Still on the topic of combating spam, another tool you might want to take a look at is Spamihilator. This program acts as a “go-between” from the mail server and your mail client. Essentially, it works this way:

1. All mail is delivered directly to your local installed copy of Spamihilator.
2. Spamihilator filters the messages (based on a Bayes learning algorithm).
3. Your email client retrieves the filtered message from Spamihilator.

This intermediate step prevents the spam from ever reaching your Inbox. Of course, you need to configure your email client to work with Spamihilator and there are extensive instructions available on the website.

While I have not personally used it, it looks like a good alternative for users not using Outlook (if you are using Outlook, use SpamBayes instead), so now Outlook Express/Thunderbird/etc. users have an evolving free spam prevention tool.