Microsoft has delayed the release of the June 2021 cumulative updates for Exchange Server for two weeks to integrate the Windows Antimalware Scan interface (AMSI). The change will allow Exchange 2016 and Exchange 2019 servers running on Windows Server 2016 or later to integrate antimalware engines to check HTTP requests for potential problems. If ever there was good reason to delay an update, this is it.
Microsoft has released new cumulative updates for Exchange Server 2016, Exchange Server 2013, and Exchange Server 2010 SP3 in June 2018.
I strongly recommend you keep an archive copy of every Exchange Server installer, service pack, update rollup, and cumulative update in case of a support or recovery scenario that requires it.
Exchange Server 2013 has reached the end of mainstream support and is now in extended support, with the upcoming Cumulative Update 21 planned to be the last CU released.
Microsoft has released new cumulative updates for Exchange Server 2016, 2013, and 2010 in March 2018.