eWall SMTP Proxy Free

eWall is a Windows based gateway between the Internet and your mail server. It monitors the SMTP traffic in real-time, catching the majority of spam and viruses. The chain of flexible filters stops more than 95% of unwanted emails out of the box (more than 99% with Message Sniffer), dropping the mail server load by more than 90%. eWall doesnt require maintenance and includes optional self-updating components (ClamAV, Message Sniffer), that seamlessly work with and protect your mail environment from spam and viruses 24 hours a day, 7 days a week.
eWall is built on top of time-proven and reliable technologies. PHP is used as a flexible and powerful scripting engine, allowing you to write filters of any complexity. Any standard PHP drivers or libraries can be used in eWalls event-driven environment. The powerful PostgreSQL database is used to keep the statistics and index quarantined messages, emails and IP-lists, and track the session history. XML-RPC transport is used to manage and watch the eWall remotely from the Control Panel.
All filters represent open-sourced snippets of PHP code, stored in the eWall Repository. The Repository is an XML-formatted file with well documented structure, allowing you to easily modify existing, or quicky develop new, filters, containing the newest anti-spam and anti-virus techniques. The Repository shipped with eWall already contains most of major anti-spam and anti-virus filters, such as DNSBL, SPF, SURBL, Attachment filtering, Country filtering, SpamAssassin, ClamAV and various misc tests. Get eWall and take it for a spin to see what it can actually do for you!
NOTE: For the free version you need to register here. The Free edition is limited to the number of mailboxes and intended for small companies.System requirementsIntel Pentium 4 (2.8 GHz) CPU or better
2 GB of RAM