Cannot receive emails from specific domain - Microsoft Exchange

In news:eIb4uASNHHA.4848@TK2MSFTNGP04.phx.gbl,
Salvatore Cennimo <scennimo@optonline.net> typed:
> We are running windows 2000 server with Exchange 2000. We receive
> plenty of emails from this one domain. We have been getting these
> emails for the past 6 months or so with no issues. All of a sudden,
> we are not getting these emails and that is a big problem for us. I
> have not made any changes to our network or to exchange. I am able to
> send emails to that domain, but when they reply we do not get them.
> They also are not getting any undeliverable messages back. This issue
> looks like it just started around the 3rd of this year. For emails we
> are also using 2 domain names for our emails. Company name change. We
> have not used the old email domain name with this company. When they
> use the old email domain name, we receive the email. When they use
> the new one, we do not and this is the one they have been using for 6
> months plus with no issues. I have check a few things, but it does
> not seem to be an issue on my end. This is the only problem that we
> seem to have and only with them. Otherwise we are getting all our
> emails from anybody else just fine. Sure would appreciate any help
> with this one. Thanks

Do you have NDRs enabled?
You might need to crank up your SMTP logging.