If you have never updated your Exchange 2013 you can came across of one installation error caused by interim update KB2874216
When you try install new er verso you will be greats by error message similar to this:
Unable to install because a previous Interim Update for Exchange Server 2013 Cumulative Update 1 has been installed. Please use Add/Remove Programs to uninstall the Interim Update before running this setup again
If you try to uninstall it it will ask for exchangeserver.msi form CU1. Most likely you do not have this, because it is 3+ Years old and there is no way to find it on Microsoft site also.
The solution is to delete the following key in the registry:
deleted: HKLM\Software\Microsoft\ExchangeServer\V15\Setup\Interim Update 284216 from Registry.
restart the server and try again to install newer update.