If you want to stop spam then check out this website at www.spamihilator.com
It offers several ways of stopping spam including a learning mode based on Baysean statistics and many good filters including a DCC filter. It's all for free and I have successfully been using this for the past year both with Outlook and more recently with Thunderbird.
If you need any more info just ask

The Bitdefender's Antispam is avery good one too if you using Outlook Express... So try it