Microsoft Exchange 2010 SP 2 stop working with .NET Framework 4.5, email stop working.
By logging in the Exchange Management Console, we will notice that the database is unmounted and you are unable to mount it back on.
To resolve this issue with Microsoft Exchange 2010, you need to update it with the Microsoft Exchange 2010 service pack 3. After which it should start working for you.
Note: Did a further testing on Microsoft Exchange 2010 with SP 1 seems like this issue does not exist.
Not very sure why this is happening and this is the quick fix I figured.