Help With Exchange 5.5 Changing Mail/DNS Domains

My mailserver and I outlasted our startup company "", bought by new company "". I have all employees setup with both and e-mail addresses and have both and registered with WorldCom. The A record is = X.X.X.X and mail inbound for points to

The mailserver is Exchange 5.5 SP4 on NT4SP5 and resides in the batman NT domain and in the Network Properties it says it's part of the DNS domain. All employees can successfully receive mail from the Internet to both their and addresses.

QUESTION (How do I pull it off)
I need to change the WorldCom DNS record to make this mailserver not dependent on the existence of publicly, for the future. To do this, I believe I simply need to swap the WorldCom DNS A record, so that the A record becomes and mail inbound for points to

Is there any reconfiguration I have to do on the Exchange Server side???????

I've asked around... some folks think that in the "Control Panel -> Network -> TCPIP Properties --> DNS Domain" that I need to change it from to but are not sure. Some seem to think that since I'm already receiving mail for both and, the DNS change with WorldCom should be invisible to the mail server.

Any advice is welcome. Thank you.

Who is Participating?
scdavisConnect With a Mentor Commented:
I have a similar config - a company that is transitioning 4 domain names.  I simply setup, like in your example.., with MX to (old config), with MX to (new config)

Changed the users primary SMTP addr's to be the one, and am patiently awaiting a few months before killing off the old name.  

The NT4 config dosen't really give a hoot what is setup for the local DNS suffix.  
bluezoo7Connect With a Mentor Commented:
Sounds simple enough. Changing the A record on the authorative DNS server (and making sure the MX records are correct) should solve the problem.

You may have to clear any DNS caching on servers or workstations that cache local entries (like W2K).

If you have the DNS suffix set on the mail server under the network properties you should change it to reflect the new domain.

There should be no other reconfiguration of the mail server needed.
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