SpamSoap
Scott Hanselman blogs about SpamSoap, a server side Spam filter solution that doesn’t need to be installed on your email host. You can do this by routing your email (by changing your MX record) to the SpamSoap Servers, and they filter the spam for you. They redirect the good stuff to the original email account, and the suspected spam to a spam email account. Sounds like a great solution. I use Webhosting4Life and since they don’t offer spam filtering, this solution would solve that problem. The only issue I have is the price. At $25/month SpamSoap is more expensive than my hosting provider.
DonXML