This update also includes new daylight saving time (DST) updates for Exchange Server 2013. For more information about DST, see Daylight Saving Time Help and Support Center.
Issues that this cumulative update fixes
This cumulative update fixes the issues that are described in the following Microsoft Knowledge Base articles:
4502131 "TLS negotiation failed with error UnknownCredentials" error after updating TLSCertificateName on Office 365 send connector in Exchange Server 2013 hybrid environment
4503028 Description of the security update for Microsoft Exchange Server 2013 and 2010: June 11, 2019
Get Cumulative Update 23 for Exchange Server 2013
You can use the Cumulative Update 23 package to run a new installation of Exchange Server 2013 or to upgrade an existing Exchange Server 2013 installation to Cumulative Update 23.
You do not have to install any previously released Exchange Server 2013 cumulative updates or service packs that were released before Cumulative Update 23 before you install Cumulative Update 23.