Use the Bulk Restore options to restore a user's entire mailbox, calendar, or set of tasks, notes, or journals. The Bulk Restore options compare your existing mailbox to the backup and restores missing items to their original location.
Note: This article only applies to email accounts that have the Office 365 backup add-on enabled. It is not applicable to any Office 365 account without this add on in place.
Note: The size of the data set that you're restoring, Office 365 availability and throttling affects how long a full restore takes to complete.