The Exchange Team released the quarterly Cumulative Updates for Exchange Server 2019 as well as Exchange 2016. One significant change with these updates is the requirement for .NET Framework 4.8, as announced earlier. Also, Exchange 2019 CU4 comes with an updated Exchange calculator. Links to the updates as well as a description of changes and fixes are described below.

Version	Build	KB	Download	UMLP	Schema
Exchange 2019 CU4	15.2.529.5	KB4522149	VLSC		N
Exchange 2016 CU15	15.1.1913.5	KB4522150	Download	UMLP	N

Exchange 2019 CU4 fixes:

• 4528696 Exchange PowerShell cmdlets take longer time to run in Exchange Server 2019
• 4528695 Event ID 4009 when using SubjectOrBodyMatchesPatterns on Edge server in Exchange Server 2019
• 4528694 Can’t open .ics file in Outlook on the web in Exchange Server 2019
• 4528692 “A parameter was specified that isn’t valid” error when creating transport rule in Exchange Server 2019
• 4523519 Set-SendConnector doesn’t work for Exchange Server in hybrid scenarios with Edge Server installed
• 4528688 Only one recipient shows when saving draft by using Exchange ActiveSync version 16.0 in Exchange Server 2019
• 4528693 Get-CalendarDiagnosticLog is proxied for queries within the same forest in Exchange Server 2019
• 4528687 NotificationClient logs aren’t purged and consume lots of disk in Exchange Server 2019
• 4528689 Outlook on the web shows MailTip when recipients equal the large audience size in Exchange Server 2019
• 4528690 Can’t move or delete folder in Outlook online mode if the destination has a folder with the same name in Exchange Server 2019
• 4532744 System.ArgumentNullException when you use Set-user to assign block legacy auth policy in Exchange Server 2019
• 4532747 Address list separation not working for a user without a mailbox in Exchange Server 2019
• 4523171 Description of the security update for Microsoft Exchange Server 2019, 2016, and 2013: November 12, 2019

Exchange 2016 CU15 fixes:

• 4515256 “The function cannot be performed…” error when you send a message that’s open for a long time in Exchange Server 2016
• 4528693 Get-CalendarDiagnosticLog is proxied for queries within the same forest in Exchange Server 2016
• 4523519 Set-SendConnector doesn’t work for Exchange Server in hybrid scenarios with Edge Server installed
• 4528690 Can’t move or delete folder in Outlook online mode if the destination has a folder with the same name in Exchange Server 2016
• 4528687 NotificationClient logs aren’t purged and consume lots of disk in Exchange Server 2016
• 4528689 Outlook on the web shows MailTip when recipients equal the large audience size in Exchange Server 2016
• 4528688 Only one recipient shows when saving draft by using Exchange ActiveSync version 16.0 in Exchange Server 2016
• 4528695 Event ID 4009 when using SubjectOrBodyMatchesPatterns on Edge server in Exchange Server 2016
• 4528694 Can’t open .ics file in Outlook on the web in Exchange Server 2016
• 4528692 “A parameter was specified that isn’t valid” error when creating transport rule in Exchange Server 2016
• 4515257 Hash mismatch is reported for Exchange DLLs in the bin directory of Exchange Server 2016
• 4528696 Exchange PowerShell cmdlets take longer time to run in Exchange Server 2016
• 4532747 Address list separation not working for a user without a mailbox in Exchange Server 2016
• 4523171 Description of the security update for Microsoft Exchange Server 2019, 2016, and 2013: November 12, 2019

Notes:

• These Cumulative Updates do not contain schema changes compared to their previous Cumulative Update.
• When upgrading from an n-2 or earlier version of Exchange, or an early version of the .NET Framework, consult Upgrade Paths for CU’s & .NET.
• Don’t forget to put the Exchange server in maintenance mode prior to updating. Regardless, setup will put the server in server-wide offline mode post-analysis, before making actual changes.
• When using Exchange hybrid deployments or Exchange Online Archiving (EOA), you are required to delay installing at most one version (n-1).
• If you want to speed up the update process for systems without internet access, you can follow the procedure described here to disable publisher’s certificate revocation checking.
• Cumulative Updates can be installed directly; no need to install RTM prior to installing Cumulative Updates.
• Once installed, you can’t uninstall a Cumulative Update nor any of the installed Exchange server roles.
• The order of installation shouldn’t matter with the “every server is an island” concept, yet recommended is to upgrade internet-facing, non-internet-facing servers first, followed by Edge Transports.

Caution:

As for any update, I recommend to thoroughly test updates in a test environment prior to implementing them in production. When you lack such facilities, hold out a few days and monitor the comments on the original publication or forums for any issues.