Today we are announcing the availability of quarterly servicing cumulative updates for Exchange Server 2016 and 2019. These updates include fixes for customer reported issues as well as all previously released security updates.
This quarterly Exchange release includes an important update to the Exchange 2019 Sizing Calculator. We've made improvements to the logic to detect whether a design is bound by mailbox size (capacity) or throughput (IOPs) which affects the maximum number of mailboxes a database will support. Previous versions of the calculator produced incorrect results in some situations.
The Exchange team highly recommends using calculator version 10.4, included with the March 2020 quarterly CU release, to size Exchange Server 2019 deployments.
MCDB Configuration Issues
Cumulative Update 5 for Exchange Server 2019 also fixes an issue that can happen when you use the Manage-MetaCacheDatabase.ps1 script to enable MetaCacheDatabase (MCDB).
This issue occurred because of a change in behavior in Windows Server 2019 that caused Get-Disk to return all uninitialized discs within the Database Availability Group (DAG) or cluster. The script then incorrectly tried to format an SSD on another DAG member. We documented a workaround for CU4 here, but we’ve fixed it in CU5.
Online Mode Search Issues
Cumulative Update 5 for Exchange Server 2019 is also required to fix a known issue with partial word searches when the client is using Outlook in online mode.
The KB articles that describe the fixes in each release and product downloads are available as follows:
Microsoft recommends all customers test the deployment of any update in their lab environment to determine the proper installation process for your production environment. For information on extending the schema and configuring Active Directory, please review the appropriate documentation.
Also, to prevent installation issues you should ensure that the Windows PowerShell Script Execution Policy is set to “Unrestricted” on the server being upgraded or installed. To verify the policy settings, run the Get-ExecutionPolicy cmdlet from PowerShell on the machine being upgraded. If the policies are NOT set to Unrestricted you should use the resolution steps in this article to adjust the settings.
Reminder: Customers in hybrid deployments where Exchange is deployed on-premises and in the cloud, or who are using Exchange Online Archiving (EOA) with their on-premises Exchange deployment are required to deploy the currently supported cumulative update for the product version in use, e.g., 2013 Cumulative Update 23; 2016 Cumulative Update 16 or 15; 2019 Cumulative Update 5 or 4.