external guests

External guests in Microsoft Teams are a key concern for IT administrators, security teams, and compliance officers, especially following Microsoft's introduction of email-to-chat functionality. This feature automatically provisions external email recipients as guests in the sender's tenant, governed by Entra B2B guest controls. The change, enabled by default and rolling out in stages from November 2025, requires proactive policy management to control guest access and maintain compliance. Administrators can opt out using Teams messaging policies. Discussions on WindowsForum cover the implications of this update, including how to govern external guests effectively and ensure security and compliance within Teams environments.