IIS 4 SMTP Relay and OWA on DMZ connecting to Ex 5.5

[Ryan]

I have been tasked with implementing a new network design. Currently our
network has an Exchange 5.5 SP with OWA on top of it. We need to
implement a network with a DMZ. On this DMZ I need to place IIS SMTP
Relay and OWA.

I have read through the newsgroup and found suggestions that say leave it
as is, but management won't let that fly. I also searched technet and
found an extremely un-informative article Q230235. I also found the
www.swinc.com Exchange 5.5 FAQ, but that refers to M$ Proxy.

We currently re-route email for 3 domains. Could someone please break it
down Barney style for me on what needs to go in what fields for both IIS
and Ex.

Thanks in advance,
Ryan