Cumulative Update 23 for Exchange Server 2016: Fixes and Features
How to Download CU23 for Exchange Server 2016
If you are running Microsoft Exchange Server 2016 in your organization, you might want to know how to download and install the latest cumulative update (CU) for it. In this article, we will explain what CU23 for Exchange Server 2016 is, why you should install it, and how to download and install it. We will also show you how to verify the installation of CU23 and provide some frequently asked questions (FAQs) at the end.
What is CU23 for Exchange Server 2016?
Cumulative Update 23 (CU23) for Microsoft Exchange Server 2016 was released on April 20, 2022. It includes fixes for nonsecurity issues and all previously released fixes for security and nonsecurity issues. These fixes will also be included in later cumulative updates for Exchange Server 2016. This update also includes new daylight saving time (DST) updates for Exchange Server 2016.
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Features and fixes in CU23
Some of the new features and fixes that are included in CU23 are:
To prevent misuse of UNC paths by attackers, parameters that take UNC paths as inputs will no longer be usable in Exchange Server PowerShell cmdlets or the Exchange Admin Center.
The MSExchangeServiceHost service crashes repeatedly and Event ID 4999 is logged in the Windows Application event log.
The Get-MailboxDatabaseCopyStatus cmdlet from an Exchange Server 2013 server fails against databases on Exchange Server 2019 and 2016 servers and returns Error 0xe0434352 from RpccGetCopyStatusEx4.
Checking the Exchange Server 2019 or 2016 database status from the Exchange admin center (EAC) might fail and return an "HTTP 500" or "Your request couldn't be completed. Please try again in a few minutes" error message.
The UM Voicemail greetings function stops working and returns error "0xe0434352".
The Get-EmailAddressPolicy cmdlet fails and returns "Microsoft.Exchange.Diagnostics.BlockedDeserializeTypeException".
"Cannot Send Mail - Your mailbox is full" error when you use iPhone mail to send very large attachments.
"Migration user... can't be found" error when using Start-MigrationUser after batch migration fails.
You can't access OWA or ECP after installing the July 2021 security update.
External attendees see Send the Response Now although no response was requested in Exchange Server.
Email stuck in queue starting from "2022/1/1 00:01:00 UTC+0" on all Exchange on-premises servers.
Start-MigrationUser and Stop-MigrationUser are unavailable for on-premises Exchange Server 2019 and 2016.
Known issues in CU23
Some of the known issues that are not fixed in CU23 are:
The Get-MailboxStatistics cmdlet may report incorrect values for TotalDeletedItemSize property.
The Set-Mailbox cmdlet may fail when setting a mailbox quota value that is larger than Int32.MaxValue .
The Get-User cmdlet may return incorrect values for the RecipientTypeDetails property.
The New-MailboxExportRequest cmdlet may fail when exporting mailboxes to PST files on a network share.
The New-MailboxRepairRequest cmdlet may not work for mailboxes on a database that is part of a database availability group (DAG).
Why should you install CU23 for Exchange Server 2016?
Installing CU23 for Exchange Server 2016 is not mandatory, but it is highly recommended for several reasons. Here are some of the benefits and risks of updating or not updating your Exchange Server 2016.
Benefits of updating Exchange Server 2016
Some of the benefits of updating Exchange Server 2016 to CU23 are:
You can get the latest security fixes and patches that protect your Exchange Server 2016 from vulnerabilities and attacks.
You can get the latest features and enhancements that improve the performance, reliability, and functionality of your Exchange Server 2016.
You can get the latest compatibility and interoperability updates that ensure your Exchange Server 2016 works well with other Microsoft products and services.
You can get the latest support and documentation updates that help you troubleshoot and resolve any issues with your Exchange Server 2016.
You can stay in compliance with the Microsoft Lifecycle Policy that requires you to install the latest cumulative update to receive technical support and security updates.
Risks of not updating Exchange Server 2016
Some of the risks of not updating Exchange Server 2016 to CU23 are:
You may expose your Exchange Server 2016 to security threats and exploits that could compromise your data and network.
You may miss out on the new features and improvements that could enhance your user experience and productivity.
You may encounter compatibility and interoperability issues that could affect your communication and collaboration with other Microsoft products and services.
You may face support and documentation challenges that could hinder your ability to troubleshoot and resolve any issues with your Exchange Server 2016.
You may violate the Microsoft Lifecycle Policy that requires you to install the latest cumulative update to receive technical support and security updates.
How to download CU23 for Exchange Server 2016?
Now that you know what CU23 for Exchange Server 2016 is and why you should install it, let's see how you can download and install it. Before you proceed, make sure you meet the prerequisites and requirements for installing CU23.
Prerequisites and requirements for installing CU23
Before you download and install CU23 for Exchange Server 2016, you need to ensure that:
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Your Exchange Server 2016 is running at least CU8 or later. If not, you need to upgrade your Exchange Server 2016 to a supported cumulative update first.
Your Active Directory schema is updated to support CU23 for Exchange Server 2016. You can use the Setup.exe /PrepareSchema command to update the schema. You need to have Schema Admins permissions to do this.
Your Active Directory forest is prepared for CU23 for Exchange Server 2016. You can use the Setup.exe /PrepareAD command to prepare the forest. You need to have Enterprise Admins permissions to do this.
Your Active Directory domain is prepared for CU23 for Exchange Server 2016. You can use the Setup.exe /PrepareDomain command to prepare the domain. You need to have Domain Admins permissions to do this. Alternatively, you can use the Setup.exe /PrepareAllDomains command to prepare all domains in the forest. You need to have Enterprise Admins permissions to do this.
Your servers meet the minimum hardware and software requirements for running CU23 for Exchange Server 2016. For example, you need at least 30 GB of free disk space on the drive where you install Exchange, and at least 200 MB of free disk space on the system drive. You also need Windows Server 2012 R2 Standard or Datacenter, Windows Server 2016 Standard or Datacenter, or Windows Server 2019 Standard or Datacenter as the operating system .
Your servers have the latest Windows updates and security patches installed. You can use Windows Update or other methods to check and install the updates.
Your servers have the required roles and features installed. For example, you need the .NET Framework 4.8, the Visual C++ Redistributable