Microsoft Defender for Office 365: Enhancing the quarantine experience for administrators

Originally posted by Microsoft Oct 14, 2025 Uncategorized 0 Comments

Microsoft Defender for Office 365 is enhancing quarantine for admins by listing messages by individual recipients, improving backend durability, and maintaining existing cmdlets with adjusted functionality. Rollout starts November 2025. No changes affect end users. Admins should update practices and documentation accordingly.

We’re improving the quarantine experience in Microsoft Defender for Office 365 to deliver greater clarity, visibility, and ease of use for administrators. These updates include backend enhancements for improved durability and consistency as well as experience updates to list messages in quarantine by individual recipients to simplify navigation and management.

When this will happen:

• General Availability (Worldwide and GCC): We will begin rolling out in early November 2025 and expect to complete by mid-December 2025.
• General Availability (GCCH and DoD): We will begin rolling out in early December 2025 and expect to complete by early January 2026.

How this affects your organization:

• Who is affected: Administrators managing quarantined messages in Microsoft Defender for Office 365.
• What will happen:
  • Quarantined messages will now be listed by individual recipient instead of grouped by multiple recipients.
  • Backend enhancements will improve durability and consistency.
  • Existing quarantine release cmdlets will all remain functional. Administrators should be cognizant that `ReleaseToAll` now applies to a single user as aggregation has been removed. Admins must release messages for each intended mailbox individually.
  • No changes to end-user experience.

Screenshot 1 – Updated quarantine view showing individual recipients listed separately in the Recipient column:

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Screenshot 2 – Existing quarantine view showing multiple recipients in the Recipient column:

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What you can do to prepare:

• Review your organization’s quarantine release practices.
• Update any internal documentation to reflect the new recipient-level view.
• Communicate this change to helpdesk or support teams as needed.
• Learn more: 
  • Microsoft Defender for Office 365 overview | Microsoft Learn
  • Manage quarantined messages and files as an admin | Microsoft Defender for Office 365 | Microsoft Learn

Compliance considerations:

No compliance considerations identified, review as appropriate for your organization.

Message ID: MC1171845