Microsoft Defender for Office 365 is enhancing quarantine for admins by listing messages by individual recipients, improving backend durability, and requiring message release per user. Rollout begins January 2026, completing by March. No changes affect end users. Admins should update practices and documentation accordingly.
Day in brief
Block domains and addresses in Microsoft Teams using the Tenant Allow/Block List leads 9 Defender updates
9 January 2026 recorded 1 new, 6 updated, 1 removed Microsoft Defender documentation changes and 1 relevant Message Center announcement. The most active areas were Office 365, Endpoint, Defender XDR.
- Block domains and addresses in Microsoft Teams using the Tenant Allow/Block List
Office 365 · Email and collaborationAdded Microsoft Defender documentation in defender-office-365/tenant-allow-block-list-teams-domains-configure.md.
- Microsoft Defender Core service overview
Endpoint · Endpoint protectionUpdated Microsoft Defender documentation in defender-endpoint/microsoft-defender-core-service-overview.md.
- Troubleshoot Microsoft Defender Antivirus service startup problems
Endpoint · TroubleshootingUpdated Microsoft Defender documentation in defender-endpoint/troubleshoot-service-startup-problems.md.
- Microsoft Defender for Endpoint - Mobile Threat DefenseEndpoint · Endpoint protection
Updated Microsoft Defender documentation in defender-endpoint/mtd.md.
- Microsoft Defender for Office 365: Enhancing the quarantine experience for administrators
Defender XDR · Email and collaborationMicrosoft Defender for Office 365 is enhancing quarantine for admins by listing messages by individual recipients, improving backend durability, and requiring message release per user. Rollout begins January 2026, completing by March. No changes affect end users. Admins should update practices and documentation accordingly.
This period briefing was assembled from the tracked Microsoft Learn and Message Center changes.
9 updates
Microsoft Defender XDR
1 updateMicrosoft Defender for Endpoint
4 updatesUpdated Microsoft Defender documentation in defender-endpoint/microsoft-defender-core-service-overview.md.
Updated Microsoft Defender documentation in defender-endpoint/mtd.md.
Updated Microsoft Defender documentation in defender-endpoint/troubleshoot-service-startup-problems.md.
Linux Whatsnew
UpdatedUpdated Microsoft Defender documentation in defender-endpoint/linux-whatsnew.md.
Microsoft Defender for Office 365
4 updatesAdded Microsoft Defender documentation in defender-office-365/tenant-allow-block-list-teams-domains-configure.md.
Mdo Support Teams About
UpdatedUpdated Microsoft Defender documentation in defender-office-365/mdo-support-teams-about.md.
Updated Microsoft Defender documentation in defender-office-365/tenant-allow-block-list-about.md.
Removed Microsoft Defender documentation in defender-office-365/tenant-allow-block-list-teams-configure.md.