If you are still running Exchange 2013, don’t neglect your patching. I had not updated my lab servers in two (2) years and updated to the latest Cumulative Update (CU) and Security Update (SU) that is available. Patching ensures that you are secure with what has been closed in the updates. Below are some screenshots of the update process, you launch command prompt elevated and then navigate to the exe file and then run it.
Update process:
Once you click the Finish button, don’t forget to restart, you should be prompted but if not, restart so the DLL files etc. can update.
Hope it helps.