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Microsoft released Cumulative Update 13 for Exchange Server 2019 (KB5020999) on May 3, 2023. Also known as Exchange Server 2019 CU13. 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 2019.


How to update Exchange Server 2019 to CU13?

It’s recommended to update the Exchange Server in the lab environment before updating it in the production environment.

  1. Download Cumulative Update CU13 for Exchange Server 2019 (KB5020999)
  2. Update to Microsoft .NET Framework 4.8
  3. Install Exchange Cumulative Update

Cumulative Update CU13 for Exchange Server 2019 is released as version 15.02.1258.012. Which version are you running now? Read more on how to find your Exchange version build number.

Cumulative Update 13 for Exchange Server 2019 download

New features in Cumulative Update 13

  • 5027150 Enable Modern Auth for pure On-Premises Exchange users
  • To make it easier to install CUs, some improvements were made to the installation experience. A common issue for many customers is that CUs overwrite various configuration files (for example, web.config and sharedweb.config) that contain custom settings such as client-specific message size limits.

    Historically, these customizations are lost after a CU is installed, and an admin must reapply them. Because of this, admins often backup and restore their custom settings or use scripts to recreate custom settings after installing a CU.

    To address this, Setup now backs up the most common configuration settings and then restores them to the state they were in before Setup was started. Starting with the 2023 H1 CU, Setup preserves about 70 different configuration settings across multiple files.

    For more information about this feature, see Exchange Server custom configuration preservation.

Issues fixed in Cumulative Update 13

This Cumulative Update fixes the issues that are described in the following Microsoft Knowledge Base articles:

  • 5026134 “InvalidRecipientsException” when you try to run MRM
  • 5026135 CertificateDeploymentServicelet failure in multiple domain forest Exchange deployments
  • 5026136 Microsoft Exchange Transport doesn’t re-encrypt IRM messages
  • 5026138 Users receive reminders although the meeting reminder is set to None
  • 5026139 You can’t move the public folder mailbox
  • 5026142 Journal message returns “ConversionFailedException”
  • 5026143 OAB shadow distribution threshold must be reduced or made configurable
  • 5026146 Expiry notification is sent to moderator and sender for approved and delivered messages
  • 5026147 BlockLegacyAuthentication fail Organization Policy because of BackendRehydrationModule implementation
  • 5026149 Group metrics generation doesn’t finish in multidomain environment
  • 5026150 Edge server Filtering Agent removes journal attachments
  • 5026151 Oab-Processing-Threshold is set to 0 for On-Premises
  • 5026152 Microsoft Exchange ActiveSync or Current Requests counter inaccurately counts requests
  • 5026153 Delivery Flow Control setting override is now available
  • 5026154 On-premises Exchange has 35MB file size limit for online archiving
  • 5026155 “No support for this operation” error on an Exchange 2019 DAG member server
  • 5026156 Outlook search fails in a shared On-Premises mailbox if the primary user mailbox is migrated to Exchange Online
  • 5026158 The body of recurring meeting is not clear if it has Chinese characters
  • 5026159 IconIndex returns Default value when Server Assisted Search is used in Outlook
  • 5026266 “Could not start MS Exchange Service Host service” error and Exchange stops responding
  • 5026267 OWA stops responding in an Exchange 2019 and 2016 coexistence topology
  • 5026268 Store Worker process crashes and returns “System.NullReferenceExceptions” multiple times per day
  • 5026269 Block deserialization error when using eDiscovery
  • 5026271 IIS URL Rewrite Module link is incorrect
  • 5026273 Outlook configuration fails in Android or iOS
  • 5026274 Hybrid Agent Validation fails after Extended Protection is enabled
  • 5026277 Mail configuration fails on iOS device after Extended Protection is enabled
  • 5026278 Mailbox migration fails after Extended Protection is enabled

Known issues in Cumulative Update 13

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.

File hash information

  • File name: ExchangeServer2019-x64-cu13.iso
  • SHA256 hash: F6CCD5B3541DE044BA7BD5F756C02AE3C791C7B4DD1CA7136BEE8262B0390806

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