Outlook on the web's activity-based timeout (ABT) will retire by January 2026 (February for GCC/DoD). Admins must enable Microsoft 365 idle session timeout for consistent session control across apps. Users won't auto-sign out without it. Prepare by reviewing ABT use, enabling the new timeout, and updating documentation.
Applies to: Exchange Online · Microsoft 365 for the web
Source: mc.merill.net — data via Merill Fernando's open archive (MIT).