Microsoft is rolling out new administrative controls for Microsoft Teams that let businesses decide which outside organisations staff can chat with in shared group chats.

• What it is: Two new PowerShell settings give admins the ability to restrict which external tenants can join federated group chats in Teams, rather than allowing this by default.
• Who is affected: Any business using Microsoft Teams for external collaboration. The settings are disabled by default and rolling out globally between late July and late September 2026.
• The risk: Without these controls, staff can be added to group chats by contacts at any external organisation, an avenue sometimes used for phishing and social engineering.
• What to do: Once the update reaches your tenant, review your Teams external access settings and decide whether to restrict federated group chats to approved organisations only.

We recommend reviewing these settings with your IT provider once they appear in your admin centre, particularly if your business handles sensitive client information over Teams.

Source: TechRadar