Enhance Your Mail Server With ASSP (Anti-Spam SMTP Proxy)
ASSP stands for Anti-Spam SMTP Proxy. The ASSP server project is an Open Source platform-independent transparent SMTP proxy server that leverages numerous methodologies and technologies to both rigidly and adaptively identify spam. In short ASSP is the most kickass solution that is both free and works great. It reduced spam to an absolute minimum for me.