Filter Email and Block Spam

• Use the Mail Filter Utility 
  The Mail Filter Utility allows you to enable automatic spam filtering on the server. You may also set up the filter to block emails by keyword.
• Mail Filter Utility - design, capabilities and use
• Using Procmail (Advanced) - an introduction to Procmail with several examples of common tasks such as filtering email, forwarding, and auto-reply.
• Managing Spam at UCSD