Cumulative Update 19 for Exchange Server 2016

Applies to: Exchange Server 2016

Cumulative Update 19 for Microsoft Exchange Server 2016 was released on December 15, 2020. This cumulative update 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 resolves vulnerabilities, see Microsoft Common Vulnerabilities and Exposures CVE-2020-17117CVE-2020-17132CVE-2020-17141CVE-2020-17142CVE-2020-17143.

This update also includes new daylight saving time (DST) updates for Exchange Server 2016. For more information about DST, see Daylight Saving Time Help and Support Center.

Known issues in this cumulative update

  • In multidomain Active Directory forests in which Exchange is installed or has been prepared previously by using the /PrepareDomain option in Setup, this action must be completed after the /PrepareAD command for this cumulative update has been completed and the changes are replicated to all domains. Setup will try to run the /PrepareAD command during the first server installation. Installation will finish only if the user who initiated Setup has the appropriate permissions.
    • About the /PrepareDomain operation in multidomain:

      The /PrepareDomain operation automatically runs in the Active Directory domain in which the /PrepareAD command is run. However, it may be unable to update other domains in the forest. Therefore, a domain administrator should run the /PrepareDomain in other domains in the forest.
    • About the permission question:

      Because the /PrepareAD is triggered in Setup, if the user who initiates Setup isn't a member of Schema Admins and Enterprise Admins, the readiness check will fail, and you receive the following error messages.

      Error 1:

      Error 2:

      To avoid the errors, either the user should join Schema Admins and Enterprise Admins groups or another user in Schema Admins and Enterprise Admins groups should manually run the /PrepareAD for this Cumulative Update first. Then, the Exchange admin user can start Setup.

  • Autodiscover Event ID 1 occurs after you install Cumulative Update 14 for Exchange Server 2016. For more information, see KB 4532190.
  • PDF preview function in OWA leads to download action unexpectedly. For more information, see KB 4583558.

Issues that this cumulative update fixes

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

  • 4588297 Attachments can't be downloaded or previewed from Outlook Web App
  • 4583531 Design change about inline images will be forced to download but not open in a new tab of OWA in Exchange Server 2019 and 2016
  • 4583532 ELC MRM archiving fails due to DomainName in AuthServer in Exchange Server 2019 and 2016
  • 4583533 Exchange Server 2019 or 2016 installation fails with error "The user has insufficient access rights" 
  • 4583534 Event ID 65535 System.Runtime.Serialization errors in Application log in Exchange Server 2019 or 2016
  • 4583535 New-Moverequest, Resume-Moverequest, and Remove-Moverequest not logged in Audit logs in Exchange Server 2019 and 2016
  • 4583536 Set-MailboxFolderPermission is included in Mail Recipient Creation in Exchange Server 2019 and 2016
  • 4583537 Update Korean word breaker in Exchange Server 2019 and 2016
  • 4583538 Microsoft Teams REST calls exceed the default value of maxQueryStringLength in Exchange Server 2019 and 2016
  • 4583539 Non-breaking space is visible in message body in Outlook in Exchange Server 2019 and 2016
  • 4583545 Make DomainName in Authserver a multivalued parameter in Exchange Server 2019 and 2016

Get Cumulative Update 19 for Exchange Server 2016

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Download Download Cumulative Update 19 for Exchange Server 2016 (KB4588884) now

Download Download Exchange Server 2016 CU19 UM Language Packs now


  • The Cumulative Update 19 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 19.
  • You don't have to install any previously released Exchange Server 2016 cumulative updates or service packs before you install Cumulative Update 19.

Cumulative update information


This cumulative update requires Microsoft .NET Framework 4.8.

A component that's used within Exchange Server requires a new Visual C++ component to be installed together with Exchange Server. This prerequisite can be downloaded at Visual C++ Redistributable Packages for Visual Studio 2013. For more information, see KB 4295081.

For more information about the prerequisites to set up Exchange Server 2016, see Exchange Server 2016 prerequisites.

Restart requirement

You may have to restart the computer after you apply this cumulative update package.

Registry information

You don't have to make any changes to the registry after you apply this cumulative update package.

Removal information

After you install this cumulative update package, you can't uninstall the package to revert to an earlier version of Exchange Server 2016. If you uninstall this cumulative update package, Exchange Server 2016 is removed from the server.

File information

File hash information

File name SHA1 hash SHA256 hash


5840DCA054BC917C7E6534CAB3CDEE3A49D43358 548FCCAC2B1303960DF91F607DC79BBCD00D01374BCA1F9A7FAF58DB5147930C

More information

For more information about the deployment of Exchange Server 2016, see Release notes for Exchange Server 2016.

For more information about the coexistence of Exchange Server 2016 and earlier versions of Exchange Server in the same environment, see Exchange Server 2016 system requirements.

For more information about other Exchange updates, see Exchange Server Updates: Build numbers and release dates.


Learn about the terminology that Microsoft uses to describe software updates.