Accessing Exchange through a two way trust

Dan560 used Ask the Experts™

I have two company's that are under the same parent company. Company 1 has an Exchange server and company 2 doesn't use exchange. If I create a two way trust between company 1 and company 2 would it be possible to create mailboxes for company 2 that are tied into their AD account?
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PowerShell Developer
Top Expert 2010

Hey again :)

You will need to do the following for each user from Company 2:

1. Create an account for the user in Company 1 domain with a mailbox
2. Modify the Security on that mailbox, add the account from Company 2 to the list with "Full Mailbox Access" and "Associated External Account"
3. Disable the user account for the mailbox in Company 1. The account from Company 2 will still be able to use the mailbox.

You won't be able to mail enable accounts in Company 2 I'm afraid, hence the need for account duplication in Company 1.


Yes, this is called a "resource forest" scenario where the user accounts are in one forest and the mailboxes are in another. Here's an article on how to do it for Exchange 2007: If you need to find this for Exchagne 2003, just Google "resource forest" and you'll find similar instructions.

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