I have been asked some questions recently regarding the Cross-site mailbox moves using the native tools in Exchange 2003. I have found a very good explanation from Evan Dodds of what we do in general with Move Mailbox:

http://blogs.technet.com/exchange/archive/2005/02/15/373021.aspx

Some key points:

  • Users don’t have to be logged out of the mailbox during a mailbox move.
  • You should stop the ADC before doing a move mailbox in a mixed mode site or Routing Group.
  • You don’t have to stop the ADC for Cross-site moves however. This includes cross-site mixed mode as well.

Please read the above entry for more great information regarding Move Mailbox in general.