eWall SMTP Proxy 1.0
This is an SMTP proxy that works with any mail server.
It supports major anti-virus software and can be easily integrated with popular spam detecting software like SpamAssassin. It has a various security options that will protect your mail sever from vandals when they request a connection, save your precious bandwidth and control the mail transaction. The flexible system of filters let you develop the new services for your customers. The filters can be created globally or per user or domain.