MC1166867 - Microsoft Defender for Office 365: Enhancing the quarantine email preview experience

Updated February 18, 2026: We have updated the content. Thank you for your patience. 

We’re improving the email preview experience in Microsoft Defender for Office 365 to provide a clearer, more consistent, and secure workflow. These updates are designed to reduce ambiguity, simplify interactions, and reinforce security protections—helping organizations confidently use this feature as part of their protection strategy.

When this will happen:

General Availability (Worldwide): Rollout will begin in early Novembermid-October 2025 (previously mid-October) and is expected to complete by mid-December 2025 (previously early November).November 2025.

General Availability (GCC, GCCH, and DoD): Rollout will begin in mid-Novemberlate October 2025 (previously late October) and is expected to complete by mid-December 2025 (previously mid-November).November 2025.

How this affects your organization:

Who is affected: Quarantine usersadministrators Microsoft Defender for Office 365 as well as users with access to review and preview messages within quarantine.

The update is specifically for the preview capability within the quarantine experience. What will happen:

• The update consists of three main parts:
  • Streamlined view options: The plain text view option will be retired for users to unify preview behaviors across Defender experiences. It will still be present for admins.
  • Clearer handling of URLs: The hover-over preview for URLs will be limited for users to reinforce that links in quarantine preview are not clickable.
  • Simplified content loading: The “Load external content” button will be removed for some scenarios. Content will render in a secure, isolated environment.

Quarantine administrators and users will experience a simplified preview interface with clearer rendering and reduced visual cues for URL interactivity:

What you can do to prepare:

• Update any internal documentation that references the quarantine preview experience.
• Communicate these changes to helpdesk and support teams to reduce confusion.
• No configuration changes are required; the update will apply automatically.

Compliance considerations:

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