If you plan to run amavisd-new, you don't need to run spamassassin separately (usually
via spamd).  Amavisd-new calls spamassassin internally to scan messages.  You can
also install clamav and enable virus scanning in the configuration file.

RUNTIME DEPENDENCIES:
ZeroMQ library -- since amavisd-new version > 2.8.x, depends heavily on ZeroMQ.

OPTIONAL DEPENDENCIES:

FOR SPAMASSASSIN:
See https://slackbuilds.org/slackbuilds/15.0/network/spamassassin/README

FOR AMAVISD-NEW:
p0f
perl-Convert-UUlib (if you need do_ascii, which is unsafe)
unrar
p7zip or 7zip

SLACKBUILD CHANGELOG:
Script and package changes introduced in version >= 2.6.6
1. logrotate file is renamed amavisd-new.
2. rc script is renamed to rc.amavisd-new
3. logfile in the logrotate script is renamed to amavisd-new.log.  Make sure
   you change the logfile in the amavisd.conf file and rename the log file.
   Look for, $LOGFILE directive in the configuration file.
4. Remember to update your rc.local and rc.local_shutdown scripts accordingly.
5. With version 2.7, a new process amavisd-signer is spawned to take care
   of dkim signing.  Please read RELEASE_NOTES in the documentation.
6. With version > 2.8, rc script has been overhauled to start 3 daemons, more
   notes are in the rc script.

SETUP:
1. Create amavis user/group, before running the script.  You don't have to follow
uid/gid strictly.  This is just an example, you may as well use any other uid/gid
combination.
   groupadd -r -g 211 amavis
   useradd -r -d -m /var/lib/amavis -s /bin/bash -u 211 -g 211 amavis

2. Make sure you have write perms for amavis group to amavis home (in this
   case, /var/lib/amavis)

3. Create /var/log/amavisd.log file, change perms to allow write access
   to amavisd user/group.

4. Add amavis user to clamav group and set "AllowSupplementaryGroups yes"
   in fresclam.conf to allow amavis to scan messages.

5. To scan messages using spamassassin, you need to provide write access
   to amavis user to /var/lib/spamassassin, which is the default.  If the
   directory doesn't exist, it will be created by spamassassin but the
   permissions will correspond to the user invoking it.

6. Edit /etc/amavisd.conf.  Verbose version of config file is included to
   aid in configuration.

7. You can turn on debugging in log file with $sa_debug configuration
   variable in /etc/amavisd.conf.