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As always, test these updates in a lab first! I recommend checking out this 7-part guide on configuring Exchange in your lab. It doesn’t take much to get one going.
The updates are as follows:

Exchange 2019 Cumulative Update 4 (VLSC)| KB4522149

Exchange 2016 Cumulative Update 15 | KB4522150 | UM Language Pack
Exchange 2010 support extended
Back in September, the Exchange Team announced that is was extending support for Exchange 2010 by nine months. Exchange 2010 now shares the same end-of-life date as Office 2010 and SharePoint 2010, which is October 13th, 2020.
While this extension allows for a little more breathing room, it does not extend support for Windows Server 2008 R2, which is the underlying operating system for many Exchange 2010 installations. Server 2008 R2 will still go end of life on January 14th, 2020.
The Exchange Team has provided this extension to allow companies more time to migrate to a newer email platform, such as Office 365, or, Exchange 2016.
Unfortunately, there is no direct path to Exchange 2019 from 2010. If you do plan to stay on-prem, you will need to migrate to either 2013 or 2016 (I’d recommend 2016 as 2013 is now in extended support). From there you can migrate to 2019.
For more information on migrating from Exchange 2010 to 2016, check out this recent blog article from the Exchange Team: Exchange On-Premises Best Practices for Migrations from 2010 to 2016
So, what’s new in these Cumulative Updates?
In this series of cumulative updates, Microsoft has resolved a number of security and non-security issues. You can read more about those in KBs 4522149 and 4522150.
Most notably this fixes an issue I had run into myself in both Exchange 2016 CU13 and CU14. The issue was after running the Hybrid Configuration Wizard you could no longer modify the Outbound to Office 365 send connector if your source servers were Edge Transport servers.
Attempting any modifications to the send connector would result in the errors: Error 0x5 (Access is denied) from cli_GetCertificate or Error 0x6ba (The RPC server is unavailable) from cli_GetCertificate. This error was caused because the Exchange organization was attempting to access the certificates on the Edge Transport servers. I can confirm CU15 resolved this error for me.

Note: Error 0x5 (Access is denied) from cli_GetCertificate was also reported in Exchange 2019 CU2 and CU3. It has been resolved in CU4.
[Read more…] about Exchange December 2019 Updates