Bilateral chat policy is a new type of policy for restricting external group chats in Microsoft Teams to maximum of two organizations.
When enabled it will prohibit users from adding external users from more than 2 organizations to external group chats.
It applies to all Teams client – for Windows, MacOS, Android and iOS.
It does not apply to meetings, meeting chats or channels.
When trying to add or create an external chat with users from more than 2 organizations, users will be notified.
To enable this policy, you can use either Teams administration portal or PowerShell.
In the Teams administration portal, the option is available at the external access policies
With PowerShell you need to use the CsExternalAccessPolicy command and assign it
New-CsExternalAccessPolicy –Identity <policy name> -FederatedBilateralChats $True
Grant-CsExternalAccessPolicy -PolicyName EnableBilateral –Identity <email address>