Block External Teams Users Directly from the Defender Portal

Managing external access in Microsoft Teams has often been challenging.

Starting January 2026, security teams will be able to block external users in Teams directly through the Tenant Allow/Block List (TABL) in the Microsoft Defender portal.

Why this is important:

• Centralized management through a single security portal

• Ability to instantly block external chats, calls, meetings, and channel messages

• All actions are recorded for audit and compliance purposes

• Existing Teams federation settings remain unaffected

Required actions:
Security administrators must enable two settings in Teams Admin Center > Users > External Access > Organization Settings:

• Block specific users from communicating with people in the organization

• Allow the security team to manage blocked domains and users

Availability: January 2026
For: Defender for Office 365 customers

This is a key update to review before rollout.

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