I believe GWAVA runs on MS too if you are still using a MS NOS.
I have tried $4000.00 solutions, $50.00 solutions, my own Python scropting solutions and much more over a 4 year period.
GWAVA is by FAR the best system I have come across. It is VERY small, VERY robust, VERY efficient, VERY resourceful. It will un on whatever server you can cram it into without slowing thigs down.
http://www.beginfinite.com
Now if GWAVA won't fit your network due to compatibility issues, GW Guardian is MS based (even though designed for GroupWise) but also does heuristic, address, known spam scanning, (as does GWAVA), incorporates your existing AV solution and scans OUTSIDE the MTA or PO. NOTE: GWGuardian is about $1500.00 and requires a dedicated dual processor server, they will provide a preinstalled, turnkey box for about $5000.00 or so. You'll have to do a simple search for gwguardian, I think that's the url even but not positive, it's been a while.
All the other cheapies, Spam Assasin etc. usually only incorporate RBL and some scanning options such as adress blocking (which is VERY ineefective)but block too much wanted mail. The issue with low cost solutions is they have too many false positives (incorrectly blocked email) and MOST do not let your train the heuristic scans or tweak them for accuracy. Many low cost solutions are just an easy address blocking interface that leave it to the user to build block lists, no diferent than creating email ruls in the client blocking lists, this should be done at the server BY the administator so the mail isn't hitting the desktops and filling up your server with crap to begin with, as well as they also allow viral emails into the server.
If you want a GOOD network based solution that takes the burden OFF the user, spend the money and do it right.
It seems that I am forever removing useless spam protection for clients that "Got a great deal and figured it was worth a try", and replacing it with more effective and far more costly solutions.
