Mails not being received in one partcular domain

Hi,

We have installed a domino server which uses a Relay Host to send mails to external domains.

All the mails have so far been transmitted successfully to all Internet domains, except one domain. The users in that domain are not receiving any mails from the particular server. The name of the local domino server is abc\domino1 and the domain on which the mails are not being received is domino1.com. Is it likely that the users belonging to the domain domino1.com are being checked in the local Lotus Domino Server?

Is there a way this can be avoided so that the Domino server does not check for the users of the external domain “domino1.com” in its Internal address book?