Port 25, which is used by SMTP instance 'Default EXCHANGEFRONT', did not respond on server 0000

I should add, we have a 2003 exchange server we just put behind a firewall today, and installed this CAS to be out front as a CAS/front end server.  But we can't recieve any mail as of yet.

My CAS is on a DMZ, should it be or no?  If not then where?  I was under the impression that the point of a CAS was so you could put it outside your network?  Or at least firewall your backend?

ahhh crap, just read up, CAS isn't supported on a DMZ.  Well I was sure misinformed....crap..  Ok, so we want to protect our exchange 2003 server, how do we keep it behind a good firewall?  Since CAS on DMZ it out of the question.?

will Microsoft ISA work on the DMZ with only exchange 2003 on the inside?  Or do I still need CAS?

or forefront exchange security?

Should I use ISA?  Or forefront security for exchange? I'm thinking #2

Or can I just use the Edge transport server that's built into exchange 2007?

Edge doesn't do OWA etc, it is only for SMTP traffic.
Forefront is an AV product, I don't think it is standalone, so would need a host, like Edge.

-M

We decided to migrate our 2003 exchange to 2007 so I can install the hub transport, and then installed the edge server on the dmz to connect to it.

I found that once I removed the IPv6 networks from my Receive connectors (All of them) It worked just fine.  My issue was that I was in a Windows 2003 64-bit server and did not need the IPv6 addresses.