I am running Exchange 2003 with a Front end and Back end server, all of which is behind a firewall which nat's to the outside. We would like to test an antispam solution which basically is a separate non-exchange box, also behind the firewall. Is there a way to point my outgoing email from exchange through this IP address. As my exchange servers have traditionall talked directly with any external email servers (through the firewall), I am now not sure how to implement this. The purpose of this is to allow the antispam solution the ability to whitelist/autoadd outgoing email addresses so that they aren't caught on the way back.