A quick heads-up that when you are running Exchange Server 2013, you should not install or update to .NET Framework 4.6. This version of the .NET framework is not only not supported, it may also cause your Exchange 2013 server to stop functioning correctly.
When you have updated from a previous version, a suggested workaround is to uninstall .NET Framework 4.6. However, with all the dependencies on the .NET Framework by Exchange Server, it maybe preferred, when you did install version .NET Framework 4.6, to migrate contents, i.e. mailboxes etc., to a new Exchange 2013 server, and decommission the one you installed .NET 4.6.
More information can be found in KB3095369.
EighTwOne (821) 
Hi Michel, could you tell me please what book(s) we need to read to be prepared update from Exchange 2010 to Exchange 2013 ? Thank you very much in advance for you answer!
LikeLike
There are now many good books on the market. Me and a fellow Exchange MVP wrote a book for Exchange 2013 SP1 (but is also valid for later Cumulative Updates), which contains information on upgrading from previous versions. You can find the book on Amazon here: http://bit.ly/ProEx2013SP1
LikeLike
Thats a pretty big issue…
LikeLike
Thank you very much for my previous question and your book Michel!
LeŠµ me ask (last time), if we decide upgrade, what sequence will be right. We have MS Exchange 2010 which is installed on OS Windows Server 2008:
1. Upgrade OS Windows Server 2008 > 2012
2. Upgrade MS Exchange 2010 > 2013
or
1. Upgrade MS Exchange 2010 > 2013
2. Upgrade OS Windows Server 2008 > 2012
Thanks!
LikeLike
Depends. In any way, you need to deploy a new configuration and migrate, there are no in-place scenarios.
LikeLike
Sorry I forget to point, we have a cluster on MS Exchange 2010
LikeLike
This happened to us idk if we installed exchange 2013 on-top of 4.6 or windows update installed 4.6 on-top of exchange 2013 however either way Microsoft should disable or warn you about this during. however when i removed 4.6 all hell broke lose and nothing worked has to reinstall 4.6 any ideas on the best was to remove 4.6 without a 2nd exchange server,
LikeLike