Barracuda network, the basics
This is probably the most effective one on the market these days. The Barracuda firewall utilizes various techniques to identify spam in your email. Once the spam is identified as such, you can have it discarded or placed in a holding area. Spam emails are identified by the Barracuda firewall before it even reaches your inbox. This fact alone can save you hours you would normally have to spend going through emails everyday.