Sign in with Microsoft
Sign in or create an account.
Select a different account.
You have multiple accounts
Choose the account you want to sign in with.

Cumulative Update 23 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

Known issues in this cumulative update

  • The MSExchangeServiceHost service crashes repeatedly and Event ID 4999 is logged in the Windows Application event log. For more information, see Exchange Service Host service fails after installing March 2022 security update.

  • Symptom:
    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.

    Run Get-MailboxDatabaseCopyStatus from an Exchange Server 2019 or 2016 server.

  • Symptom:
    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.

    Make sure that the admin mailbox is on an Exchange Server 2019 or 2016 server. If the admin account has no mailbox, make sure that all arbitration mailboxes (especially the “SystemMailbox{bb558c35-97f1-4cb9-8ff7-d53741dc928c}”) are on an Exchange  Server 2019 or 2016 server.

  • 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. For more information, see KB 5004622.

Issues that this cumulative update fixes

This cumulative update also fixes the issues that are described in the following Microsoft Knowledge Base articles:

  • 5012757 "Migration user... can't be found" error when using Start-MigrationUser after batch migration fails

  • 5012760 You can't access OWA or ECP after installing the July 2021 security update

  • 5012761 External attendees see “Send the Response Now” although no response was requested in Exchange Server

  • 5012765 Email stuck in queue starting from "2022/1/1 00:01:00 UTC+0" on all Exchange on-premises servers

  • 5012768 Start-MigrationUser and Stop-MigrationUser are unavailable for on-premises Exchange Server 2019 and 2016

  • 5012774 Can't change default path for Trace log data in Exchange Server 2019 and 2016

  • 5012779 Invalid new auth certificate for servers that are not on UTC time zone

  • 5012780 Disable-Mailbox does not remove LegacyExchangeDN attribute from on-premises Exchange 2019

  • 5012781 Exchange Server 2019 and 2016 DLP doesn’t detect Chinese resident ID card numbers

  • 5012782 MS ExchangeDiagnostic Service causes errors during service startup and initialization in Microsoft Exchange 2019

  • 5012783 Can't restore data of a mailbox when LegacyDN is empty in the database

  • 5012784 Exchange 2016 CU21 and Exchange 2019 CU10 cannot save "Custom Attributes" changes in EAC

  • 5012786 Forwarded meeting appointments are blocked or considered spam

  • 5012787 Download domains created per CVE-2021-1730 don’t support ADFS authentication in OWA

  • 5012789 Can't use Copy Search Results after eDiscovery & Hold search

  • 5012791 MailboxAuditLog doesn't work in localized (non-English) environments

  • 5012829 Group metrics generation fails in multidomain environment

Get Cumulative Update 23 for Exchange Server 2016

Download Center

Download Download Cumulative Update 23 for Exchange Server 2016 (KB5011155)

Download Download Exchange Server 2016 CU 23 UM Language Packs

Volume Licensing Center

To get Cumulative Update 23 for Exchange Server 2016, go to Microsoft Volume Licensing Center.


  • The Cumulative Update 23 package can be used to run a new installation of Exchange Server 2016 or to upgrade an existing Exchange Server 2016 installation to Cumulative Update 23.

  • You don't have to install any previously released Exchange Server 2016 cumulative updates or service packs before you install Cumulative Update 23.

File information

File hash information

File name

SHA256 hash





Change history

 The following table summarizes some of the most important changes to this topic.



August 30, 2021

Added a "New feature in this cumulative update" section.

September 28, 2021

Added "Notice" at the top of the article.

Need more help?

Want more options?

Explore subscription benefits, browse training courses, learn how to secure your device, and more.

Communities help you ask and answer questions, give feedback, and hear from experts with rich knowledge.

Was this information helpful?

What affected your experience?
By pressing submit, your feedback will be used to improve Microsoft products and services. Your IT admin will be able to collect this data. Privacy Statement.

Thank you for your feedback!