Certain users not recognizing alternate aliases

Not sure if anyone has had this issue. Having a problem where there are certain users within our mail system that when emails are sent from outside the company to their internet address within their person document it works fine but when you try to send to any domain within the alternate internet domains within the Global Domain document you get a ‘user not found in domino directory’ error message.

The domain I am trying to get working works fine with me and with others. It only seems to happen to certain people.

Anyone got any ideas?