Short version:
This new external group chat feature enables you to initiate and participate in group Teams chats with users from outside your organisation, external group chat in Teams supports up to 250 participants across multiple organisations in a single chat. Due mid-May to late July.
Details:
This new external group chat feature enables you to initiate and participate in group Teams chats with users from outside your organisation. Expanding on the existing ability for Teams users to find, participate in 1:1 chat, call and set up meetings with external users, external group chat in Teams supports up to 250 participants across multiple organisations in a single chat.
Once your organisation is federated with another organisation/or use the open federation policy, you can initiate a chat in the same way you would with someone inside your organisation. Simply tap on the new Chat icon, enter the email address of the recipient, and tap the Search externally option to find the user. You can add up to 250 participants to a single group chat.
Admin stuff:
Open federation is the default setting in Teams. If you wish to limit the organisations your users can contact or can be contacted by, and the groups and users that can participate, you can manage the allowed or blocked domains and users lists from the Teams Admin Center.
External group chat is part of Microsoft Teams Connect. Azure Active Directory (AAD) is required. The organisations are required to use the open federation policy or be on each other’s allow list.
This rollout of external group chats will not change any previous organisational settings. All legacy settings will be honored.
Availability:
Microsoft will begin rolling this out in mid-May and expect to complete rollout late July on Teams desktop, web and mobile.
Links:
Related blog. Additional information
