Microsoft Teams External Domains Anomalies Report MC1219794.3

Message ID: MC1219794 (Updated)

Updated February 27, 2026: We have updated the timeline. Thank you for your patience.

[Introduction]

To help admins detect unusual or potentially risky interactions with external organizations, Microsoft Teams is introducing the External domains anomalies report. This report analyzes cross-tenant communication patterns for your tenant and highlights sudden spikes or abnormal engagement activity. These insights support proactive investigation and help protect your organization while enabling secure external collaboration.

This message is associated with Microsoft 365 Roadmap ID 536572.

[When this will happen]

General Availability (Worldwide): Rolling out in early April 2026 (previously early March) and expected to complete in mid-April 2026 (previously mid-March).

[How this affects your organization]

Who is affected:

Teams administrators can view this report for their Microsoft 365 tenant if their organization collaborates with external organizations.

What will happen:

A new External domains anomalies report will be available in the Microsoft Teams admin center under Protection reports.
Admins can select Communication anomalies, choose a date range, and run the report to view results:
Insights include external domains with unusual communication activity:
- External domain name
- Total anomalies detected
- New 1:1 threads created by that domain
- New group threads created by that domain
A Block option is available directly in the report for managing external domains:

[What you can do to prepare]

No action is required to access the report.

To receive proactive alerts:

Enable External domains anomalies alerts in the Teams admin center:
- Go to Notifications & alerts > Rules.
- Select External domains anomalies.
- Set status to Active.
Specify a Teams channel for notifications if desired.