Just a reminder, the Exchange team blog site posted an important message about NOT installing .NET 4.6.1 just yet. The Exchange product group is working on supporting this upgrade, but that option is NOT yet currently available.
There are some installation issues with how Exchange and the core Windows Operating System interact and how features like .NET are upgraded. It is this matching of code and how the Exchange product is installed that is currently being resolved.
.NET 4.6.1 brings several new features with specific information that needs to be tested with Exchange before there is a fully supported path for upgrading. As always, visit the Exchange Supportability Matrix for a full list of what is and what is not supported. Remember, if an item is NOT listed on the matrix, then it is NOT supported. This once again will be important for when Windows Server 2016 is released. It will take the Exchange Product Group time to support the new server OS and for the Exchange Supportability Matrix to be updated. Do not assume if an item is not listed, it is supported.
Consequently, with this .NET release, you need to make sure that your Exchange servers are not automatically getting the update installed. You’ll also want to confirm any other .NET applications in your environment can support the upgrade or not. As always, you should test patches/upgrades in a lab or test environment before rolling those changes out into production.