Overview

• The outage began at 22:20 UTC on July 9 when users worldwide lost access to Outlook mailboxes across desktop, web and mobile platforms
• Microsoft identified a malfunctioning authentication component within its mailbox infrastructure as the root cause of the disruption
• On July 10 Microsoft deployed configuration changes in stages, achieving full service health by 17:25 UTC after faster-than-expected rollout
• Downdetector data showed peak reports with over 62% of users unable to log in, 33% facing server connection errors and 5% blocked from sending emails
• Outlook, which serves more than 400 million users globally, is now operating normally with no further interruptions reported