Is it possible to host child domain user mailboxes in a Exchange 2010 box sitting inside Parent domain? For example, I have this Exchange 2010 MBX server as MBX1.contoso.local, can it host user mailboxes in NZ.contoso.local domain?

Hi aha_tom, From your description, I understand that you want the child domain user can use the mailbox in the parent domain, please correct me if I misunderstand the problem. For this issue, you can use linked mailbox to achieve the goal. Here are some related documents for you: Deploy Exchange 2010 in an Exchange Resource Forest Topology http://technet.microsoft.com/en-us/library/aa998031.aspx Create a Linked Mailbox http://technet.microsoft.com/en-us/library/bb123524.aspx Deploying an Exchange Resource Forest (Part 1) http://www.msexchange.org/articles_tutorials/exchange-server-2007/planning-architecture/deploying-exchange-resource-forest-part1.html Thanks, EvanPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.