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Microsoft Teams to integrate external user blocking via Defender for Office 365

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Microsoft will introduce a new feature in Microsoft Teams that allows security administrators to block external users from sending messages, calls, or meeting invitations to their organization's members. This feature will be integrated with Defender for Office 365, enabling centralized management of blocked external contacts through the Tenant Allow/Block List in the Microsoft Defender portal. The rollout begins in early January 2026 and is expected to complete by mid-January 2026. The feature aims to enhance security and compliance by preventing cybercrime gangs, including ransomware groups, from exploiting Teams for social engineering attacks. Additionally, Teams will warn admins about suspicious traffic from external domains and automatically strengthen messaging security by default.

Timeline

  1. 24.12.2025 18:22 1 articles · 23h ago

    Microsoft Teams to integrate external user blocking via Defender for Office 365

    Microsoft will introduce a new feature in Microsoft Teams that allows security administrators to block external users from sending messages, calls, or meeting invitations to their organization's members. This feature will be integrated with Defender for Office 365, enabling centralized management of blocked external contacts through the Tenant Allow/Block List in the Microsoft Defender portal. The rollout begins in early January 2026 and is expected to complete by mid-January 2026. The feature aims to enhance security and compliance by preventing cybercrime gangs, including ransomware groups, from exploiting Teams for social engineering attacks. Additionally, Teams will warn admins about suspicious traffic from external domains and automatically strengthen messaging security by default.

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