Consider the following scenario:
You turn off the Require SSL setting for the Messaging Application Programming Interface (MAPI) virtual directory in Microsoft Exchange Server 2016.
You apply a cumulative update of Exchange Server 2016.
In this scenario, the Require SSL setting will be turned on. However, it's expected that the MAPI virtual directory maintain the settings. In addition, the other virtual directories don't have this issue.
This issue occurs because the Require SSL setting is reset by Exchange setup during the installation of cumulative updates or service packs of Exchange Server 2016.
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.