Go into your Exchange Management Console\nClick on Organization Configuration>Edge Transport or Hub Transport depending on what your setup is like.\nClick on the anti-spam tab\nDouble Click on IP block list providers\nClick on the providers tab and click add\nFor 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.