A Free Anti-Virus and Anti-Spam Filter for Mail Servers
MailScanner is an email-security and anti-spam system for Mail Transfer Agents. According to the documentation, "The software works with any Unix-based system and is compatible with a wide range of mail transports. It comes with support for any combination of 25 different virus scanner packages, including the free ClamAV scanner, and its design allows the use of multiple virus scanners in parallel to increase the level of security."