How to purge a soft deleted mailbox in Office 365
We have recently changed the way, removing an Office 365 user with attached mailbox, behaves.
If we deleted an active user while he was still licensed, his mailbox would go into a “soft deleted” state and could have been recovered, just by restoring the user.
If we also purged the MsolUser from Office 365 with “Remove-MsolUser -ObjectID <guid of soft deleted user> -RemoveFromRecycleBin -Force”, his soft deleted mailbox would also be purged, unless it was specifically put on Litigation Hold or In-Place Hold.
The first situation remains the same, as in if we soft delete the user account, while he still has a license assigned, his mailbox will go into a soft deleted state.
The change however, is that if we purge the user account, the mailbox is no longer purged with it, instead it will remain in a soft deleted state, regardless if previously it was put on Litigation Hold/In-Place hold or not.
Read more at source: https://blogs.technet.microsoft.com/exovoice/2016/05/24/how-to-purge-a-soft-deleted-mailbox-in-office-365/