I have been fighting this was for years now. I started out with old school program that ran on a windows 2000 server box. That evolved into bigger windows box, and was supplemented with an outside service. Then we bought 2 IronPort boxes, and used them to replace the old dated program, and we found we no longer needed the outside service to keep the traffic off of our mail server. This is what IronPort does the best. Drops bad email. :D