Teams Group Chats Can Now Include External (Federated) Participants

External Access Via Teams Connect

When Microsoft announced Microsoft Teams Connect in March, the focus was firmly on shared channels as a new way to collaborate with people external to an organization in a channel. Shared channels use the existing Teams federation capability to communicate with external members (who don’t need guest accounts). By default, Teams uses open federation, which means that you can communicate with any other Teams user in a Microsoft 365 tenant. Administrators can control the domains users can communicate with by adding domains to a list in the External access section of the Teams admin center and setting their status to be allowed or blocked (Figure 1).

External access settings in the Teams admin center
Figure 1: External access settings in the Teams admin center

Up to now, the external access list has only been used to control federated 1:1 chat (including calls) between users in other domains. In the future, collaboration using shared channels will use the same list, so it’s important to keep it updated.

Federated Group Chats

On May 11, message center notification MC255536 announced an enhancement to chat (roadmap item 51126) to allow external participation in group chats. In effect, extended federated chat moves from its previous 1:1 limitation to allow external users from other tenants (they must have an Azure AD account) to join group chats of up to 250 participants. Roll-out to tenants begins in mid-May with completion due in late July.

When the new software is available, you’ll be able to add external participants to group chats like any other tenant or guest account. To add an external person, enter their email address as a participant and then use the Search externally option (Figure 2). Teams checks the external access domain list to discover if federated chat is allowed with the participant’s domain, and if it is, looks up Azure AD to find their account. If the account exists, Teams adds it to the chat.

Searching for an external participant to join a group chat
Figure 2: Searching for an external participant to join a group chat

Of course, the domain for the external participant might block federated communications with your domain. If this is the case, the chat can’t happen.

As shown in Figure 3, once a group chat has an external participant, Teams displays a prominent External label to advise everyone that they shouldn’t discuss company confidential information (unless it’s appropriate to share the information with an external person). External participants are also marked as such in the participant roster.

Teams group chat with an external (federated) participant
Figure 3: Teams group chat with an external (federated) participant

Shared Channels Next

Microsoft hasn’t given a recent update about the progress of shared channels or an expected delivery date, but the feature is expected “later this year.” Adding federated capability to group chats is a logical step. Chats are often used to resolve issues before decisions are brought back for wider comment in channel conversations. It wouldn’t make much sense to be able to collaborate with groups of external users in a shared channel if you couldn’t chat with the same people.


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