Spam filtering device

[Mr N8]

Is there any hardware that I can put on my network that would do this? A software only solution is not ideal, as some of my users get over 100 messages a day, and to preview and filter is a big time waster, also. I have the email server locally, so if the device were able to scan all incoming message / traffic to the server, that would be all that I needed. Any advice would be appreciated. Thanks a lot!

Nate