You might have face this error message when doing Exchange 2007 to Exchange 2010 transition.
” A duplicated mailbox was found due to problem during a Move Mailbox procedure. The duplicate mailbox has been deleted.”
To check if there is a duplicate mailbox, please run the following Exchange cmdlet against the source and target mailbox database:
Clean-MailboxDatabase -Identity “<Exchange2010Server>\<StorageGroup>\<SourceorTargetMailboxDatabase>”
After clean up the database on each mailbox databse, we need go to Exchange Management Console -> Recipient Configuration -> Disconnected Mailbox to check the duplicate mailbox.
Move the mailbox from Exchange 2010 console instead of Exchange 2007. It should move the mailbox successfuly.