Microsoft’s cloud services, including Outlook and Exchange Online, experienced a significant outage affecting tens of thousands of users starting around 18:00 UTC on Thursday, November 12. The company reported issues with servers failing automated health checks, resulting in service unavailability. As of Friday, Microsoft was still working to restore functionality but had not specified a timeline for full recovery.
The outage began with email disruptions, which were followed by issues with Microsoft Teams. By 1 PM Eastern time, around 130,000 outage reports were logged on Downdetector, with users unable to send or receive emails or access their inboxes. Combined reports from Canada and the U.S. peaked at nearly 150,000 by 1:30 PM, before declining to over 35,000 by 9:30 PM.
Microsoft’s initial response came via its 365 Status account on X, acknowledging the issues impacting the ability to reach Exchange Online mailboxes through multiple connection methods in the Americas. A company spokesperson later indicated to CNBC that the primary issues stemmed from Exchange Online, affecting users across all regions.
In addition to Exchange Online, services affected included Teams, SharePoint Online, and Microsoft Intune, as well as security services like Defender XDR and Microsoft Purview. The outage had far-reaching implications, impacting public services such as hospitals in Canada and Via Rail’s email system for passenger communications.
Microsoft’s explanation of the outage evolved as the incident progressed. Initially attributing the issue to elevated load, the company later clarified that server failures were responsible, which overwhelmed remaining operational servers. According to Microsoft, the failures were linked to automated health checks, and attempts to validate an alternative health check method were met with complications.
Despite ongoing investigations, Microsoft stated it had found no evidence of a cyberattack, but no root cause had been established. A recent post-incident review had yet to be conducted.
The incident raised awareness of the importance of continuity planning among organizations relying on Microsoft 365. With invoicing, approvals, and internal communications disrupted, organizations were reminded to document service outages and communications, and to have contingency plans that do not rely solely on Microsoft’s platforms for critical notifications.
As Microsoft continues its efforts to restore full service, questions remain about the underlying causes of the failure and whether such outages could recur in the future.
