If you enable an In-Place Hold for a mailbox, some items are not deleted after the In-Place Hold expires. This issue causes a large number of items to be held unnecessarily in the DiscoveryHold folder of the mailbox.
This issue occurs because multiple items are incorrectly tagged as "partially processed" by the Exchange search component. Partially processed items are not purged by an In-Place Hold.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.