Microsoft Outlook 2003 includes a basic SPAM filter. Here are the steps to enable it:

1. Make sure that Microsoft Outlook 2003 is operating in Cached mode. If the word "Online" or "Offline" appears in the bottom right corner of MS Outlook, then you need to switch to Cached mode; instructions: click here.
2. To turn on the SPAM filter, click on Actions in Outlook's top menu bar, then click on Junk E-mail, and then click on Junk E-mail Options. Screenshot:
   
   
3. In the Junk E-mail Options, choose High - this is the most effective setting:
   
   
4. Microsoft Outlook 2003 will from this point on move any e-mails that it deems to be SPAM into the Junk E-mail folder. You need to go through this folder once in a while to clean it out AND to check for e-mails caught mistakenly by the SPAM filter.
   
   
5. If there is an e-mail in the Junk E-mail folder that is not SPAM, right click on the e-mail, click on Junk E-mail -> Mark as Not Junk.
   
   
6. Welcome to a more productive world !