HiI will be migrating my current domain to allow for our new company divisions and moving to a Root domain with sub domain design. Our main HQ will have the installed: Root DC Sub domain DCs for each division Install exchange 2007in the root domain Division offices: Sub domain DC for that division Possibly local exchange server I will install exchange in the root domain, my question is what if i wanted to install an exchange server in a branch office for local mailbox access at those sites to reduce traffic across the WAN... would i need a DC for the root domain also at the branch office? Are there any guides for this scenario (all guides i have seen so far are for single domains with multiple Active directory sites). Many thanks, Chris

A branch office should be a separate AD site, so the documentation you found should still apply. You need a DC for every site. Also, understand that if you have a branch mailbox server, you also need a client access server and hub transport server in that site. These can all reside on the same box though. Are the branch offices also the same as the sub-domain "division" offices? If so, this will get complicated and fast. I would consider using v-lans if you have two domains sitting on the same wire. Just my .02 cents, but I would fight, kicking and screaming before someone made me create different AD domains for separate business divisions. This complicates the structure, and there is really nothing you can do with multiple domains in a forest that you can't do with proper single AD domain/site/ou design.

Hi Mike, i did mean child domains sitting in a one tree forest rather than lots of single domains in a forest, does that change anything? Many Thanks

Dear customer: In each domain, including child domains, where you plan to install Exchange 2007, you must have at least one domain controller that is running Windows Server 2003 SP1 or a later version. You must have at least one global catalog server in every Active Directory directory service site where you plan to install Exchange 2007.Additionally, in order to ensure mail flow work normal, you must install CAS, Mailbox and HUB transport server role at each AD site. For more information about how to implement large Exchange server 2007 organization, please refer to the following documents: Deploying a Large Exchange Server 2007 Organization http://www.microsoft.com/downloads/details.aspx?FamilyID=8ECE7461-1D43-49A9-BACB-DEDC0AD3AC9F&displaylang=en I hope the information above can address your concerns. If anything is unclear, please feel free to let us know. Rock Wang - MSFT

Thanks for the reply, i note on the diagram for fabrikam.com organisation exchange is deployed in the us.fabrikam.com child domain... what if the eu.fabrikam.com domain wanted to use exchange also? Would it not be better to install exchange in the root domain? Many thanks

Dear customer: Thanks for your reply. All domains in a forest have transitive trusts between them, and as long as the Domain Name System (DNS) is working correctly for all domains in the forest, this configuration of users and servers should function normally. So the eu.fabrikam.com domain can also use the Exchange that installed in us.fabrikam.com child domain. Of course, you can also install other Exchange servers in the eu.fabrikam.com child domain. In this article, the root or parent domain is deployed primarily to provide a namespace for the forest. An equally important function is to prevent the proliferation of domains and expansion of the forest. Adding domains to a forest requires administrative access to the root domain, and typically very few personnel have administrative access to the root domain. I hope the information above can address your concerns. If anything is unclear, please feel free to let us know. Rock Wang - MSFT