Two days before the Exchange Team Blog released a new article on Exchange Server comaptibility with the .NET Framework 4.7 ; Exchange Server is currently not supported with .NET Framework 4.7.
Be aware that you must manually disable the update to the new .NET Framework on our Exchange Servers for now.
The process to block the update is very similar to what you already know from earlier .NET Framework updates. Just navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP in your Registry. Add a REG_DWORD “BlockNetFramework47” and its value to 1.
Unfortunately .NET Framework 4.7 has been released in April, and you may already have it installed. Luckily you can easily go to the Control Panel → Installed Updates on your server and remove the Update for Microsoft Windows (KB3186539). This will fix it.
See https://blogs.technet.microsoft.com/exchange/2017/06/13/net-framework-4-7-and-exchange-server/ for the original announcement at the EHLO Blog.