Challenge: Postmaster address problem

Hi,

Our exchange 2003 Enterprise edition server is in olddomain.com running on a Windows 2000 server using  Windows 2000 Active Directory. The postmaster email address is postmaster@olddomain.com.

We will be adding another new email address (@newdomain.com) to all users' email addresses and will be making it the primary address. Initiallly all internet emails destined for @olddomain.com and @newdomain.com will continue to work.

After changing postmaster@olddomain.com to postmaster@newdomain.com, NDR still
reports that it is coming from postmaster@olddomain.com.

Even after I deliberately deleted postmaster@olddomain.com email address, NDR still continue to report it is coming from
postmaster@olddomain.com.

I have the suspection that Exchange is getting the domain part of the email address from AD domain name (olddomain.com). We are not in the position to change the domain name at this stage. I tried to log a call with Microsoft support but I was told that it is not a break-fix so they can't help us.

I tried to seek advice from microsoft Exchange news group but to no avail.

Any exchange gurus out there can lend a hand is much appreciated

Thank you.

Joe