I have recently taken over and am managing a network where the exchange server (2010) is hosting email for multiple companies. All of these companies are affiliated with the main company in one way or another. Here is the issue I am having. We have just recently started up a new company and it is imperative that from the outside these companies look separate and that the information remains separate. I know that I can set up the new domain as an authoritative accepted domain in exchange as that is the way all of the other companies have been set up.
Handling the of the permissions is easy enough for files, databases ect... but here is where my issue is. Lets say the main company is abc.com and the new start up is xyz.com. If I create a domain account and inbox with with abc.com and set up an alias for him at xyz.com that leaves an email address (abc.com) that people could technically send mail to and even though all of the data would be completely separate it's something that cannot happen.
It is possible to remove the abc.com email address from his account and just leave the xyz.com
If the above is not possible then does anyone have any suggestions that would keep costs down yet provide the separation that is required.