Exchange 2003 Config w/Dynamic DNS

I’m new to the 2003 server/exchange platforms, and i’m wondering how i can go about configuring exchange 2003 to work using Dynamic DNS. I have already updated my schema with forestprep and have run domain prep, and have installed exchange 2003 successfully. I have set up a Domain name with a dynamic dns service and have created an mx record with them to point to my external ip. On the flip site i have my mail server sitting in a DMZ and have set up forwarding from the firewall for ports 25,110. I’m not sure if the only thing left to do is set up a recipient policy for my domain name..

Please help if possible or point me in the right direction.

Thanks
Jay Stants