It’s not really something new, but I have found that many (new) Microsoft Teams user do not know that
- invitations can be sent to all existing email addresses out there, even if they are not licensed to Office 365 or connected to Azure AD. This also includes public consumer accounts such as Gmail, Outlook.com, Yahoo etc.
- People who have received meeting invitation links can join meetings anonymously without having to authenticate themselves. Of course this also works with copy & paste or if the link is forwarded.
Especially in the current situation with the Coronavirus and many people who are working from home, these two functionalities are useful to set up online meetings easily and quickly.
To turn off that anonymous users can join a meeting go to https://admin.teams.microsoft.com with an administrator account, click on Meetings in the menu on the left and select Meeting settings.
Adjustments to the policies for participation of anonymous users in Team Meetings can be made under Meeting Policies. I recommend creating a custom policy for this.
Read this Microsofts Docs article about managing meeting policies in Teams:
https://docs.microsoft.com/en-us/microsoftteams/meeting-policies-in-teams
