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Exchange Server 2019 CU14 Exchange Server 2019 CU14 ESU only Hotfix update

KB5066371

KB5066371: Hotfix update for Exchange Server 2019 CU14, September 2025. Automatic online archiving works again in hybrid environments

In short

This hotfix restores automatic movement of archive-tagged items to Exchange Online archives when the primary mailbox is on-premises in a hybrid environment.

Does it affect you? Applies to: Exchange Server 2019 CU14 devices at organizations enrolled in the Extended Security Update program. This hotfix is available only to those organizations.

Build
15.2.1544.34
Servicing branch
CU14

For servers running Cumulative Update 14: 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

Fix 1 change

Online archiving

For: Exchange administrators in hybrid environments

  • Items tagged to move to an online archive are automatically moved again when the primary mailbox is on-premises in a hybrid environment.1
    Fixes the issue that occurs after enabling the dedicated Exchange Hybrid Application, when a retention tag configured as Move to Archive does not move items to an Exchange Online archive mailbox while the primary mailbox remains on-premises.

Technical details

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

Data sheet

Released
2025-09-08
Classification
Updates
Type
Cumulative update
Servicing branch
CU14
Replaces
KB5063222, KB5057652
Replaced by
KB5066368
VersionBuildChannel
2019 15.2.1544.34 General availability

Security

No vulnerabilities are listed for this update.

Sources

Updated
Cited passages from Microsoft's official notes (1)
  1. 1. ## Issues that this hotfix update fixes - [Online archiving fails for on-premises users in hybrid environment] support.microsoft.com
Checked automatically: 8 of 8 checks passed, 1 quoted passage · 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 5/5, clarity 4/5, completeness 5/5. 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