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

KB5066372

KB5066372: Hotfix update for Exchange Server 2019 CU15, September 2025. Hybrid online archiving resumes automatic moves to archive

In short

Automatic moves to Exchange Online archives work again for on-premises mailboxes in a hybrid setup using the dedicated Exchange Hybrid Application feature.

Does it affect you? Applies to: Exchange Server 2019 CU15 deployments enrolled in the Extended Security Update (ESU) program.

Build
15.2.1748.37
Servicing branch
CU15

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

Fix 1 change

Online archiving

  • Items tagged to move to an online archive are automatically moved again for on-premises users in a hybrid setup.1
    Resolves the issue that occurs after enabling the dedicated Exchange Hybrid Application feature when the archive mailbox is in Exchange Online and the primary mailbox remains on an on-premises Exchange Server.

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
CU15
Replaces
KB5063221, KB5057651
Replaced by
KB5066367
VersionBuildChannel
2019 15.2.1748.37 General availability

Security

No vulnerabilities are listed for this update.

Sources

Updated
Cited passages from Microsoft's official notes (1)
  1. 1. Hotfix update for Exchange Server 2019 CU15 HU4: September 8, 2025 (KB5066372) 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 4/5, clarity 5/5, 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