A quick command to determine where a mailbox has been moved during its lifetime. It is common for a mailbox to have been moved from database to database, and therefore at different points in time been backed up to different databases. When it comes to a need to restore a database, then you’ll need to know which database it was on at that time, because you don’t want to have to restore all of the databases!
The below command shows you the move history of a mailbox, you run it from the Microsoft Exchange PowerShell console.
(Get-MailboxStatistics "username" -IncludeMoveHistory).Movehistory | FT SourceDatabase, CompletionTimestamp