Microsoft Outlook sign-in outage

Microsoft said Outlook.com suffered a worldwide sign-in outage on Monday, April 27, that signed some users out and blocked mailbox access. (bleepingcomputer.com) The company said affected users saw intermittent login failures, “too many requests” errors, and unexpected sign-outs as reports spread through the morning. (bleepingcomputer.com) (cnet.com) BleepingComputer reported the incident had been underway for more than three hours by 8:03 a.m. Eastern, and Microsoft later said service returned to normal about 10 hours after the outage began. (bleepingcomputer.com) Microsoft told users during the outage that its investigation pointed to client sign-in scenarios, then said at 9:46 a.m. Eastern that it was reverting a “recently introduced change.” (bleepingcomputer.com) (cnet.com) The problem hit a service people use as the front door to email: if authentication fails, messages can still exist on Microsoft’s servers while users cannot open their inboxes. (bleepingcomputer.com) Microsoft classified the event as “service degradation,” the label it uses when an incident causes noticeable customer impact without taking the service fully offline for everyone. (bleepingcomputer.com) Even after Microsoft said telemetry showed the service was healthy again, some iPhone users still had to re-enter their passwords in Apple’s Mail settings to restore access. (cnet.com) (bleepingcomputer.com) Downdetector reports began climbing just before 5 a.m. Eastern, and CNET said complaints peaked at about 1,500 early in the day. (cnet.com) The outage followed other Microsoft email disruptions in March and April, including Exchange Online incidents that blocked mailbox access for some Outlook users. (bleepingcomputer.com 1) (bleepingcomputer.com 2) By late Monday, Microsoft’s public message had shifted from investigation to recovery, but the cleanup still required some users to sign back in by hand. (bleepingcomputer.com) (cnet.com)