Client has a root domain and several child domains.  Exchange 2007 servers are installed in the root domain.  The server roles are distributed - MB, HT and CAS.   Some child domains have a single Exchange 2007 server with combined roles and some child domains have a single Exchange 2010 server with combined roles.  All Exchange servers in all domains are part of the same Exchange Organization.  A migration of mailboxes on root domain MB servers only to Office 365 is planned.  A hybrid server Exchange 2013 server will be deployed in the root domain to support the migration.   To support this, which child domains should setup.exe /preparedomain:<fqdn> be run against?  

Thanks in advance.

Dale

dale.newhart@rbaconsulting.com

Is there any reason you don't want to specify /PrepareAllDomains?

Child domains are administered by other organizations in the business.    If a child domain does not have to be prepared because they will not have an Exchange 2013 server, then the client wants only to run PrepareDomain on the root domain.

The prep is both for servers and for recipient objects in the domain, so I would strongly recommend doing it so it doesn't come back to bite you in the ass later.