If you are running Exchange 2019 in your environment, including as part of an Exchange Hybrid setup, then you should be running the latest Exchange 2019 CU14 update. 

Exchange 2019 CU14 provides a number of important updates to Exchange 2019.   You can download it here. 

https://www.microsoft.com/en-us/download/details.aspx?id=105878

Exchange 2019 CU14 Extended Protection Feature

For Exchange 2019 CU14, the Extended Protection feature is enabled by default when installing within the GUI.   We recommend to consider installing Exchange 2019 CU14 via the Exchange Management Shell only. And to consider disabling Extended Protection via the supported parameters.   Warning – Extended Protection can impact some Exchange Hybrid installations. 

https://learn.microsoft.com/en-us/exchange/plan-and-deploy/post-installation-tasks/security-best-practices/exchange-extended-protection?view=exchserver-2019

My recommendation here is to install Exchange 2019 CU14 without Extended Protection initially. But to get the other important updates.  And then to test Exchange 2019 CU14 with Extended Protection in a lab environment fist. And to read the Microsoft warnings around Extended Protection very carefully – it does provide elevated protection against man in the middle attacks.  

Customers running Classic Exchange Hybrid then it should not affect you – only Modern Hybrid is affected.  SSL Offloading is not supported, nor are all Public Folder scenarios – testing is required.  Other applications or integrations that may be affected negatively by adopting Extended Protection.

There is an Extended Protection checker script provided by Microsoft that can be used to check your environment for compatibility, and to provide a rollback if needed. 

https://aka.ms/ExchangeHealthChecker

Exchange 2019 CU14 SU3 V2

Microsoft provided Exchange 2019 CU14 back in March 2024, and there have been some other Service Updates since then – so please look at applying the latest valid one – see below. Updates are cumulative.

Security Update For Exchange Server 2019 CU14 SU3 V2 (KB5049233) 

https://www.microsoft.com/en-us/download/details.aspx?id=106320

Make sure you use the CU14 SU3 V2 as this fixed a bug in the initial release of CU14 SU3.  We recommend you are always using the latest updates from Microsoft for your Exchange 2019 servers, as it is likely that these are internet facing in some capacity. 

Exchange 2019 CU14 Expert Consulting

If you need consulting help with applying the latest Exchange 2019 CU14 update with Extended Protection, then please reach out to me via the Contact Us form in this website.