Guest is a user/license type in Microsoft Teams that is included with all Office 365 Business Premium, Office 365 Enterprise, and Office 365 Education subscriptions. No additional Office 365 license is necessary. Teams guest access is a tenant-level setting and is turned off by default. For details about how to enable guest access, see Turn on or off guest access to Microsoft Teams.
After the Guest user/license type is turned on, you can configure settings for guests via the controls described in Manage Microsoft Teams settings for your organization and Manage Teams during the transition to the new Microsoft Teams admin center.
IT admins can add guests at the tenant level, set and manage guest user policies and permissions, and pull reports on guest user activity. These controls are available through the Microsoft Teams admin center. Guest user content and activities are under the same compliance and auditing protection as the rest of Office 365.
Team owners can invite new guests and add existing directory guest users to their teams. Team owners can identify guest users via Teams > Manage teams, and set channel-related capabilities for guests via Org-wide settings > Guest access, including allowing guests to create, update, and delete channels, as shown in the following illustration.
You can use the Azure Active Directory (Azure AD) portal to manage guests and their access to Office 365 and Teams resources. Teams guest access makes use of Azure AD business-to-business (B2B) collaboration capabilities as the underlying infrastructure to store security principles information such as identity properties, memberships, and multi-factor authentication settings. To learn more about Azure AD B2B, see What is Azure AD B2B collaboration? and Azure Active Directory B2B collaboration FAQs.
Microsoft Teams always honors Azure AD external settings to allow or prevent guest user additions to the tenant. For more details, see Authorize guest access in Microsoft Teams.
Guest access vs. external access (federation)
External access (federation) and guest access are different:
Guest access gives access permission to an individual. External access gives access permission to an entire domain.
Guest access, once granted by a team owner, allows a guest to access resources, such as channel discussions and files, for a specific team, and chat with other users in the team they have been invited to. With external access (federated chat), the external chat participants have no access to the inviting organization’s teams or team resources. They can only participate in one-on-one federated chat. Tenant admins can choose between the two communication options depending on which level of collaboration is desirable with the external party. Admins can choose either approaches or both, depending on their organizational needs, but we recommend enabling guest access for a fuller, collaborative Teams experience.
For a detailed comparison, see Manage external access.
Review guest access periodically
In Teams, you can add 5 guests for each licensed user. Because of this limitation, or because you want to keep your tenant up to date, you should review guest access periodically to identify users who have access that they don't need anymore. You can use Azure AD to create an access review for group members or users assigned to an application. Creating recurring access reviews can save you time. If you need to routinely review users who have access to an application or are members of a group, you can define the frequency of those reviews.
You can perform a guest access review yourself, ask guests to review their own membership, or ask an application owner or business decision maker to perform the access review. You use the Azure portal to perform guest access reviews. For more information, see Manage guest access with Azure AD access reviews.
Access reviews are available with the Premium P2 edition of Azure AD, which is included in Microsoft Enterprise Mobility + Security, E5. For more information, see Azure Active Directory editions. Each user who interacts with this feature by creating a review, filling out a review, or confirming their access, must have a license.
Teams doesn't restrict the number of guests you can add. However, the total number of guests that can be added to your tenant is based on what your AAD licensing allows. For more information, see Azure AD B2B collaboration licensing.
Guest access latencies
The guest settings are set in Azure AD. It takes 2 hours to 24 hours for the changes to be effective across your Office 365 organization. If a user sees the message "Contact your administrator" when they try to add a guest to their team, it's likely that either the guest feature hasn't been enabled or the settings aren't effective yet.
For information about using PowerShell to manage guest access, see Use PowerShell to control guest access to a team.