What's Happening
Microsoft Outlook users globally are experiencing widespread login issues and service disruptions. Starting around 5 a.m. ET on Monday, April 27, users began reporting problems accessing Outlook.com and the iOS mobile app. Microsoft confirmed on its official service status page that some users are experiencing intermittent sign-in failures, receiving 'too many requests' errors, and being unexpectedly signed out of their accounts.
Root Cause
Microsoft has not identified a specific root cause but is investigating an unexpected increase in error rates affecting two separate error scenarios. The company stated it is reviewing a recent change as part of its ongoing investigation. Microsoft noted that reverting a recently introduced update did not alleviate the login issues, indicating the problem may be more complex than a simple faulty update.
Affected Services and Users
The outage impacts Microsoft 365 Business and Enterprise customers, Outlook.com users, and users of the iOS Outlook app. While iOS users are particularly affected, Microsoft stated the errors are not limited to iOS devices. Mobile users reported being signed out of the Outlook app on their iPhones with login attempts returning 'too many requests' error messages.
Scale of the Outage
The outage has affected users globally with significant impact. By 9:38 a.m. ET on Monday morning, DownDetector recorded over 1,200 error reports, with the spike beginning around 5 a.m. ET. Microsoft users expressed frustration on social media about both the service interruption and the lack of transparent communication from Microsoft.
Microsoft's Response
Microsoft acknowledged the issue on its official status pages and directed users to its X (Twitter) account for updates. The company stated it is analyzing service telemetry, investigating the unexpected error rate increase, and determining next steps and mitigation actions. As of the latest updates, the outage remained ongoing with no resolution announced. 
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