[SpamAssassin]
                                            ^
                                            |
Email --> [(Port 25) Postfix] --> [(10024) amavisd-new] --> [(10025) Postfix] --> Mailbox
                                            |
                                            v
                                         [ClamAV]

apt-get install amavisd-new spamassassin clamav clamav-daemon

Descompresores y utilidades 

apt-get install unrar-free zoo unzip bzip2 libnet-ph-perl libnet-snpp-perl libnet-telnet-perl nomarch lzop

amavis

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

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

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

Configurar lo que tenemos que hacer con los spam y los virus:

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

Por ejemplo podemos dejar pasar el spam, aunque lo marquemos:

$final_spam_destiny       = D_PASS;

Por último:

adduser clamav amavis
/etc/init.d/amavis restart

Actualizamos el antivirus:

freshclam

/etc/init.d/clamav-daemon restart

Añadimos a la configuración de postfin las siguientes líneas:

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


/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

/etc/init.d/postfix restart

Comporbamos si estamos escuchando por los puertos:

netstat -tap

tcp        0      0 localhost:10024         *:*                     LISTEN      7487/amavisd (maste
tcp        0      0 localhost:10025         *:*                     LISTEN      14341/master    



spamassassin

Lo activamos

nano /etc/default/spamassassin

ENABLED=1


/etc/spamassassin/local.cf

/etc/init.d/spamassassin restart