I was wondering if there were any anit-spam filtering software that could be recommended to sit on a Windows 2003 SBS running Exchange with Avast! antivirus with plugins for Exchange and ISA.
I saw a thread for Spamihilator, but this is a client side software. The filtering provided with Exchange is not very good since if messages are being mis-categorized, you can only whitelist the sender. But that is bad for us because the sender addresses are often forged, so it would whitelist some spam when we just want to whitelist a particular sender.
Ideally, I would want a server side software that would use a form of Bayesian filtering. And then a plugin for Outlook 2003 to be able to mark a message as spam or not to update the filter on the server.