibility with Sendmail and Smail, a line in one of the forms

  From sender Fri Jan  5 12:55 GMT 1997
  From sender Fri, 5 Jan 97 12:55:01
+
(with the weekday optional, and possibly with additional text after the date)
is permitted to appear at the start of the message. There appears to be no
authoritative specification of the format of this line. Exim recognizes it by
matching against the regular expression defined by the %uucp_from_pattern%
option, which can be changed if necessary.
+
The
cindex:[%-f% option,overriding ``From'' line]
specified sender is treated as if it were given as the argument to the
%-f% option, but if a %-f% option is also present, its argument is used in
preference to the address taken from the message. The caller of Exim must be a
trusted user for the sender of a message to be set in this way.

*-bnq*::
oindex:[%-bnq%]
cindex:[address qualification, suppressing]
By default, Exim automatically qualifies unqualified addresses (those
without domains) that appear in messages that are submitted locally (that
is, not over TCP/IP). This qualification applies both to addresses in
envelopes, and addresses in header lines. Sender addresses are qualified using
%qualify_domain%, and recipient addresses using %qualify_recipient% (which
defaults to the value of %qualify_domain%).
+
Sometimes, qualification is not wanted. For example, if %-bS% (batch SMTP) is
being used to re-submit messages that originally came from remote hosts after
content scanning, you probably do not want to qualify unqualified addresses in
header lines. (Such lines will be present only if you have not enabled a header
syntax check in the appropriate ACL.)
+
The %-bnq% option suppresses all qualification of unqualified addresses in
messages that originate on the local host. When this is used, unqualified
addresses in the envelope provoke errors (causing message rejection) and
unqualified addresses in header lines are left alone.


*-bP*::
oindex:[%-bP%]
cindex:[configuration options, extracting]
cindex:[options,configuration -- extracting]
If this option is given with no arguments, it causes the values of all Exim's
main configuration options to be written to the standard output. The values
of one or more specific options can be requested by giving their names as
arguments, for example:

  exim -bP qualify_domain hold_domains
+
However, any option setting that is preceded by the word ``hide'' in the
configuration file is not shown in full, except to an admin user. For other
users, the output is as in this example:

  mysql_servers = <value not displayable>
+
If %configure_file% is given as an argument, the name of the run time
configuration file is output.
If a list of configuration files was supplied, the value that is output here
is the name of the file that was actually used.
+
cindex:[daemon,process id (pid)]
cindex:[pid (process id),of daemon]
If %log_file_path% or %pid_file_path% are given, the names of the directories
where log files and daemon pid files are written are output, respectively. If
these values are unset, log files are written in a sub-directory of the spool
directory called %log%, and the pid file is written directly into the spool
directory.
+
If %-bP% is followed by a name preceded by `+`, for example,

  exim -bP +local_domains
+
it searches for a matching named list of any type (domain, host, address, or
local part) and outputs what it finds.
+
If
cindex:[options,router -- extracting]
cindex:[options,transport -- extracting]
one of the words %router%, %transport%, or %authenticator% is given,
followed by the name of an appropriate driver instance, the option settings for
that driver are output. For example:

  exim -bP transport local_delivery
+
The generic driver options are output first, followed by the driver's private
options. A list of the names of drivers of a particular type can be obtained by
using one of the words %router_list%, %transport_list%, or
%authenticator_list%, and a complete list of all drivers with their option
settings can be obtained by using %routers%, %transports%, or %authenticators%.


*-bp*::
oindex:[%-bp%]
cindex:[queue,listing messages on]
cindex:[listing,messages on the queue]
This option requests a listing of the contents of the mail queue on the
standard output. If the %-bp% option is followed by a list of message ids,
just those messages are listed. By default, this option can be used only by an
admin user. However, the %queue_list_requires_admin% option can be set false
to allow any user to see the queue.
+
Each message on the queue is displayed as in the following example:

  25m  2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
            red.king@looking-glass.fict.example
            <other addresses>
+
The
cindex:[message,size in queue listing]
cindex:[size,of message]
first line contains the length of time the message has been on the queue
(in this case 25 minutes), the size of the message (2.9K), the unique local
identifier for the message, and the message sender, as contained in the
envelope. For bounce messages, the sender address is empty, and appears as
``<>''. If the message was submitted locally by an untrusted user who overrode
the default sender address, the user's login name is shown in parentheses
before the sender address.
+
If
cindex:[frozen messages,in queue listing]
the message is frozen (attempts to deliver it are suspended) then the text
``\*\*\* frozen \*\*\*'' is displayed at the end of this line.
+
The recipients of the message (taken from the envelope, not the headers) are
displayed on subsequent lines. Those addresses to which the message has already
been delivered are marked with the letter D. If an original address gets
expanded into several addresses via an alias or forward file, the original is
displayed with a D only when deliveries for all of its child addresses are
complete.


*-bpa*::
oindex:[%-bpa%]
This option operates like %-bp%, but in addition it shows delivered addresses
that were generated from the original top level address(es) in each message by
alias or forwarding operations. These addresses are flagged with ``+D'' instead
of just ``D''.


*-bpc*::
oindex:[%-bpc%]
cindex:[queue,count of messages on]
This option counts the number of messages on the queue, and writes the total
to the standard output. It is restricted to admin users, unless
%queue_list_requires_admin% is set false.


*-bpr*::
oindex:[%-bpr%]
This option operates like %-bp%, but the output is not sorted into
chronological order of message arrival. This can speed it up when there are
lots of messages on the queue, and is particularly useful if the output is
going to be post-processed in a way that doesn't need the sorting.

*-bpra*::
oindex:[%-bpra%]
This option is a combination of %-bpr% and %-bpa%.

*-bpru*::
oindex:[%-bpru%]
This option is a combination of %-bpr% and %-bpu%.


*-bpu*::
oindex:[%-bpu%]
This option operates like %-bp% but shows only undelivered top-level addresses
for each message displayed. Addresses generated by aliasing or forwarding are
not shown, unless the message was deferred after processing by a router with
the %one_time% option set.


*-brt*::
oindex:[%-brt%]
cindex:[testing,retry configuration]
cindex:[retry,configuration testing]
This option is for testing retry rules, and it must be followed by up to three
arguments. It causes Exim to look for a retry rule that matches the values
and to write it to the standard output. For example:

  exim -brt bach.comp.mus.example
  Retry rule: *.comp.mus.example  F,2h,15m; F,4d,30m;
+
See chapter <<CHAPretry>> for a description of Exim's retry rules. The first
argument, which is required, can be a complete address in the form
'local_part@domain', or it can be just a domain name. The second argument is
an optional second domain name; if no retry rule is found for the first
argument, the second is tried. This ties in with Exim's behaviour when looking
for retry rules for remote hosts -- if no rule is found that matches the host,
one that matches the mail domain is sought. The final argument is the name of a
specific delivery error, as used in setting up retry rules, for example
``quota_3d''.

*-brw*::
oindex:[%-brw%]
cindex:[testing,rewriting]
cindex:[rewriting,testing]
This option is for testing address rewriting rules, and it must be followed by
a single argument, consisting of either a local part without a domain, or a
complete address with a fully qualified domain. Exim outputs how this address
would be rewritten for each possible place it might appear. See chapter
<<CHAPrewrite>> for further details.

*-bS*::
oindex:[%-bS%]
cindex:[SMTP,batched incoming]
cindex:[batched SMTP input]
This option is used for batched SMTP input, which is an alternative interface
for non-interactive local message submission. A number of messages can be
submitted in a single run. However, despite its name, this is not really SMTP
input. Exim reads each message's envelope from SMTP commands on the standard
input, but generates no responses. If the caller is trusted, or
%untrusted_set_sender% is set, the senders in the SMTP MAIL commands are
believed; otherwise the sender is always the caller of Exim.
+
The message itself is read from the standard input, in SMTP format (leading
dots doubled), terminated by a line containing just a single dot. An error is
provoked if the terminating dot is missing. A further message may then follow.
+
As for other local message submissions, the contents of incoming batch SMTP
messages can be checked using the non-SMTP ACL (see chapter <<CHAPACL>>).
Unqualified addresses are automatically qualified using %qualify_domain% and
%qualify_recipient%, as appropriate, unless the %-bnq% option is used.
+
Some other SMTP commands are recognized in the input. HELO and EHLO act
as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
QUIT quits, ignoring the rest of the standard input.
+
cindex:[return code,for %-bS%]
If any error is encountered, reports are written to the standard output and
error streams, and Exim gives up immediately. The return code is 0 if no error
was detected; it is 1 if one or more messages were accepted before the error
was detected; otherwise it is 2.
+
More details of input using batched SMTP are given in section
<<SECTincomingbatchedSMTP>>.

*-bs*::
oindex:[%-bs%]
cindex:[SMTP,local input]
cindex:[local SMTP input]
This option causes Exim to accept one or more messages by reading SMTP commands
on the standard input, and producing SMTP replies on the standard output. SMTP
policy controls, as defined in ACLs (see chapter <<CHAPACL>>) are applied.
Some user agents use this interface as a way of passing locally-generated
messages to the MTA.
+
In
cindex:[sender,source of]
this usage, if the caller of Exim is trusted, or %untrusted_set_sender% is
set, the senders of messages are taken from the SMTP MAIL commands.
Otherwise the content of these commands is ignored and the sender is set up as
the calling user. Unqualified addresses are automatically qualified using
%qualify_domain% and %qualify_recipient%, as appropriate, unless the %-bnq%
option is used.
+
cindex:[inetd]
The
%-bs% option is also used to run Exim from 'inetd', as an alternative to using
a listening daemon. Exim can distinguish the two cases by checking whether the
standard input is a TCP/IP socket. When Exim is called from 'inetd', the source
of the mail is assumed to be remote, and the comments above concerning senders
and qualification do not apply. In this situation, Exim behaves in exactly the
same way as it does when receiving a message via the listening daemon.

*-bt*::
oindex:[%-bt%]
cindex:[testing,addresses]
cindex:[address,testing]
This option runs Exim in address testing mode, in which each argument is taken
as an address to be tested for deliverability. The results are written to the
standard output. If a test fails, and the caller is not an admin user, no
details of the failure are output, because these might contain sensitive
information such as usernames and passwords for database lookups.
+
If no arguments are given, Exim runs in an interactive manner, prompting with a
right angle bracket for addresses to be tested.
+
Unlike the %-be% test option, you cannot arrange for Exim to use the
'readline()' function, because it is running as 'root' and there are
security issues.
+
Each address is handled as if it were the recipient address of a message
(compare the %-bv% option). It is passed to the routers and the result is
written to the standard output. However, any router that has
%no_address_test% set is bypassed. This can make %-bt% easier to use for
genuine routing tests if your first router passes everything to a scanner
program.
+
The
cindex:[return code,for %-bt%]
return code is 2 if any address failed outright; it is 1 if no address
failed outright but at least one could not be resolved for some reason. Return
code 0 is given only when all addresses succeed.
+
*Warning*: %-bt% can only do relatively simple testing. If any of the
routers in the configuration makes any tests on the sender address of a
message,
cindex:[%-f% option,for address testing]
you can use the %-f% option to set an appropriate sender when running
%-bt% tests. Without it, the sender is assumed to be the calling user at the
default qualifying domain. However, if you have set up (for example) routers
whose behaviour depends on the contents of an incoming message, you cannot test
those conditions using %-bt%. The %-N% option provides a possible way of
doing such tests.

*-bV*::
oindex:[%-bV%]
cindex:[version number of Exim, verifying]
This option causes Exim to write the current version number, compilation
number, and compilation date of the 'exim' binary to the standard output.
It also lists the DBM library this is being used, the optional modules (such as
specific lookup types), the drivers that are included in the binary, and the
name of the run time configuration file that is in use.
+
As part of its operation, %-bV% causes Exim to read and syntax check its
configuration file. However, this is a static check only. It cannot check
values that are to be expanded. For example, although a misspelt ACL verb is
detected, an error in the verb's arguments is not. You cannot rely on %-bV%
alone to discover (for example) all the typos in the configuration; some
realistic testing is needed. The %-bh% and %-N% options provide more dynamic
testing facilities.

*-bv*::
oindex:[%-bv%]
cindex:[verifying address, using %-bv%]
cindex:[address,verification]
This option runs Exim in address verification mode, in which each argument is
taken as an address to be verified. During normal operation, verification
happens mostly as a consequence processing a %verify% condition in an ACL (see
chapter <<CHAPACL>>). If you want to test an entire ACL, see the %-bh% option.
+
If verification fails, and the caller is not an admin user, no details of the
failure are output, because these might contain sensitive information such as
usernames and passwords for database lookups.
+
If no arguments are given, Exim runs in an interactive manner, prompting with a
right angle bracket for addresses to be verified.
+
Unlike the %-be% test option, you cannot arrange for Exim to use the
'readline()' function, because it is running as 'exim' and there are
security issues.
+
Verification differs from address testing (the %-bt% option) in that routers
that have %no_verify% set are skipped, and if the address is accepted by a
router that has %fail_verify% set, verification fails. The address is verified
as a recipient if %-bv% is used; to test verification for a sender address,
%-bvs% should be used.
+
If the %-v% option is not set, the output consists of a single line for each
address, stating whether it was verified or not, and giving a reason in the
latter case. Otherwise, more details are given of how the address has been
handled, and in the case of address redirection, all the generated addresses
are also considered. Without %-v%, generating more than one address by
redirection causes verification to end sucessfully.
+
The
cindex:[return code,for %-bv%]
return code is 2 if any address failed outright; it is 1 if no address
failed outright but at least one could not be resolved for some reason. Return
code 0 is given only when all addresses succeed.
+
If any of the routers in the configuration makes any tests on the sender
address of a message, you should use the %-f% option to set an appropriate
sender when running %-bv% tests. Without it, the sender is assumed to be the
calling user at the default qualifying domain.

*-bvs*::
oindex:[%-bvs%]
This option acts like %-bv%, but verifies the address as a sender rather
than a recipient address. This affects any rewriting and qualification that
might happen.

*-C*~<'filelist'>::
oindex:[%-C%]
cindex:[configuration file,alternate]
cindex:[CONFIGURE_FILE]
cindex:[alternate configuration file]
This option causes Exim to find the run time configuration file from the given
list instead of from the list specified by the CONFIGURE_FILE
compile-time setting. Usually, the list will consist of just a single file
name, but it can be a colon-separated list of names. In this case, the first
file that exists is used. Failure to open an existing file stops Exim from
proceeding any further along the list, and an error is generated.
+
When this option is used by a caller other than root or the Exim user, and the
list is different from the compiled-in list, Exim gives up its root privilege
immediately, and runs with the real and effective uid and gid set to those of
the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in
_Local/Makefile_, root privilege is retained for %-C% only if the caller of
Exim is root.
+
That is, the Exim user is no longer privileged in this regard. This build-time
option is not set by default in the Exim source distribution tarbundle.
However, if you are using a ``packaged'' version of Exim (source or binary), the
packagers might have enabled it.
+
Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a
configuration using %-C% right through message reception and delivery, even if
the caller is root. The reception works, but by that time, Exim is running as
the Exim user, so when it re-execs to regain privilege for the delivery, the
use of %-C% causes privilege to be lost. However, root can test reception and
delivery using two separate commands (one to put a message on the queue, using
%-odq%, and another to do the delivery, using %-M%).
+
If ALT_CONFIG_PREFIX is defined _in Local/Makefile_, it specifies a
prefix string with which any file named in a %-C% command line option
must start. In addition, the file name must not contain the sequence `/../`.
However, if the value of the %-C% option is identical to the value of
CONFIGURE_FILE in _Local/Makefile_, Exim ignores %-C% and proceeds as
usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
unset, any file name can be used with %-C%.
+
ALT_CONFIG_PREFIX can be used to confine alternative configuration files
to a directory to which only root has access. This prevents someone who has
broken into the Exim account from running a privileged Exim with an arbitrary
configuration file.
+
The %-C% facility is useful for ensuring that configuration files are
syntactically correct, but cannot be used for test deliveries, unless the
caller is privileged, or unless it is an exotic configuration that does not
require privilege. No check is made on the owner or group of the files
specified by this option.

*-D*<'macro'>=<'value'>::
oindex:[%-D%]
cindex:[macro,setting on command line]
This option can be used to override macro definitions in the configuration file
(see section <<SECTmacrodefs>>). However, like %-C%, if it is used by an
unprivileged caller, it causes Exim to give up its root privilege.
If DISABLE_D_OPTION is defined in _Local/Makefile_, the use of %-D% is
completely disabled, and its use causes an immediate error exit.
+
The entire option (including equals sign if present) must all be within one
command line item. %-D% can be used to set the value of a macro to the empty
string, in which case the equals sign is optional. These two commands are
synonymous:

  exim -DABC  ...
  exim -DABC= ...
+
To include spaces in a macro definition item, quotes must be used. If you use
quotes, spaces are permitted around the macro name and the equals sign. For
example:

  exim '-D ABC = something' ...
+
%-D% may be repeated up to 10 times on a command line.

*-d*<'debug~options'>::
oindex:[%-d%]
cindex:[debugging,list of selectors]
cindex:[debugging,%-d% option]
This option causes debugging information to be written to the standard
error stream. It is restricted to admin users because debugging output may show
database queries that contain password information. Also, the details of users'
filter files should be protected. When %-d% is used, %-v% is assumed. If
%-d% is given on its own, a lot of standard debugging data is output. This can
be reduced, or increased to include some more rarely needed information, by
following %-d% with a string made up of names preceded by plus or minus
characters. These add or remove sets of debugging data, respectively. For
example, %-d+filter% adds filter debugging, whereas %-d-all+filter% selects
only filter debugging. The available debugging categories are:
+
&&&
`acl            ` ACL interpretation
`auth           ` authenticators
`deliver        ` general delivery logic
`dns            ` DNS lookups (see also resolver)
`dnsbl          ` DNS black list (aka RBL) code
`exec           ` arguments for ^^execv()^^ calls
`expand         ` detailed debugging for string expansions
`filter         ` filter handling
`hints_lookup   ` hints data lookups
`host_lookup    ` all types of name-to-IP address handling
`ident          ` ident lookup
`interface      ` lists of local interfaces
`lists          ` matching things in lists
`load           ` system load checks
`local_scan     ` can be used by ^^local_scan()^^ (see chapter <<CHAPlocalscan>>)
`lookup         ` general lookup code and all lookups
`memory         ` memory handling
`pid            ` add pid to debug output lines
`process_info   ` setting info for the process log
`queue_run      ` queue runs
`receive        ` general message reception logic
`resolver       ` turn on the DNS resolver's debugging output
`retry          ` retry handling
`rewrite        ` address rewriting
`route          ` address routing
`timestamp      ` add timestamp to debug output lines
`tls            ` TLS logic
`transport      ` transports
`uid            ` changes of uid/gid and looking up uid/gid
`verify         ` address verification logic
`all            ` all of the above, and also %-v%
&&&
+
The
cindex:[resolver, debugging output]
cindex:[DNS resolver, debugging output]
`resolver` option produces output only if the DNS resolver was compiled
with DEBUG enabled. This is not the case in some operating systems. Also,
unfortunately, debugging output from the DNS resolver is written to stdout
rather than stderr.
+
The default (%-d% with no argument) omits `expand`, `filter`,
`interface`, `load`, `memory`, `pid`, `resolver`, and `timestamp`.
However, the `pid` selector is forced when debugging is turned on for a
daemon, which then passes it on to any re-executed Exims. Exim also
automatically adds the pid to debug lines when several remote deliveries are
run in parallel.
+
The `timestamp` selector causes the current time to be inserted at the start
of all debug output lines. This can be useful when trying to track down delays
in processing.
+
If the %debug_print% option is set in any driver, it produces output whenever
any debugging is selected, or if %-v% is used.

*-dd*<'debug~options'>::
oindex:[%-dd%]
This option behaves exactly like %-d% except when used on a command that
starts a daemon process. In that case, debugging is turned off for the
subprocesses that the daemon creates. Thus, it is useful for monitoring the
behaviour of the daemon without creating as much output as full debugging does.

*-dropcr*::
oindex:[%-dropcr%]
This is an obsolete option that is now a no-op. It used to affect the way Exim
handled CR and LF characters in incoming messages. What happens now is
described in section <<SECTlineendings>>.

*-E*::
oindex:[%-E%]
cindex:[bounce message,generating]
This option specifies that an incoming message is a locally-generated delivery
failure report. It is used internally by Exim when handling delivery failures
and is not intended for external use. Its only effect is to stop Exim
generating certain messages to the postmaster, as otherwise message cascades
could occur in some situations. As part of the same option, a message id may
follow the characters %-E%. If it does, the log entry for the receipt of the
new message contains the id, following ``R='', as a cross-reference.

*-e*'x'::
oindex:[%-e'x'%]
There are a number of Sendmail options starting with %-oe% which seem to be
called by various programs without the leading %o% in the option. For example,
the %vacation% program uses %-eq%. Exim treats all options of the form
%-e'x'% as synonymous with the corresponding %-oe'x'% options.

*-F*~<'string'>::
oindex:[%-F%]
cindex:[sender,name]
cindex:[name,of sender]
This option sets the sender's full name for use when a locally-generated
message is being accepted. In the absence of this option, the user's 'gecos'
entry from the password data is used. As users are generally permitted to alter
their 'gecos' entries, no security considerations are involved. White space
between %-F% and the <'string'> is optional.

*-f*~<'address'>::
oindex:[%-f%]
cindex:[sender,address]
cindex:[address,sender]
cindex:[trusted user]
cindex:[envelope sender]
cindex:[user,trusted]
This option sets the address of the envelope sender of a locally-generated
message (also known as the return path). The option can normally be used only
by a trusted user, but %untrusted_set_sender% can be set to allow untrusted
users to use it.
+
Processes running as root or the Exim user are always trusted. Other
trusted users are defined by the %trusted_users% or %trusted_groups% options.
In the absence of %-f%, or if the caller is not trusted, the sender of a local
message is set to the caller's login name at the default qualify domain.
+
There is one exception to the restriction on the use of %-f%: an empty sender
can be specified by any user, trusted or not, to create a message that can
never provoke a bounce. An empty sender can be specified either as an empty
string, or as a pair of angle brackets with nothing between them, as in these
examples of shell commands:

  exim -f '<>' user@domain
  exim -f "" user@domain
+
In addition, the use of %-f% is not restricted when testing a filter file with
%-bf% or when testing or verifying addresses using the %-bt% or %-bv%
options.
+
Allowing untrusted users to change the sender address does not of itself make
it possible to send anonymous mail. Exim still checks that the 'From:' header
refers to the local user, and if it does not, it adds a 'Sender:' header,
though this can be overridden by setting %no_local_from_check%.
+
White
cindex:[``From'' line]
space between %-f% and the <'address'> is optional (that is, they can be given
as two arguments or one combined argument). The sender of a locally-generated
message can also be set (when permitted) by an initial ``From '' line in the
message -- see the description of %-bm% above -- but if %-f% is also present,
it overrides ``From''.

*-G*::
oindex:[%-G%]
cindex:[Sendmail compatibility,%-G% option ignored]
This is a Sendmail option which is ignored by Exim.

*-h*~<'number'>::
oindex:[%-h%]
cindex:[Sendmail compatibility,%-h% option ignored]
This option is accepted for compatibility with Sendmail, but has no effect. (In
Sendmail it overrides the ``hop count'' obtained by counting 'Received:'
headers.)

*-i*::
oindex:[%-i%]
cindex:[Solaris,'mail' command]
cindex:[dot in incoming, non-SMTP message]
This option, which has the same effect as %-oi%, specifies that a dot on a line
by itself should not terminate an incoming, non-SMTP message. I can find no
documentation for this option in Solaris 2.4 Sendmail, but the 'mailx' command
in Solaris 2.4 uses it. See also %-ti%.

*-M*~<'message~id'>~<'message~id'>~...::
oindex:[%-M%]
cindex:[forcing delivery]
cindex:[delivery,forcing attempt]
cindex:[frozen messages,forcing delivery]
This option requests Exim to run a delivery attempt on each message in turn. If
any of the messages are frozen, they are automatically thawed before the
delivery attempt. The settings of %queue_domains%, %queue_smtp_domains%, and
%hold_domains% are ignored.
+
Retry
cindex:[hints database,overriding retry hints]
hints for any of the addresses are overridden -- Exim tries to deliver even if
the normal retry time has not yet been reached. This option requires the caller
to be an admin user. However, there is an option called %prod_requires_admin%
which can be set false to relax this restriction (and also the same requirement
for the %-q%, %-R%, and %-S% options).

*-Mar*~<'message~id'>~<'address'>~<'address'>~...::
oindex:[%-Mar%]
cindex:[message,adding recipients]
cindex:[recipient,adding]
This option requests Exim to add the addresses to the list of recipients of the
message (``ar'' for ``add recipients''). The first argument must be a message id,
and the remaining ones must be email addresses. However, if the message is
active (in the middle of a delivery attempt), it is not altered. This option
can be used only by an admin user.

*-MC*~<'transport'>~<'hostname'>~<'sequence~number'>~<'message~id'>::
oindex:[%-MC%]
cindex:[SMTP,passed connection]
cindex:[SMTP,multiple deliveries]
cindex:[multiple SMTP deliveries]
This option is not intended for use by external callers. It is used internally
by Exim to invoke another instance of itself to deliver a waiting message using
an existing SMTP connection, which is passed as the standard input. Details are
given in chapter <<CHAPSMTP>>. This must be the final option, and the caller must
be root or the Exim user in order to use it.

*-MCA*::
oindex:[%-MCA%]
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the %-MC% option. It signifies that the connection
to the remote host has been authenticated.

*-MCP*::
oindex:[%-MCP%]
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the %-MC% option. It signifies that the server to
which Exim is connected supports pipelining.

*-MCQ*~<'process~id'>~<'pipe~fd'>::
oindex:[%-MCQ%]
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the %-MC% option when the original delivery was
started by a queue runner. It passes on the process id of the queue runner,
together with the file descriptor number of an open pipe. Closure of the pipe
signals the final completion of the sequence of processes that are passing
messages through the same SMTP connection.

*-MCS*::
oindex:[%-MCS%]
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the %-MC% option, and passes on the fact that the
SMTP SIZE option should be used on messages delivered down the existing
connection.

*-MCT*::
oindex:[%-MCT%]
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the %-MC% option, and passes on the fact that the
host to which Exim is connected supports TLS encryption.

*-Mc*~<'message~id'>~<'message~id'>~...::
oindex:[%-Mc%]
cindex:[hints database,not overridden by %-Mc%]
cindex:[delivery,manually started -- not forced]
This option requests Exim to run a delivery attempt on each message in turn,
but unlike the %-M% option, it does check for retry hints, and respects any
that are found. This option is not very useful to external callers. It is
provided mainly for internal use by Exim when it needs to re-invoke itself in
order to regain root privilege for a delivery (see chapter <<CHAPsecurity>>).
However, %-Mc% can be useful when testing, in order to run a delivery that
respects retry times and other options such as %hold_domains% that are
overridden when %-M% is used. Such a delivery does not count as a queue run.
If you want to run a specific delivery as if in a queue run, you should use
%-q% with a message id argument. A distinction between queue run deliveries
and other deliveries is made in one or two places.

*-Mes*~<'message~id'>~<'address'>::
oindex:[%-Mes%]
cindex:[message,changing sender]
cindex:[sender,changing]
This option requests Exim to change the sender address in the message to the
given address, which must be a fully qualified address or ``<>'' (``es'' for ``edit
sender''). There must be exactly two arguments. The first argument must be a
message id, and the second one an email address. However, if the message is
active (in the middle of a delivery attempt), its status is not altered. This
option can be used only by an admin user.

*-Mf*~<'message~id'>~<'message~id'>~...::
oindex:[%-Mf%]
cindex:[freezing messages]
cindex:[message,manually freezing]
This option requests Exim to mark each listed message as ``frozen''. This
prevents any delivery attempts taking place until the message is ``thawed'',
either manually or as a result of the %auto_thaw% configuration option.
However, if any of the messages are active (in the middle of a delivery
attempt), their status is not altered. This option can be used only by an admin
user.

*-Mg*~<'message~id'>~<'message~id'>~...::
oindex:[%-Mg%]
cindex:[giving up on messages]
cindex:[message,abandoning delivery attempts]
cindex:[delivery,abandoning further attempts]
This option requests Exim to give up trying to deliver the listed messages,
including any that are frozen. However, if any of the messages are active,
their status is not altered. For non-bounce messages, a delivery error message
is sent to the sender, containing the text ``cancelled by administrator''.
Bounce messages are just discarded. This option can be used only by an admin
user.

*-Mmad*~<'message~id'>~<'message~id'>~...::
oindex:[%-Mmad%]
cindex:[delivery,cancelling all]
This option requests Exim to mark all the recipient addresses in the messages
as already delivered (``mad'' for ``mark all delivered''). However, if any
message is active (in the middle of a delivery attempt), its status is not
altered. This option can be used only by an admin user.

*-Mmd*~<'message~id'>~<'address'>~<'address'>~...::
oindex:[%-Mmd%]
cindex:[delivery,cancelling by address]
cindex:[recipient,removing]
cindex:[removing recipients]
This option requests Exim to mark the given addresses as already delivered
(``md'' for ``mark delivered''). The first argument must be a message id, and
the remaining ones must be email addresses. These are matched to recipient
addresses in the message in a case-sensitive manner. If the message is active
(in the middle of a delivery attempt), its status is not altered. This option
can be used only by an admin user.

*-Mrm*~<'message~id'>~<'message~id'>~...::
oindex:[%-Mrm%]
cindex:[removing messages]
cindex:[abandoning mail]
cindex:[message,manually discarding]
This option requests Exim to remove the given messages from the queue. No
bounce messages are sent; each message is simply forgotten. However, if any of
the messages are active, their status is not altered. This option can be used
only by an admin user or by the user who originally caused the message to be
placed on the queue.

*-Mt*~<'message~id'>~<'message~id'>~...::
oindex:[%-Mt%]
cindex:[thawing messages]
cindex:[unfreezing messages]
cindex:[frozen messages,thawing]
cindex:[message,thawing frozen]
This option requests Exim to ``thaw'' any of the listed messages that are
``frozen'', so that delivery attempts can resume. However, if any of the messages
are active, their status is not altered. This option can be used only by an
admin user.

*-Mvb*~<'message~id'>::
oindex:[%-Mvb%]
cindex:[listing,message body]
cindex:[message,listing body of]
This option causes the contents of the message body (-D) spool file to be
written to the standard output. This option can be used only by an admin user.

*-Mvh*~<'message~id'>::
oindex:[%-Mvh%]
cindex:[listing,message headers]
cindex:[header lines,listing]
cindex:[message,listing header lines]
This option causes the contents of the message headers (-H) spool file to be
written to the standard output. This option can be used only by an admin user.

*-Mvl*~<'message~id'>::
oindex:[%-Mvl%]
cindex:[listing,message log]
cindex:[message,listing message log]
This option causes the contents of the message log spool file to be written to
the standard output. This option can be used only by an admin user.

*-m*::
oindex:[%-m%]
This is apparently a synonym for %-om% that is accepted by Sendmail, so Exim
treats it that way too.

*-N*::
oindex:[%-N%]
cindex:[debugging,%-N% option]
cindex:[debugging,suppressing delivery]
This is a debugging option that inhibits delivery of a message at the transport
level. It implies %-v%. Exim goes through many of the motions of delivery --
it just doesn't actually transport the message, but instead behaves as if it
had successfully done so. However, it does not make any updates to the retry
database, and the log entries for deliveries are flagged with ``\*>'' rather
than ``=>''.
+
Because %-N% discards any message to which it applies, only root or the Exim
user are allowed to use it with %-bd%, %-q%, %-R% or %-M%. In other words,
an ordinary user can use it only when supplying an incoming message to which it
will apply. Although transportation never fails when %-N% is set, an address
may be deferred because of a configuration problem on a transport, or a routing
problem. Once %-N% has been used for a delivery attempt, it sticks to the
message, and applies to any subsequent delivery attempts that may happen for
that message.

*-n*::
oindex:[%-n%]
cindex:[Sendmail compatibility,%-n% option ignored]
This option is interpreted by Sendmail to mean ``no aliasing''. It is ignored by
Exim.

*-O*~<'data'>::
oindex:[%-O%]
This option is interpreted by Sendmail to mean `set option`. It is ignored by
Exim.

*-oA*~<'file~name'>::
oindex:[%-oA%]
cindex:[Sendmail compatibility,%-oA% option]
This option is used by Sendmail in conjunction with %-bi% to specify an
alternative alias file name. Exim handles %-bi% differently; see the
description above.

*-oB*~<'n'>::
oindex:[%-oB%]
cindex:[SMTP,passed connection]
cindex:[SMTP,multiple deliveries]
cindex:[multiple SMTP deliveries]
This is a debugging option which limits the maximum number of messages that can
be delivered down one SMTP connection, overriding the value set in any ^smtp^
transport. If <'n'> is omitted, the limit is set to 1.

*-odb*::
oindex:[%-odb%]
cindex:[background delivery]
cindex:[delivery,in the background]
This option applies to all modes in which Exim accepts incoming messages,
including the listening daemon. It requests ``background'' delivery of such
messages, which means that the accepting process automatically starts a
delivery process for each message received, but does not wait for the delivery
processes to finish.
+
When all the messages have been received, the reception process exits,
leaving the delivery processes to finish in their own time. The standard output
and error streams are closed at the start of each delivery process.
This is the default action if none of the %-od% options are present.
+
If one of the queueing options in the configuration file
(%queue_only% or %queue_only_file%, for example) is in effect, %-odb%
overrides it if %queue_only_override% is set true, which is the default
setting. If %queue_only_override% is set false, %-odb% has no effect.

*-odf*::
oindex:[%-odf%]
cindex:[foreground delivery]
cindex:[delivery,in the foreground]
This option requests ``foreground'' (synchronous) delivery when Exim has accepted
a locally-generated message. (For the daemon it is exactly the same as
%-odb%.) A delivery process is automatically started to deliver the
message, and Exim waits for it to complete before proceeding.
+
The original Exim reception process does not finish until the delivery
process for the final message has ended. The standard error stream is left open
during deliveries.
+
However, like %-odb%, this option has no effect if %queue_only_override% is
false and one of the queueing options in the configuration file is in effect.
+
If there is a temporary delivery error during foreground delivery, the
message is left on the queue for later delivery, and the original reception
process exists. See chapter <<CHAPnonqueueing>> for a way of setting up a
restricted configuration that never queues messages.


*-odi*::
oindex:[%-odi%]
This option is synonymous with %-odf%. It is provided for compatibility with
Sendmail.

*-odq*::
oindex:[%-odq%]
cindex:[non-immediate delivery]
cindex:[delivery,suppressing immediate]
cindex:[queueing incoming messages]
This option applies to all modes in which Exim accepts incoming messages,
including the listening daemon. It specifies that the accepting process should
not automatically start a delivery process for each message received. Messages
are placed on the queue, and remain there until a subsequent queue runner
process encounters them. There are several configuration options (such as
%queue_only%) that can be used to queue incoming messages under certain
conditions. This option overrides all of them and also %-odqs%. It always
forces queueing.

*-odqs*::
oindex:[%-odqs%]
cindex:[SMTP,delaying delivery]
This option is a hybrid between %-odb%/%-odi% and %-odq%.
However, like %-odb% and %-odi%, this option has no effect if
%queue_only_override% is false and one of the queueing options in the
configuration file is in effect.
+
When %-odqs% does operate, a delivery process is started for each incoming
message, in the background by default, but in the foreground if %-odi% is also
present. The recipient addresses are routed, and local deliveries are done in
the normal way. However, if any SMTP deliveries are required, they are not done
at this time, so the message remains on the queue until a subsequent queue
runner process encounters it. Because routing was done, Exim knows which
messages are waiting for which hosts, and so a number of messages for the same
host can be sent in a single SMTP connection. The %queue_smtp_domains%
configuration option has the same effect for specific domains. See also the
%-qq% option.

*-oee*::
oindex:[%-oee%]
cindex:[error,reporting]
If an error is detected while a non-SMTP message is being received (for
example, a malformed address), the error is reported to the sender in a mail
message.
+
Provided
cindex:[return code,for %-oee%]
this error message is successfully sent, the Exim receiving process
exits with a return code of zero. If not, the return code is 2 if the problem
is that the original message has no recipients, or 1 any other error. This is
the default %-oe'x'% option if Exim is called as 'rmail'.

*-oem*::
oindex:[%-oem%]
cindex:[error,reporting]
cindex:[return code,for %-oem%]
This is the same as %-oee%, except that Exim always exits with a non-zero
return code, whether or not the error message was successfully sent.
This is the default %-oe'x'% option, unless Exim is called as 'rmail'.

*-oep*::
oindex:[%-oep%]
cindex:[error,reporting]
If an error is detected while a non-SMTP message is being received, the
error is reported by writing a message to the standard error file (stderr).
cindex:[return code,for %-oep%]
The return code is 1 for all errors.

*-oeq*::
oindex:[%-oeq%]
cindex:[error,reporting]
This option is supported for compatibility with Sendmail, but has the same
effect as %-oep%.

*-oew*::
oindex:[%-oew%]
cindex:[error,reporting]
This option is supported for compatibility with Sendmail, but has the same
effect as %-oem%.

*-oi*::
oindex:[%-oi%]
cindex:[dot in incoming, non-SMTP message]
This option, which has the same effect as %-i%, specifies that a dot on a line
by itself should not terminate an incoming, non-SMTP message.
Otherwise, a single dot does terminate, though Exim does no special processing
for other lines that start with a dot.
This option is set by default if Exim is called as 'rmail'. See also %-ti%.

*-oitrue*::
oindex:[%-oitrue%]
This option is treated as synonymous with %-oi%.

*-oMa*~<'host~address'>::
oindex:[%-oMa%]
cindex:[sender host address, specifying for local message]
A number of options starting with %-oM% can be used to set values associated
with remote hosts on locally-submitted messages (that is, messages not received
over TCP/IP). These options can be used by any caller in conjunction with the
%-bh%, %-be%, %-bf%, %-bF%, %-bt%, or %-bv% testing options. In other
circumstances, they are ignored unless the caller is trusted.
+
The %-oMa% option sets the sender host address. This may include a port number
at the end, after a full stop (period). For example:

  exim -bs -oMa 10.9.8.7.1234
+
An alternative syntax is to enclose the IP address in square brackets,
followed by a colon and the port number:

  exim -bs -oMa [10.9.8.7]:1234
+
The IP address is placed in the $sender_host_address$ variable, and the
port, if present, in $sender_host_port$.

*-oMaa*~<'name'>::
oindex:[%-oMaa%]
cindex:[authentication name, specifying for local message]
See %-oMa% above for general remarks about the %-oM% options. The %-oMaa%
option sets the value of $sender_host_authenticated$ (the authenticator
name). See chapter <<CHAPSMTPAUTH>> for a discussion of SMTP authentication.

*-oMai*~<'string'>::
oindex:[%-oMai%]
cindex:[authentication id, specifying for local message]
See %-oMa% above for general remarks about the %-oM% options. The %-oMai%
option sets the value of $authenticated_id$ (the id that was authenticated).
This overrides the default value (the caller's login id) for messages from
local sources. See chapter <<CHAPSMTPAUTH>> for a discussion of authenticated
ids.

*-oMas*~<'address'>::
oindex:[%-oMas%]
cindex:[authentication sender, specifying for local message]
See %-oMa% above for general remarks about the %-oM% options. The %-oMas%
option sets the authenticated sender value in $authenticated_sender$. It
overrides the sender address that is created from the caller's login id for
messages from local sources. See chapter <<CHAPSMTPAUTH>> for a discussion of
authenticated senders.

*-oMi*~<'interface~address'>::
oindex:[%-oMi%]
cindex:[interface address, specifying for local message]
See %-oMa% above for general remarks about the %-oM% options. The %-oMi% option
sets the IP interface address value. A port number may be included, using the
same syntax as for %-oMa%. The interface address is placed in
$interface_address$ and the port number, if present, in $interface_port$.

*-oMr*~<'protocol~name'>::
oindex:[%-oMr%]
cindex:[protocol,incoming -- specifying for local message]
See %-oMa% above for general remarks about the %-oM% options. The %-oMr% option
sets the received protocol value that is stored in $received_protocol$.
However, this applies only when %-bs% is not used. For interactive SMTP input
(%-bs%), the protocol is always ``local-'' followed by one of the standard SMTP
protocol names (see the description of $received_protocol$ in section
<<SECTexpvar>>). For %-bS% (batch SMTP) however, the protocol can be set by
<<%-oMr%.

*-oMs*~<'host~name'>::
oindex:[%-oMs%]
cindex:[sender host name, specifying for local message]
See %-oMa% above for general remarks about the %-oM% options. The %-oMs% option
sets the sender host name in $sender_host_name$. When this option is present,
Exim does not attempt to look up a host name from an IP address; it uses the
name it is given.

*-oMt*~<'ident~string'>::
oindex:[%-oMt%]
cindex:[sender ident string, specifying for local message]
See %-oMa% above for general remarks about the %-oM% options. The %-oMt% option
sets the sender ident value in $sender_ident$. The default setting for local
callers is the login id of the calling process.

*-om*::
oindex:[%-om%]
cindex:[Sendmail compatibility,%-om% option ignored]
In Sendmail, this option means ``me too'', indicating that the sender of a
message should receive a copy of the message if the sender appears in an alias
expansion. Exim always does this, so the option does nothing.

*-oo*::
oindex:[%-oo%]
cindex:[Sendmail compatibility,%-oo% option ignored]
This option is ignored. In Sendmail it specifies ``old style headers'', whatever
that means.

*-oP*~<'path'>::
oindex:[%-oP%]
cindex:[pid (process id),of daemon]
cindex:[daemon,process id (pid)]
This option is useful only in conjunction with %-bd% or %-q% with a time
value. The option specifies the file to which the process id of the daemon is
written. When %-oX% is used with %-bd%, or when %-q% with a time is used
without %-bd%, this is the only way of causing Exim to write a pid file,
because in those cases, the normal pid file is not used.

*-or*~<'time'>::
oindex:[%-or%]
cindex:[timeout,for non-SMTP input]
This option sets a timeout value for incoming non-SMTP messages. If it is not
set, Exim will wait forever for the standard input. The value can also be set
by the %receive_timeout% option. The format used for specifying times is
described in section <<SECTtimeformat>>.

*-os*~<'time'>::
oindex:[%-os%]