Our Exchange5.5 server currently configured to our main domain name which I will name it as chandrakalum.com, so that it creates e mail addresses like : recipient@xxxxxxxxxxxxxxxx . We are having another unix mail server for our internal staff and it is configured as a sub domain like, staff.chandrakalum.com in which the e mail address is like : recipient@xxxxxxxxxxxxxxxxxxxxxx Now we are considering the possibility of shifting our unix mail server also to existing Exchange Server. Can we have two mail server domains( actually a main domain and sub domain) within Exchange 5.5 ? (We can?t change e mail addresses of users in both servers. ) Appreciate if someone guide us ? Thanks in advance?