Merak Mail Server Suite   
http://www.icewarp.com

Multiple awards winner mail server with ultimate features, complete security and guaranteed stability. Provides a wide range of optional components and services including secured mail services with multiple domain support(SMTP, POP3, IMAP), user-friendly Web-Mail (Outlook-like interface), Anti-Spam with updates (SpamAssassin, SPF, Bayes, SURBL, ChallengeResponse, DomainKeys, Greylisting), Anti-Virus with updates, Instant Messaging (based on the Jabber XMPP protocol, also accessiale via web, supporting AOL, ICQ, MSN, Yahoo and other Jabber and Merak servers), GroupWare (accessible via web and Outlook), FTP (secure FTP server with many features and the system integration), load balancing (ODBC support), monitoring and report facilities (charts and reports), developers API, several account types (mailing lists, list servers, executables, catalogs, static routes, remote accounts, users, domains), system alert tools, remote administration and many other features and tools. Merak mail server suite is a reliable, easy to use, and affordable communication solution that is used by more than 40 million users worldwide. Available on Windows and Unix based systems.

Aloaha SPAM rejector   
http://www.aloaha.com

Innovative server based AntiSPAM Solution. Incl. Sender Policy Framework and Sender ID Support! Does not depend on IIS or Exchange. Works together with every SMTP Server. Mail archiving, Remote Black-/Whitelists, relaxed greylisting, script engine and lots of other features. Does not accept spam. Rejects spam before reaching the SMTP Server. Now also with POP3 Interface (downloader) and SINK Plugin! .