Microsoft Teams – Now, users can chat with any teams users outside their organization.

Chatting with external users without needing to switch tenants enables you to get the results that you need faster. Let’s take a closer look at how it works.

Depending on the administrative settings of your organization and of the Teams personal account user:

• Start conversations with external Teams personal account users.
• External Teams personal account users can start conversations with Teams at work users.

Click on the below link for more information.

https://techcommunity.microsoft.com/t5/microsoft-teams-blog/microsoft-teams-users-can-now-chat-with-any-teams-user-outside/ba-p/3070832