The primary failure involved users being unable to access Exchange Online mailboxes through multiple connection methods. Microsoft identified the root cause as a core process on affected servers becoming overwhelmed, which caused the servers to stop responding and contributed to a loss of capacity. This overload led the servers to fail during automated health checks, rendering them “unexpectedly unavailable” and exacerbating the connectivity errors. The disruption extended beyond email, with thousands of users reporting issues with Microsoft Teams, OneDrive, Copilot, and the Microsoft Store, though Microsoft noted that Teams issues in North America had been successfully restored earlier in the day.
In response, Microsoft paused all deployments and moved additional traffic off the affected infrastructure. The company stated it was “aggressively pursuing all pathways to reduce impact” by restarting affected servers and isolating portions of its service infrastructure. By 4 p.m. ET, Microsoft reported making progress by validating an alternative service health check method, which allowed a subset of affected servers to return to service. The company is now applying this change more broadly and preparing automated recovery systems to continually detect and restart unresponsive servers to maintain stability.
Despite these measures, the Outlook platform remained down for most users as of 8:15 p.m. ET. Microsoft acknowledged that initial actions had not provided the anticipated relief, noting that it is analyzing traffic patterns across its entire service infrastructure. The company is evaluating whether isolating traffic within specific regions may allow affected areas to recover independently.
This outage highlights the critical dependency of global enterprise operations on Microsoft 365 infrastructure. As of the latest updates, Microsoft continues to work on mitigating the impact, with no confirmed timeline for full service restoration provided in the source materials.
