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* SHOULD YOU USE THIS PACKAGE? *

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Since version 4.50, Exim has the content-scanning extension formerly

known as "exiscan" built-in. It has a number of advantages and

disadvantages compared to SA-Exim.

Advantages of built-in content-scanning interface:

 * One less configuration file to edit.

 * Spam control policy integrates better with Exim's ACL system.

 * It's possible to tell SA which user to scan for (the -u parameter of

   spamc). SA-Exim can't do that (yet).

 * Finer control over the mail header is possible, but not in a clean

   way (it involves putting all header fields you might possibly want

   to add in the report template, and using rather complicated

   expansion expressions to extract the wanted ones from

   $spam_report). At any rate, you can choose a prefix different from

   "X-Spam-".

Advantages of SA-Exim:

 * It is possible to use the report_safe feature, which turns mail

   deemed to be spam into a message/rfc822 attachment of a report

   message. (Note however that if you do, then any X-SA-* fields added

   to help the greylisting module can't be removed.)

 * All the add_header and rewrite_header options in

   /etc/spamassassin/local.cf will be obeyed. In other words,

   everything will be *almost* as if you filtered the mail through

   spamassassin on the command line.

 * So-called teergrubing ("tarpitting") is possible in a way that

   isn't possible with exiscan (I'm not in any way saying that it

   works as a counterattack against spammers).

 * You can simply add the sa-exim package to a standard exim4

   installation and it should, in principle, instantly work (except

   you have to uncomment one line in sa-exim.conf).

Both alternatives enable you to defer, greylist, reject, and blackhole

mail, optionally saving copies, at configurable score levels.

*****************

* CONFIGURATION *

*****************

This version of the sa-exim package defaults to placing a configuration

sniplet in /etc/exim4/conf.d/. Depending on what you have answered to the

DebConf questions while configuring Exim4, the module will be loaded

automatically, or human intervention is required.

To find out what configuration file Exim4 is using, issue:

  $ exim4 -bV | tail -1

  Configuration file is /path/to/configfile

If /path/to/configfile shows:

  - /etc/exim4/exim4.conf

    You are using the hand-crafted configuration file.

	See the 'HAND-CRAFTED' section below.

  - /var/lib/exim4/config.autogenerated

    You are using the debianized configuration scheme - with either

    'split' or 'unsplit' configuration file.

	See the 'DEBIANIZED' section below.

HAND-CRAFTED

------------

Use 'grep "local_scan_path" /etc/exim4/exim4.conf" to see if the sa-exim

line is included in the configuration. If grep returns something, check

if it matches the following line. If grep returns nothing, you have to

manually add the following line to the exim4.conf file and restart exim4.

    local_scan_path = /usr/lib/exim4/local_scan/sa-exim.so

Change or add the line above and manually restart exim4 by issuing

'invoke-rc.d exim4 reload' or '/etc/init.d/exim4 reload' as root.

DEBIANIZED

----------

Use 'grep "local_scan_path" /var/lib/exim4/config.autogenerated' to

see if the sa-exim line is included in the configuration. If grep

returns something, you're set and already using the sa-exim module. If

grep returns nothing, we need to figure out a few things:

Issue:

	$ grep "use_split_config" /etc/exim4/update-exim4.conf.conf

      dc_use_split_config='true'

If your result shows 'false' where mine shows 'true', then you're

using the unsplit configuration, generated from

/etc/exim4/exim4.conf.template.  If you haven't customized that file

you could edit /etc/exim4/update-exim4.conf.conf by hand, change the

'false' to 'true' and issue 'update-exim4.conf' as root. Then, check

again if the sa-exim module line is included. It should. If it still

isn't: mail me. If it is, restart exim4 by issuing 'invoke-rc.d exim4

restart' or '/etc/init.d/exim4 restart' as root. If you *have*

customized /etc/exim4/exim4.conf.template, then you'd better stick

with the unsplit configuration scheme and add the local_scan_path

setting by hand, like with the hand-crafted configuration file.

Next, read all about greylisting and sa-exim:

***************

* GREYLISTING *

***************

Notes on greylisting with sa-exim.

If you use SpamAssassin 3.0 or better, you do not need to patch it, you

can just use the Greylisting module shipped with sa-exim.

The only thing you need to do to enable it, is to copy the 4 lines below

loadplugin in the greylisting README, and adjust the score if you wish (see

README.Greylisting for details).

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* PROBLEMS WITH BAYES AUTO-EXPIRY *

***********************************

When scanning mail during the SMTP dialogue there is somewhat limited

time before the remote host gives up, even if they should wait for at

least ten minutes. To avoid Exim returning a temporary error status,

or the remote host giving up prematurely and in some cases for good,

SA-Exim overrides Exim's timeout handler and accepts the message if

SpamAssassin takes too long, by default 240 seconds.

Using SpamAssassin's Bayesian learning module means that it will

automatically expire old tokens when its database has grown too large.

That can take several minutes. If it takes too long, SA-Exim will

abort it, meaning that SpamAssassin will run auto-expiry again next

time, and be aborted, and so on...

If this happens, you have a few remedies:

1) Set SAtimeout to a higher value in /etc/exim4/sa-exim.conf.

2) Run sa-learn --force-expire periodically. How you run it depends on

   how you've configured SpamAssassin. Running it as Debian-exim may

   be sufficient.

2 a) In addition, you can add

   bayes_auto_expire 0

   to /etc/spamassassin/local.cf. This may not be a good idea if

   SpamAssassin, for whatever reason, is also used as a more

   traditional filter from e.g. .procmailrc, as all users will need to

   run sa-learn --force-expire then.

2 b) If you get a lot of mail, consider adding

   bayes_learn_to_journal 1

   to local.cf. See the Mail::SpamAssassin::Conf(3) manual page for

   more information.

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* NOTICE ABOUT SPAMC CONFIG FILE *

**********************************

Recent versions of spamc can read command-line parameters and switches

from a configuration file called /etc/spamassassin/spamc.conf. If that

file specifies conflicting options, it will prevent SA-Exim from

working. For now, you'll have to make sure that it doesn't.

 -- Magnus Holmgren <holmgren@debian.org>, Tue, 24 Jun 2008 14:27:59 +0200