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Exchange Server 2019 CU15 Exchange Server 2019 CU15 ESU only Hotfix update

KB5057651

KB5057651: Hotfix update for Exchange Server 2019 CU15, May 2025. Edge Transport stalls and StoreWorker failures fixed

In short

This optional hotfix fixes four Exchange Server 2019 issues, including Edge Transport service failures and StoreWorker problems that can quarantine mailboxes. It also includes the November 2024 security updates.

Does it affect you? Applies to: Exchange Server 2019 CU15 x64 installations at organizations enrolled in the Extended Security Update program. The update produces build 15.2.1748.26.

Build
15.2.1748.26
Servicing branch
CU15
Review notes Additional details from the official release notes (3) Read notes
  • In detail This hotfix introduces new features as well as fixing nonsecurity issues.
  • Why do I have it? This is an ESU-only Exchange Server 2019 update. The KB describes it as an optional CU15 hotfix.
  • What to do The update is optional in Windows Update, and a standalone package is available from the Microsoft Download Center.

The official sources are linked at the end of the page.

For servers running Cumulative Update 15: each cumulative update gets its own update. Support for this version ended on October 14, 2025: Microsoft releases this update only to organizations enrolled in the Extended Security Update (ESU) program, not through Microsoft Update. The others should move to Exchange Server Subscription Edition. Which version am I on?

What changes

Fixes 4 changes

Journal messages

  • Fixes the journal message issue that returns “ConversionFailedException.”1

Calendar printing in OWA

  • Fixes the issue that prevents calendar printing in Outlook on the web.2

Edge Transport service

  • Fixes the issue that makes the Edge Transport service stop responding after certain updates.3

StoreWorker

  • Fixes the StoreWorker failure associated with BaseViewOperatorDefinition.4

Technical details

Data sheet · Security · Downloads · Components Click to collapse or expand

Data sheet

Released
2025-05-29
Classification
Updates
Type
Cumulative update
Servicing branch
CU15
Replaces
KB5050672
Replaced by
KB5063221
VersionBuildChannel
2019 15.2.1748.26 General availability

Security

No vulnerabilities are listed for this update.

Sources

Updated
Cited passages from Microsoft's official notes (4)
  1. 1. Journal message returns "ConversionFailedException" support.microsoft.com
  2. 2. Calendar print doesn't work in OWA from Exchange 2019 CU14 onwards support.microsoft.com
  3. 3. Edge Transport service stops responding after installing November 2024 SU or Exchange 2019 CU15 support.microsoft.com
  4. 4. StoreWorker fails because of BaseViewOperatorDefinition support.microsoft.com
Checked automatically: 8 of 8 checks passed, 4 quoted passages · compared with Microsoft's page on Oct 20, 2026
  • Quotes found in the official pages: passed
  • Numbers found in the sources: passed
  • Vulnerabilities from the dossier only: passed
  • Links to allowed domains only: passed
  • Every official change covered: passed
  • Readable plain text: passed
  • Changes confirmed by the file list: passed
  • Sources agree: passed

A second AI read the text against the sources: correctness 3/5, clarity 3/5, completeness 3/5. How we work

Published by The Update Bureau. Written with AI from Microsoft's own documents, checked by rules and a second AI. How we work · Report a mistake