Earlier this month the .NET Blog announced that the .NET Framework 4.7 has reached general availability. Do not install this update on your Exchange servers.

Refer to the Exchange Server Supportability Matrix which provides a central source for Microsoft Exchange administrators to easily locate information about the level of support available for any configuration or required component for supported versions of Microsoft Exchange. At this time no versions of Exchange Server support .NET 4.7, although this is subject to change with future cumulative updates. Exchange Server runs on .NET assemblies and changing to an unsupported version may have dire consequences.

http://www.expta.com/2017/05/do-not-install-net-framework-47-on.html