ClamAV® is an open source antivirus engine for detecting trojans, viruses, malware & other malicious threats.
Using ClamAV with a mail server... on a Debian System... is fairly simplistic to set up.
First: install these packages...
|clamav||anti-virus utility for Unix - command-line interface|
|clamav-base||anti-virus utility for Unix - base package|
|clamav-daemon||anti-virus utility for Unix - scanner daemon|
|clamav-freshclam||anti-virus utility for Unix - virus database update utility|
|clamdscan||anti-virus utility for Unix - scanner client|
|clamsmtp||virus-scanning SMTP proxy|
Then add the appropriate lines to your MTA configuration file(s). In exim it would look something like this...
spamd_address= 127.0.0.1 783
These are the defaults... if you are running clamav on another server substitute the local host/port for the ip/port of that server.