I have a client who is starting up a new business with very little cash. To help him, I have offered to host his e-mail on my Exchange Server. I am running an Windows network using Windows Server 2003 and Exchange Server 2003. He will have approximately 16 people who need e-mail. I want to setup and host his e-mail domain within my existing domain. I want his users to have only his domain e-mail addresses. I want to restrict his users to a custom address list for his company only. I have been reading about this for a few days via Google, etc and I am confused. Can some please point me in the right direction?