Reply Addresses in Exchange

This might be an easy one for you guys and I think I already know the answer, but it is worth a shot. I am running Exchange 5.5 on Nt 4.0. I have 4 email domains setup and receiving on the server successfully. Some employees are receiving email at all 4 domain addresses. Is there a way for exchange to reply by the same domain address it was sent to instead of replying by the default domain address (which could have been another domain address)? Other options are welcome.