Overview
- User reports of Outlook failures spiked on Monday, Aug. 31, with outage trackers showing thousands of reports of login failures, delayed or missing messages, and web errors.
- Microsoft logged the incident as EX1464935 and traced the problem to a core authentication configuration that prevented authentication components from deploying correctly across parts of its infrastructure.
- Users reported specific symptoms such as emails stuck in Sent, OWA returning 500 errors, inboxes and subfolders failing to load, and mailbox search returning incomplete results.
- Microsoft tested a remediation on a portion of its environment, began broader rollouts after positive results, said mail flow is gradually recovering, and moved into extended monitoring while some search and dependent features remain degraded.
- The outage produced tens of thousands of public reports and briefly affected other Microsoft 365 services including Teams, OneDrive, SharePoint and Defender XDR, creating workplace disruption and prompting admins to watch EX1464935 and related status updates.