How a guest joins a team
A team owner in Microsoft Teams can add and manage guests in their teams via the web or desktop. Anyone with a business or consumer email account, such as Outlook, Gmail, or others, can participate as a guest in Teams with full access to team chats, meetings, and files. Only people who are outside of your organization, such as partners or consultants, can be added as guests. People from within your organization can join as regular team members.
Before guests can join a team, an admin must enable guest access in Teams. To do that, see Turn on or off guest access for Microsoft Teams.
Here's how a guest becomes a member of a team:
Step 1 A team owner or an Office 365 admin adds a guest to a team.
Step 2 The Office 365 admin or the team owner can manage a guest's capabilities as necessary. For example, allowing a guest to add or delete channels or disabling access to files.
Step 3 The guest receives a welcome email from the team owner, with information about the team and what to expect now that they're a member. Guest users who have an email address that belongs to an Azure Active Directory or Office 365 work or school account can accept the invitation directly. If the guest doesn’t yet have a Microsoft Account associated with their email address, they will be directed to create one for free. After accepting the invitation, the guest can participate in teams and channels, receive and respond to channel messages, access files in channels, participate in chats, join meetings, collaborate on documents, and more.
While using Teams, text and icons give all team members clear indication of guest participation in a team. A guest user's name includes the label (Guest), and a channel includes an icon to indicate that there are guests on the team. For more details, see What the guest experience is like.
Guests can leave the team at any time via Teams web and desktop clients. For details, see How do I leave a team?
Leaving the team doesn't remove the guest account from the organization/tenant. See Leave an organization as a guest user on how to remove yourself from the organization. Alternatively, the organization's admin can remove guest users from the tenant.