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Microsoft is investigating an ongoing service degradation affecting Outlook.com that has resulted in intermittent sign-in failures for users since before 5 a.m. ET on Monday. The company has identified a recent configuration change as the likely cause and is in the process of reverting that change to restore full service.
User Impact
Users attempting to access their email accounts have reported being unexpectedly signed out or encountering "too many requests" errors. According to outage tracking service Downdetector, the number of user complaints peaked at approximately 1,300 reports. By 3:47 p.m. ET, that number had decreased to around 1,000 reports. The issue has affected sign-in on both web browsers and mobile applications.
Official Statement and Investigation
On Microsoft's Service Health Status page, the company stated: "Some users may experience intermittent sign‑in failures, including 'too many requests' errors or unexpected sign‑outs." The company added that its investigation "indicates client sign-in scenarios may be contributing to the reported behaviour."
In a subsequent update posted at 09:46 EDT on April 27, Microsoft stated:
"We're reverting a recently introduced change to determine if this action provides relief from impact upon completion. In parallel, we're continuing to analyze customer reports, and we're closely monitoring service telemetry to identify our next steps."
A Microsoft spokesperson confirmed that internal logs link the issue to a recent configuration change, which has been rolled back. The company is monitoring the environment to assess whether the rollback is effective.
Status and Root Cause
The incident has been classified by Microsoft as "service degradation." The company has not disclosed the specific root cause of the configuration change, the number of users affected, or the regions impacted.
Context
Last month, Microsoft mitigated a separate Exchange Online outage that blocked users from accessing mailboxes and calendars via various protocols. On the same day, the company addressed another issue causing sign-in problems for Office.com and Microsoft 365 Copilot web.