I need some info regarding installing the ISA Server with 3 NICs and implementing the DMZ as a MailRelay zone. In the way I would like to prevent any access to the MS Exchange Server inside my Internal Network. Any idea how to implement this?
Put the realay in the DMZ, and then put the mail server on the internal network. Then, publish the internal mail server and allow access only to the IP address of the server on the DMZ. In this way, you prevent any machine that is not the relay from accessing the internal server.