First thing to know, you must be a team owner to add a guest in Teams
Sometimes you'll want to collaborate with people who aren't in your team’s organization. A lot of times you'll be doing that in email, but if you want to collaborate with them in Teams, you can add them as a guest. Guests have fewer capabilities than team members or team owners, but there's still a lot they can do. For a deeper look, see Guest capabilities in Teams.
Add a guest to your team
Guests must have a Microsoft 365 work or school account. If the guest doesn’t yet have a Microsoft account associated with their email address, they will be directed to create one for free.
To add a guest to your team in Teams:
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Select Teams
and go to the team in your team list.
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Select More options
> Add member.
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3. Enter the guest's email address. Anyone with a business or consumer email account, such as Outlook, Gmail, or others, can join your team as a guest.
4. Add your guest's name. Select Edit guest information
and type a friendly name for them. Be sure to take the time to do this now—you’ll need the help of an IT admin to do it later.
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5. Click Add. Guests will receive a welcome email invitation that includes some information about joining Teams and what the guest experience is like.
Follow the link to see What a Guest User Will See When Joining an MS Team.