[otrs] Mail address~

Hello all, Maybe someone will know what to do. We have M$ Exchange mail server. Not all mail users have external email address (they do not have smtp address). I do not know, how to setup OTRS, to be able to send those people email notification. Also what format use at entering email of such customer to OTRS, because it requires only addresses with @. Please help me - how to set that, this and the previous problem can break down whole my helpdesk project:(((( Thanks in advance Marek Drnak