There is a new version of this tutorial available for Ubuntu 13.10 (Saucy Salamander).

Virtual Users And Domains With Postfix, Courier And MySQL (Ubuntu 7.10) - Page 4

9 Install amavisd-new, SpamAssassin, And ClamAV

To install amavisd-new, spamassassin and clamav, run the following command:

apt-get install amavisd-new spamassassin clamav clamav-daemon zoo unzip bzip2 unzoo libnet-ph-perl libnet-snpp-perl libnet-telnet-perl nomarch lzop pax

Afterwards we must configure amavisd-new. The configuration is split up in various files which reside in the /etc/amavis/conf.d directory. Take a look at each of them to become familiar with the configuration. Most settings are fine, however we must modify three files:

First we must enable ClamAV and SpamAssassin in /etc/amavis/conf.d/15-content_filter_mode by uncommenting the @bypass_virus_checks_maps and the @bypass_spam_checks_maps lines:

vi /etc/amavis/conf.d/15-content_filter_mode

The file should look like this:

use strict;

# You can modify this file to re-enable SPAM checking through spamassassin
# and to re-enable antivirus checking.

#
# Default antivirus checking mode
# Uncomment the two lines below to enable it back
#

@bypass_virus_checks_maps = (
   \%bypass_virus_checks, \@bypass_virus_checks_acl, \$bypass_virus_checks_re);


#
# Default SPAM checking mode
# Uncomment the two lines below to enable it back
#

@bypass_spam_checks_maps = (
   \%bypass_spam_checks, \@bypass_spam_checks_acl, \$bypass_spam_checks_re);

1;  # insure a defined return

And then you should take a look at the spam settings and the actions for spam-/virus-mails in /etc/amavis/conf.d/20-debian_defaults. There's no need to change anything if the default settings are ok for you. The file contains many explanations so there's no need to explain the settings here:

vi /etc/amavis/conf.d/20-debian_defaults

[...]
$QUARANTINEDIR = "$MYHOME/virusmails";

$log_recip_templ = undef;    # disable by-recipient level-0 log entries
$DO_SYSLOG = 1;              # log via syslogd (preferred)
$syslog_ident = 'amavis';    # syslog ident tag, prepended to all messages
$syslog_facility = 'mail';
$syslog_priority = 'debug';  # switch to info to drop debug output, etc

$enable_db = 1;              # enable use of BerkeleyDB/libdb (SNMP and nanny)
$enable_global_cache = 1;    # enable use of libdb-based cache if $enable_db=1

$inet_socket_port = 10024;   # default listenting socket

$sa_spam_subject_tag = '***SPAM*** ';
$sa_tag_level_deflt  = 2.0;  # add spam info headers if at, or above that level
$sa_tag2_level_deflt = 6.31; # add 'spam detected' headers at that level
$sa_kill_level_deflt = 6.31; # triggers spam evasive actions
$sa_dsn_cutoff_level = 10;   # spam level beyond which a DSN is not sent

$sa_mail_body_size_limit = 200*1024; # don't waste time on SA if mail is larger
$sa_local_tests_only = 0;    # only tests which do not require internet access?

[...]
$final_virus_destiny      = D_DISCARD;  # (data not lost, see virus quarantine)
$final_banned_destiny     = D_BOUNCE;   # D_REJECT when front-end MTA
$final_spam_destiny       = D_BOUNCE;
$final_bad_header_destiny = D_PASS;     # False-positive prone (for spam)
[...]

Finally, edit /etc/amavis/conf.d/50-user and add the line $pax='pax'; in the middle:

vi /etc/amavis/conf.d/50-user

use strict;

#
# Place your configuration directives here.  They will override those in
# earlier files.
#
# See /usr/share/doc/amavisd-new/ for documentation and examples of
# the directives you can use in this file
#

$pax='pax';

#------------ Do not modify anything below this line -------------
1;  # insure a defined return

Afterwards, run these commands to add the clamav user to the amavis group and to restart amavisd-new and ClamAV:

adduser clamav amavis
/etc/init.d/amavis restart
/etc/init.d/clamav-daemon restart
/etc/init.d/clamav-freshclam restart

Now we have to configure Postfix to pipe incoming email through amavisd-new:

postconf -e 'content_filter = amavis:[127.0.0.1]:10024'
postconf -e 'receive_override_options = no_address_mappings'

Afterwards append the following lines to /etc/postfix/master.cf:

vi /etc/postfix/master.cf

[...]
amavis unix - - - - 2 smtp
        -o smtp_data_done_timeout=1200
        -o smtp_send_xforward_command=yes

127.0.0.1:10025 inet n - - - - smtpd
        -o content_filter=
        -o local_recipient_maps=
        -o relay_recipient_maps=
        -o smtpd_restriction_classes=
        -o smtpd_client_restrictions=
        -o smtpd_helo_restrictions=
        -o smtpd_sender_restrictions=
        -o smtpd_recipient_restrictions=permit_mynetworks,reject
        -o mynetworks=127.0.0.0/8
        -o strict_rfc821_envelopes=yes
        -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks
        -o smtpd_bind_address=127.0.0.1

Then restart Postfix:

/etc/init.d/postfix restart

Now run

netstat -tap

and you should see Postfix (master) listening on port 25 (smtp) and 10025, and amavisd-new on port 10024:

[email protected]:/etc/postfix# netstat -tap
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 localhost.localdo:10024 *:*                     LISTEN     14770/amavisd (mast
tcp        0      0 localhost.localdo:10025 *:*                     LISTEN     15800/master
tcp        0      0 localhost.localdo:mysql *:*                     LISTEN     5742/mysqld
tcp        0      0 *:smtp                  *:*                     LISTEN     15800/master
tcp6       0      0 *:imaps                 *:*                     LISTEN     13290/couriertcpd
tcp6       0      0 *:pop3s                 *:*                     LISTEN     13359/couriertcpd
tcp6       0      0 *:pop3                  *:*                     LISTEN     13320/couriertcpd
tcp6       0      0 *:imap2                 *:*                     LISTEN     13253/couriertcpd
tcp6       0      0 *:www                   *:*                     LISTEN     4961/apache2
tcp6       0      0 *:ssh                   *:*                     LISTEN     3725/sshd
tcp6       0      0 server1.example.com:ssh ::ffff:192.168.0.2:4670 ESTABLISHED3783/0
[email protected]:/etc/postfix#

 

10 Install Razor, Pyzor And DCC And Configure SpamAssassin

Razor, Pyzor and DCC are spamfilters that use a collaborative filtering network. To install them, run

apt-get install razor pyzor dcc-client

Now we have to tell SpamAssassin to use these three programs. Edit /etc/spamassassin/local.cf and add the following lines to it:

vi /etc/spamassassin/local.cf

[...]
#dcc
use_dcc 1
dcc_path /usr/bin/dccproc

#pyzor
use_pyzor 1
pyzor_path /usr/bin/pyzor

#razor
use_razor2 1
razor_config /etc/razor/razor-agent.conf

#bayes
use_bayes 1
use_bayes_rules 1
bayes_auto_learn 1

Then we must enable the DCC plugin in SpamAssassin. Open /etc/spamassassin/v310.pre and uncomment the loadplugin Mail::SpamAssassin::Plugin::DCC line:

vi /etc/spamassassin/v310.pre

# This is the right place to customize your installation of SpamAssassin.
#
# See 'perldoc Mail::SpamAssassin::Conf' for details of what can be
# tweaked.
#
# This file was installed during the installation of SpamAssassin 3.1.0,
# and contains plugin loading commands for the new plugins added in that
# release.  It will not be overwritten during future SpamAssassin installs,
# so you can modify it to enable some disabled-by-default plugins below,
# if you so wish.
#
# There are now multiple files read to enable plugins in the
# /etc/mail/spamassassin directory; previously only one, "init.pre" was
# read.  Now both "init.pre", "v310.pre", and any other files ending in
# ".pre" will be read.  As future releases are made, new plugins will be
# added to new files, named according to the release they're added in.
###########################################################################

# DCC - perform DCC message checks.
#
# DCC is disabled here because it is not open source.  See the DCC
# license for more details.
#
loadplugin Mail::SpamAssassin::Plugin::DCC

# Pyzor - perform Pyzor message checks.
#
loadplugin Mail::SpamAssassin::Plugin::Pyzor

# Razor2 - perform Razor2 message checks.
#
loadplugin Mail::SpamAssassin::Plugin::Razor2

# SpamCop - perform SpamCop message reporting
#
loadplugin Mail::SpamAssassin::Plugin::SpamCop

# AntiVirus - some simple anti-virus checks, this is not a replacement
# for an anti-virus filter like Clam AntiVirus
#
#loadplugin Mail::SpamAssassin::Plugin::AntiVirus

# AWL - do auto-whitelist checks
#
loadplugin Mail::SpamAssassin::Plugin::AWL

# AutoLearnThreshold - threshold-based discriminator for Bayes auto-learning
#
loadplugin Mail::SpamAssassin::Plugin::AutoLearnThreshold

# TextCat - language guesser
#
#loadplugin Mail::SpamAssassin::Plugin::TextCat

# AccessDB - lookup from-addresses in access database
#
#loadplugin Mail::SpamAssassin::Plugin::AccessDB

# WhitelistSubject - Whitelist/Blacklist certain subject regular expressions
#
loadplugin Mail::SpamAssassin::Plugin::WhiteListSubject

###########################################################################
# experimental plugins

# DomainKeys - perform DomainKeys verification
#
# External modules required for use, see INSTALL for more information.
# Note that this may be redundant if you also plan to use the DKIM plugin.
#
#loadplugin Mail::SpamAssassin::Plugin::DomainKeys

# MIMEHeader - apply regexp rules against MIME headers in the message
#
loadplugin Mail::SpamAssassin::Plugin::MIMEHeader

# ReplaceTags
#
loadplugin Mail::SpamAssassin::Plugin::ReplaceTags

You can check your SpamAssassin configuration by executing:

spamassassin --lint

It shouldn't show any errors.

Restart amavisd-new afterwards:

/etc/init.d/amavis restart

Falko Timme

About Falko Timme

Falko Timme is an experienced Linux administrator and founder of Timme Hosting, a leading nginx business hosting company in Germany. He is one of the most active authors on HowtoForge since 2005 and one of the core developers of ISPConfig since 2000. He has also contributed to the O'Reilly book "Linux System Administration".

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