Listing 2 Postfix master.cf edits

Put the following lines in your Postfix main.cf file:

content_filter = scan:127.0.0.1:10025
receive_override_options = no_address_mappings

The content_filter tells Postfix to send all mail through the service 
called 'scan' on port 10025. We'll set up clamsmtpd to listen on this 
port later.

Next we add the following to the Postfix master.cf file:

# AV scan filter (used by content_filter)
scan      unix  -       -       n       -       16      smtp
        -o smtp_send_xforward_command=yes
# For injecting mail back into postfix from the filter
127.0.0.1:10026 inet  n -       n       -       16      smtpd
        -o content_filter=
        -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks
        -o smtpd_helo_restrictions=
        -o smtpd_client_restrictions=
        -o smtpd_sender_restrictions=
        -o smtpd_recipient_restrictions=permit_mynetworks,reject
        -o mynetworks_style=host
        -o smtpd_authorized_xforward_hosts=127.0.0.0/8ServerTokens OS