A SMTP virus scanning system
ClamSMTP is an SMTP filter that allows you to check for viruses using the ClamAV anti-virus software. It accepts SMTP connections and forwards the SMTP commands and responses to another SMTP server. The 'DATA' email body is intercepted and scanned before forwarding. It aims to be lightweight, reliable, and simple rather than have a myriad of options. It's written in C without major dependencies. If you need more options then you could use something big like AMaViS which is written in PERL and can do almost anything. Written with the Postfix mail server in mind it can be configured as a Postfix Content Filter. It can also be used as a transparent proxy to filter an entire network's SMTP traffic at the router.