Exchange Server 2000 & My DMZ Setup

Hi every body ….

I have a DMZ network setup where I need to
keep my Exchange 2000 Server within the
protected segment ( private LAN ) and have
a corresponding SMTP relay server on the DMZ
segment ( Public LAN ) .
Any idea about that ?
I have the following DNS setup :

A Public DNS Server within the DMZ
A Private DNS Server within the Private LAN.

Thanks for every one out there.