Assume that you use an ActiveSync device for email synchronization in a Microsoft Exchange Server 2013 or Exchange Server 2016 environment. After you turn off the device overnight, you may experience synchronization issues for messages in the Read or Unread status.
This issue occurs because the sync state isn't initialized correctly for the first synchronization that's made in the next day by the device.
To fix this issue, install one of the following cumulative updates:
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.