TL;DR:
Teams users will soon see an invitation pop-up to accept or block an external user when receiving new chats from external users. Due mid-August to early September.

Details:
When receiving a new one-on-one chat from an external user, Teams users will receive an invitation to accept or block that user. This also provides the ability to block external users at any point, which revokes access to presence and incoming messages.

Availability:
Due mid-August to early September.

Check status:
Microsoft 365 Roadmap ID 94646

Page originally published:
16th July  2022 and kept up to date.

MC400204