Summary: How to avoid spam mail

Thanks to many people who responded.
Most recommended looking up the following websites:

Use procmail at 
http://www.procmail.org

There are some spam avoidance code examples at 
http://www.sendmail.org 

Spam Prevention Early Warning System:
http://www.spews.org/

Spam Cop Blocking List information:

http://spamcop.net/fom-serve/cache/294.html
Yahoo! - Official partner of 2002 FIFA World Cup
http://fifaworldcup.yahoo.com