Thousands of Microsoft enterprise customers encountered difficulties accessing email and other workplace tools on Monday as employees returned from the weekend. Reports first appeared on social media and outage-tracking platforms, where users described problems with Microsoft Outlook. Microsoft later confirmed that the disruption extended beyond Outlook and affected several cloud-based business services.
At 12:01 p.m. Eastern Time, Microsoft said Exchange Online service had been disrupted. Exchange Online provides organizations with cloud-based email, calendar, contacts, and task management. In a separate statement, a company spokesperson acknowledged that customers were unable to access Exchange Online and some related services. The spokesperson said Microsoft understood the disruption and was working to restore access as quickly as possible.
Microsoft’s official status page classified the incident as “service degradation” for Microsoft 365 Business and Enterprise customers. The listed services included OneDrive for Business, SharePoint Online, Exchange Online, Microsoft Teams, Microsoft Purview, Microsoft Defender XDR, and the Microsoft 365 Admin Center. Because the administrative portal was among the affected products, some administrators may have faced difficulty viewing official incident notices. Microsoft directed administrators to advisories MO1465074 and EX1464935 for detailed updates.
Microsoft attributed the outage to a problem involving a core authentication configuration shared by multiple Microsoft 365 services. This type of shared infrastructure issue can affect several products at once because users and administrators rely on common systems to verify access. The company said it was testing a remediation strategy while reviewing recent service changes to identify the problem’s source.
As of Microsoft’s 6:01 p.m. Eastern Time update, the company had not announced full restoration. It said engineers were continuing to examine recent changes and seeking definitive confirmation of the cause. The disruption affected business communications, collaboration, security, storage, and administration functions, leaving organizations dependent on Microsoft 365 awaiting further updates and service recovery Monday evening.