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Exchange Server Subscription Edition RTM Exchange Server Subscription Edition RTM Hotfix update

KB5066373

KB5066373: Hotfix update for Exchange Server Subscription Edition RTM, September 2025. Fixes failed online archiving for hybrid on-premises mailboxes

In short

Online archiving works again for affected hybrid Exchange mailboxes after this hotfix, which addresses a non-security issue.

Does it affect you? Applies to: Exchange Server Subscription Edition RTM deployments. The issue affects hybrid environments where the archive mailbox is in Exchange Online and the primary mailbox is on-premises.

Build
15.2.2562.27
Servicing branch
RTM
Restart
Required

What changes

Fix 1 change

Online archiving

For: Hybrid Exchange administrators

  • Retention-tagged items configured to move to an online archive are moved automatically again for affected hybrid mailboxes.1
    The fix applies when the dedicated Exchange Hybrid Application is enabled, the archive is in Exchange Online, and 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
RTM
Restart
Required
Replaces
KB5063224
Replaced by
KB5066366
VersionBuildChannel
SE 15.2.2562.27 General availability

Security

No vulnerabilities are listed for this update.

Sources

Updated
Cited passages from Microsoft's official notes (1)
  1. 1. - 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 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