Untangle (www.untangle.com) -- Free Spam Blocker enables administrators to block spam at the gateway before it ever reaches the users.
* Leverage the best spam filtering techniques including Bayesian Filters, Razor, realtime block lists (RBLs), OCR for image spam and tarpitting
More Info: http://www.untangle.com/Spam-Blocker
We are not a loved organization, but we are a respected one. -- John Fisher