There is a wonderful Spam filter available to Exchange 2003, www.spamhaus.org. This is nothing more than a link to a database of known spammers.
- The Spamhaus Block List (SBL) is a realtime blocklist of spam sources and spam services.
- The Exploits Block List (XBL) is a realtime blocklist of illegal third-party exploits (proxies/worms/trojans).
- There are complete instructions on the Web site to use the service, which is free.