A site wanted to be able to relay mail from an internal process to both internal and external email addresses. These were plain SMTP messages generated by a host application. The internal messages were accepted if we put in a relay exception in the GWIA, but the external messages were rejected with a 550 error - "Relaying not allowed."
We were able to add the external user to a distribution list and send the mail successfully. We did this by creating an external user in an non groupwise domain, in an external post office. We gave the address of the external account we wanted the email set to, to the post office. This works for as many users as you need.
One thing the customer was not so crazy about was having the address show up in their address book. I'm not sure if they could have set the visibility of the user in the address book to domain only; my guess is it may not have worked, so long as the GWIA was in a different domain. We didn't do much in the way of testing on that point.
Groupwise 7.02 with hotfix on SLES 10
Disclaimer: As with everything else at Cool Solutions, this content is definitely not supported by Novell (so don't even think of calling Support if you try something and it blows up).
It was contributed by a community member and is published "as is." It seems to have worked for at least one person, and might work for you. But please be sure to test, test, test before you do anything drastic with it.