In your organization you have Exchange 2007 or 2010 and you just installed Exchange 2013. In a remote office you have a mailbox on one of these servers and you move the mailbox to 2013. After completion you go and check that all is fine only to find mail queuing to that mailbox.
If you open up queue viewer you can see that the submission queue has mail in it and if you expand that queue and view the mails itself the following errors are logged:
- Message rerouted and delayed by store driver.
The mailbox is busy updating in Active Directory. As a result the mailbox is locked so mail cannot flow to that mailbox.
As soon as the update is complete the mail will be delivered and the queues will clear.
Hope it helps.