SMTP Gateway for Exchange 2003

Please help me!

I need to setup the SMTP Gateway for the Exchange 2003 with one server. But could not find any information for it. Could someone kindly tell me how to do it?

What I want is to put my Exchange in Internal network and allow only HTTPS from Internet. I want to put the SMTP Gateway in the DMZ for all the Mail will have to go throuht that Gateway.

Thank you very in advance.

Michael