virus-scanning SMTP proxy

 ClamSMTP is an SMTP proxy daemon that checks for viruses using the ClamAV
 anti-virus software. It can act as a traditional SMTP proxy with publicly
 accessible ports or as a transparent proxy, where SMTP traffic is redirected
 to the ClamSMTP by your router.
 .
 ClamSMTP aims to be lightweight, reliable, and simple rather than have a
 myriad of options. It is written in C without major dependencies. ClamSMTP
 does not do general spam filtering, it only scans for viruses.
 .
 You do not need a local mail-transport-agent installed, since this server can
 forward to a remote one.