The provided text consists of Microsoft 365 Service Updates for the week of September 15–21, 2025, detailing numerous upcoming changes and retirements across the platform. Several announcements focus on Microsoft Teams, including increased limits for private channels, new external access controls by domain, and the transition from Live Events to Teams Town Hall. Other significant updates address security and compliance, such as the deprecation of legacy TLS cipher suites and the end of support for Office 2016 and 2019 products on October 14, 2025. Finally, there is a strong emphasis on AI and Copilot integration, with new features rolling out to Viva Insights, PowerPoint, and SharePoint, alongside the introduction of AI-powered agents and related administrative controls.