Microsoft Teams Integration with Microsoft Defender for Office Tenant Allow/Block List for blocking domains
From Microsoft 365 Message Center Archive by Merill Fernando · Microsoft may not have sent this notice to your tenant.Rollout
- Roadmap
- 492985
Rollout dates are often only in the text. When Microsoft moves them, the change shows under "What changed".
Schedule dates changed in the text
Date phrases in schedule sentences differ between the versions this installation saw- Seen 16 Dec 2025
early January 2026, end of January 2026 - Seen 17 Nov 2025
late September 2025, early October 2025→ early January 2026, end of January 2026 - Seen 22 Aug 2025
mid-August 2025, mid-September 2025→ late August 2025, early September 2025, early October 2025
Read from date phrases in Microsoft's text, not from notice metadata. A changed phrase can be a moved rollout, a new milestone or just rewording; "What changed" below shows which.
What the notice says
Microsoft’s text, safely structuredUpdated December 16, 2025: We have updated the timeline. Thank you for your patience.
Introduction
We're introducing a new integration between Microsoft Teams and Microsoft Defender for Office 365 that enables security admins to manage blocked external domains in Teams using the Tenant Allow/Block List (TABL) in the Microsoft Defender portal. This feature enhances security by allowing organizations to centrally manage domain blocks across Microsoft 365 services.
This capability is available to customers with Microsoft Defender for Office 365 Plan 1 or Plan 2 and Microsoft Teams.
This message is associated with Microsoft 365 Roadmap ID 492985.
When this will happen
Targeted Release: We will begin rolling out late August 2025 and expect to complete by early September 2025.
General Availability (Worldwide): This is now generally available.
How this affects your organization
Security admins, with permission from Teams admins, will be able to:
- Add, delete, and view blocked external domains in Microsoft Teams using the Microsoft Defender portal.
- Prevent incoming communications (chats, channels, meetings, and calls) from blocked domains.
- Automatically delete existing communications from users in blocked domains.
- Track actions taken to block domains in audit logs, supporting compliance monitoring and reporting.
View and manage blocked domains for Teams in the Microsoft Defender portal:
This change does not affect existing federation configurations or domain blocks set in the Teams admin center.
- Entry limit: Up to 4,000 blocked domains can be configured for Teams.
- Client impact: Applies to all Teams clients and the Defender XDR web portal.
What you can do to prepare
To enable this feature -
- Ensure that external access in the Teams admin center is set to either:
- Block only specific external domains, or
- Allow all external domains
- Teams admins must enable the setting “Allow my security team to manage blocked domains” in the Teams admin center. This setting is off by default.
Enable security team access to manage blocked domains in the Teams admin center:
Learn more: Block domains in Microsoft Teams using the Tenant Allow/Block List | Microsoft Defender for Office 365 | Microsoft Defender | Microsoft Learn
Compliance considerations
| Does the change modify how admins can monitor, report on, or demonstrate compliance activities such as Purview or admin reporting? | Both Microsoft Teams and the Defender portal generate audit logs for actions taken on blocked domains. These logs can be accessed via Microsoft Purview or Defender audit capabilities. |
|---|---|
| Does the change provide a new way of communicating between users, tenants, or subscriptions? | Security admins can now block external domains in Microsoft Teams using the Tenant Allow/Block List, which affects cross-tenant communications across chats, channels, meetings, and calls. |
| Does the change include an admin control, and can it be controlled through Entra ID group membership? | Teams admins must enable the toggle “Allow my security team to manage blocked domains” in the Teams admin center to grant access. This control can be managed through Entra ID group membership. |
What changed
Between archive captures, newest firstUpdated
November 17,December 16, 2025: We have updated the timeline. Thank you for your patience. Introduction … 2025 and expect to complete by early September 2025. General Availability (Worldwide):We will begin rolling out early January 2026 (previously late September 2025) and expect to complete by end of January 2026 (previously early October 2025).This is now generally available. How this affects your organization Security admins, with permission from Teams admins, …Updated
August 22,November 17, 2025: We have updated the timeline. Thank you for your patience. Introduction … by early September 2025. General Availability (Worldwide): We will begin rolling out early January 2026 (previously late September20252025) and expect to complete by end of January 2026 (previously early October2025.2025). How this affects your organization Security admins, with permission from Teams admins, …- Tags
New feature, User impact, Admin impact→ Updated message, New feature, User impact, Admin impact
Updated August 22, 2025: We have updated the timeline. Thank you for your patience. Introduction We're introducing a new integration between Microsoft Teams and Microsoft Defender … 492985. When this will happen Targeted Release: We will begin rolling out
in mid-Augustlate August 2025 and expect to complete bymid-Septemberearly September 2025. General Availability (Worldwide): We will begin rolling outmid-Septemberlate September 2025 and expect to complete bylate Septemberearly October 2025. How this affects your organization Security admins, with permission from Teams …- Tags
- · first version seen
Learn more
Links from the notice and their documentation checksRelated public evidence
No related evidence found in this installation's recent collection. This does not establish that no announcement exists.
Not confirmed here
What this page cannot tell you- Whether your tenant is affected: this is Microsoft's notice, not a check of your settings.
- 1 linked page has not been read yet.