Can’t receive mail sent to ip address

While trying to remove my server from a blacklist site, I get the error message listed below. postmaster@domainname.com works fine, but postmaster@ipaddress does not. How do I “fix” my Exchange 2000/ Win2000 server? :

Your server seems to believe it needs to relay for local addresses.
This does NOT mean that it is closed to relaying; just that it is
broken and does not accept and deliver local mail, albeit with a
confusing error message. Please fix it and test addresses from OUTSIDE
before requesting removal.

Result:

Recipient Report:

67.128.xx.xx does not like recipient.

Remote host said: 550 5.7.1 Unable to relay for
postmaster@67.128.xx.xx

Message Report:

Giving up on 67.128.xx.xx.