The Anti-Spam SMTP Proxy (ASSP) Server project aims to create an open source platform-independent SMTP Proxy server which implements auto-whitelists, self learning Bayesian, Greylisting, DNSBL, DNSWL, URIBL, SPF, SRS, Backscatter, Virus scanning, attachment blocking, Senderbase and multiple other filter methods. Click 'Browse all files' to download the professional version 2.4.1 build 14200.
V1 development has been stopped in May 2014. Possibly there will be done some bugfixing until end of 2014. EOL of V1 is anounced for the 31 December 2014.
Please upgrade to V2, which is and will be actively maintained.