Microsoft Defender for Office 365: Admins can block external users in Microsoft Teams from Defender Portal

Microsoft's description

Security admins with Defender for Office 365 Plan 1 and above can block external users from sending messages, calls, meetings invitation over Microsoft Teams via the Tenant Allow Block List in Microsoft Defender portal. Updated January 28, 2026: We are pausing rollout at this time as we address an ongoing issue. We apologize for any inconvenience.