Unlike previous versions of Microsoft Exchange Server, Exchange 2010 not only has Offline Mailbox Move but Online Mailbox Move too. So what is meant by Online & Offline Mailbox Move. It is all about End User experience, if during the move, Mailbox is not available (or offline) then it is Offline Mailbox Move and vice-versa
The User Experience depends upon the Source and Target versions of Exchange, which can be summarized as below:
Online Mailbox Move: As can be seen in above table, when Mailbox is moved from Exchange 2010 to Exchange 2010 or from Exchange 2007 SP2 (and above) to Exchange 2010, the move is Online. What happens is that Mailbox Replication Service, starts synchronizing the source and target mailbox, and until the final step of cutover is performed the Mailbox is Online. Only for a limited period when updates to the user attributes in active directory are being made, the Mailbox is locked or unavailable to user. In this case the user needs to Logout of Outlook and Log back in to automatically update the profile with new server/database information.
Offline Mailbox Move: In this case, as can be seen from above table, the mailbox becomes offline the moment the mailbox move is initiated and the Mailbox is Offline, for the entire duration of the move.
Unlike Exchange 2007, there is no more Move-Mailbox cmdlet in Exchange 2010, rather there are a set of cmdlets available for the Mailbox Move, as follows
We will discuss these in detail soon.