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
There are two major products that come out of Berkeley: LSD and UNIX. We don't believe this to be a coincidence. -- Jeremy S. Anderson