A recent cumulative update for Exchange 2016 was intended to add support for Windows Server 2016. But, after numerous reported issues, Microsoft has acknowledged a problem exists. According to the release notes… If you attempt to run Microsoft Exchange 2016 CU3 on Windows Server 2016, you will experience errors in the IIS host process W3WP.exe. There is no workaround at this time. You should postpone deployment of Exchange 2016 CU3 on Windows Server 2016 until a supported fix is available. Once again, Microsoft’s testing of its own patches seems to have taken a backseat to accelerated release deadlines.