When migrating users from Exchange 2003 to Exchange 2010, you get to a point where you actually want to move all those Exchange 2003 mailboxes. When you have a decent environment and a lot of mailboxes are involved, you perhaps may want to move those mailboxes in a more phased, batch-oriented fashion.

If so, perhaps the following one-liner may come in handy, which is to be executed from the Exchange Management Shell:

Get-Mailbox -RecipientTypeDetails LegacyMailbox -ResultSize Unlimited | Where { ($_.MailboxMoveStatus -eq ‘None’) -and ( $_.WhenChanged -lt (Get-Date).AddDays(-1)) } | Select -First 100 | New-MoveRequest

I’ll talk you through the one-liner:

• We’ll start off by selecting all mailboxes using Get-Mailbox using an unlimited result size (defaults to 1,000). By selecting only “LegacyMailbox” using the RecipientTypeDetails parameter, we’ll only select the Exchange 2003 mailboxes;
• Next, we filter the those mailboxes on the following properties:
• MailboxMoveStatus. By selecting “None”, we get mailboxes not in the process of being moved;
• WhenChanged. We select mailboxes unaltered in the last 24 hours to accomodate for users currently accessing their mailbox (since it’s an offline move). For this purpose, we take the current timestamp (Get-Date) and subtract 1 day (by adding -1 day which is the same).
• Then  we select only the first N (the sample uses 100) mailboxes of the result (or lower if there are less mailboxes elegible so far);
• Finally we pipe that to New-MoveRequest. We don’t mention any Remote parameters so it’s a local move. Also, by omitting the target database, we let Exchange select an Exchange 2010 database.  This is done in a round-robin fashion (as you can see below) and does all the work for us like checking availability of the database as well the auto provisioning status of those databases or servers.

Now you can start or schedule this and check back in the morning on the results. When situation requires, you can start off using smaller batches increasing things depending on the results, ultimately leaving out the Select and date condition altogether.

And don’t forget to clean up those move requests afterwards.