clamdrib is a Thunderbird extension which scans incoming mail using open source ClamAV and blocks any virus/malware-infected email. It can prevent you from sending infected emails to Windoze users unknowingly.
Here are some steps to get it working:
1. Install clamassassin, clamav, clamav-base, clamav-daemon and clam-freshclam.
2. In a terminal window, sudo dpkg-reconfigure clamav-base. Accept all the defaults except:
"Socket type" - Change this to TCP
"IP address Clamd will listen on" - Change this to localhost
3. Reboot your computer and you should be good to go.