Just a quick note of caution on KB4012178, this update may fail with 0x80070642 (User cancelled) if deployed using Configuration Manager.
The root cause is the installation timeout setting on the update:
The issue is that this update regenerates dlls (such as microsoft.exchange.rpc.dll). If the update runs out of time while the update is replacing these files, you may find yourself missing some dlls. This makes Exchange grumpy.
In my experience this update takes between 15 and 20 minutes to install, so setting the time limit to 30 minutes should be fairly safe. Otherwise, you can install the update manually, by downloading it from the update catalog and using the following command to install the update:
msiexec /p c:\temp\Exchange2013-KB4012178-x64-en.msp /lv* C:\windows\temp\KB4012178.log REBOOT=REALLYSUPPRESS MSIRESTARTMANAGERCONTROL=Disable
This avoids the timeout issue as well as gives you a nice verbose log in C:\Windows\Temp