MS Teams allows users without MS accounts to find, call, chat, and set up meetings with people in the organization who use Teams. However, they have to register MS Teams account firstly.
It requires that external users must register MS Teams accounts before joining, chatting or setting any meetings in MS Teams.
Go to the link to register MS Teams account. Enter your email address, then click Next
Microsoft Teams will ask you to use Windows App or Web App, Click on Use the web app instead
On the screen, choose For work and organizations
Sign in again with the email account which you entered earlier.
Enter the verification code sent to the mail by Microsoft
Enter your mobile phone number
Enter the verification code sent to your mobile phone by Microsoft
Microsoft will notify that you had already used this mobile number for another email account. Select Continue if you want to keep. Or Transfer number to change to another number for this account. In this scenario. click Continue
After all. You can now access Microsoft Teams. You must modify your name firstly
Now you can start a chat or join meetings in the organization.
Add External Users To Group Chat
External users must have MS Teams account before being added. How to register
In your group chat. Click Add people
Enter emails you'd like to add. Then Choose "Search email address externally"
After that, You can see the display name (External) as my picture below. Just add for finish.
