Configure SpamHaus or other RBL provider with Exchange 2007

Go into your Exchange Management Console
Click on Organization Configuration>Edge Transport or Hub Transport depending on what your setup is like.
Click on the anti-spam tab
Double Click on IP block list providers
Click on the providers tab and click add
For the provider name put SpamHAUS and zen.spamhaus.org for the lookup domain.  Restart your Exchange Transport services.  You are now filtering IP’s based on SpamHaus RBL list.