check before: 2026-01-01
Product:
Defender, Defender for Office 365, Defender XDR, Microsoft 365 admin center, Teams
Platform:
Online, Web, World tenant
Status:
Launched
Change type:
Admin impact, New feature, Updated message
Links:
Details:
Summary:
Starting mid-February 2026, admins can block external Microsoft Teams users via the Tenant Allow/Block List in the Microsoft Defender portal, controlling access and deleting existing communications. This applies to Teams and Defender XDR, with audit logging and limits of 4,000 domains and 200 emails blocked.
Details:
Updated January 23, 2026: We have updated the timeline. Thank you for your patience.
[Introduction]
We're introducing an integration between Microsoft Teams and Microsoft Defender for Office 365 that allows security admins to manage blocked external users in Teams through the Tenant Allow/Block List (TABL) in the Microsoft Defender portal. This centralized approach enhances security and compliance by enabling organizations to control external user access across Microsoft 365 services.
This message is associated with Roadmap ID 542189.
[When this will happen:]
General Availability (Worldwide): Rollout begins mid-February 2026 (previously early January) and is expected to complete by end of February 2026 (previously mid-January).
Change Category:
XXXXXXX ... free basic plan only
Scope:
XXXXXXX ... free basic plan only
Release Phase:
General Availability
Created:
2025-12-19
updated:
2026-01-24
Task Type
XXXXXXX ... free basic plan only
Docu to Check
XXXXXXX ... free basic plan only
MS How does it affect me
XXXXXXX ... free basic plan only
MS Preperations
XXXXXXX ... free basic plan only
MS Urgency
XXXXXXX ... free basic plan only
MS workload name
XXXXXXX ... free basic plan only
linked item details
XXXXXXX ... free basic plan only
Pictures
XXXXXXX ... free basic plan only
summary for non-techies**
Starting in mid-February 2026, administrators will be able to block external users from accessing Microsoft Teams using the Tenant Allow/Block List (TABL) managed through the Microsoft Defender portal, ensuring secure communications by preventing blocked users from sending messages, joining meetings, or making calls.
Direct effects for Operations**
Blocking External Users
If the change is implemented without preparation, users may suddenly lose access to important communications from external partners, leading to disruptions in collaboration and project delays.
- roles: Security Admins, End Users
- references: https://learn.microsoft.com/microsoft-365/security/office-365-security/tenant-allow-block-list, https://www.microsoft.com/microsoft-365/roadmap?filters=&searchterms=542189
Deletion of Existing Communications
Existing communications from blocked external users will be automatically deleted, which may result in loss of critical information and context for ongoing discussions.
- roles: Security Admins, End Users
- references: https://learn.microsoft.com/microsoft-365/security/office-365-security/tenant-allow-block-list, https://www.microsoft.com/microsoft-365/roadmap?filters=&searchterms=542189
Audit Logging and Compliance
Without proper preparation, the audit logs may not be adequately monitored, leading to compliance issues if actions taken are not documented or reviewed properly.
- roles: Security Admins, Compliance Officers
- references: https://learn.microsoft.com/microsoft-365/security/office-365-security/tenant-allow-block-list, https://www.microsoft.com/microsoft-365/roadmap?filters=&searchterms=542189
Configutation Options**
XXXXXXX ... paid membership only
Opportunities**
XXXXXXX ... free basic plan only
Potentional Risks**
XXXXXXX ... paid membership only
Data Protection**
XXXXXXX ... paid membership only
IT Security**
XXXXXXX ... paid membership only
Hypothetical Work Council Statement**
XXXXXXX ... paid membership only
DPIA Draft**
XXXXXXX ... paid membership only
explanation for non-techies**
XXXXXXX ... free basic plan only
** AI generated content. This information must be reviewed before use.
a free basic plan is required to see more details. Sign up here
A cloudsocut.one plan is required to see all the changed details. If you are already a customer, choose login.
If you are new to cloudscout.one please choose a plan.
change history
| Date | Property | old | new |
| 2026-01-24 | MC MessageTagNames | New feature, Admin impact | Updated message, New feature, Admin impact |
| 2026-01-24 | MC Summary | Admins can now block external users in Microsoft Teams via the Tenant Allow/Block List in the Microsoft Defender portal, controlling access and communications. This feature, rolling out January 2026, supports up to 4,000 domains and 200 emails, with audit logging and no impact on existing Teams settings. | Starting mid-February 2026, admins can block external Microsoft Teams users via the Tenant Allow/Block List in the Microsoft Defender portal, controlling access and deleting existing communications. This applies to Teams and Defender XDR, with audit logging and limits of 4,000 domains and 200 emails blocked. |
| 2026-01-24 | MC Last Updated | 12/19/2025 08:08:18 | 2026-01-24T01:51:04Z |
| 2026-01-24 | MC Messages | [Introduction]
We're introducing an integration between Microsoft Teams and Microsoft Defender for Office 365 that allows security admins to manage blocked external users in Teams through the Tenant Allow/Block List (TABL) in the Microsoft Defender portal. This centralized approach enhances security and compliance by enabling organizations to control external user access across Microsoft 365 services. This message is associated with Roadmap ID 542189. [When this will happen:] General Availability (Worldwide): Rollout begins early January 2026 and is expected to complete by mid-January 2026. | Updated January 23, 2026: We have updated the timeline. Thank you for your patience.
[Introduction] We're introducing an integration between Microsoft Teams and Microsoft Defender for Office 365 that allows security admins to manage blocked external users in Teams through the Tenant Allow/Block List (TABL) in the Microsoft Defender portal. This centralized approach enhances security and compliance by enabling organizations to control external user access across Microsoft 365 services. This message is associated with Roadmap ID 542189. [When this will happen:] General Availability (Worldwide): Rollout begins mid-February 2026 (previously early January) and is expected to complete by end of February 2026 (previously mid-January). |
| 2026-01-24 | MC Title | Microsoft Defender for Office 365: Admins can block external users in Microsoft Teams from Defender Portal | (Updated) Microsoft Defender for Office 365: Admins can block external users in Microsoft Teams from Defender Portal |
| 2026-01-24 | MC End Time | 02/13/2026 09:00:00 | 2026-03-30T10:00:00Z |
Last updated 3 weeks ago ago
