Have you been trying to send an important work email, edit a crucial presentation, or access your cloud-stored documents, only to find yourself staring at an error message? You’re not alone in this, as that’s the frustrating reality for hundreds of users worldwide who are experiencing a major Microsoft 365 outage of service.

The tech giant confirmed the outage through its official Microsoft 365 Status account, acknowledging that some users were unable to access web-based apps. The problem primarily affected popular services like Outlook, OneDrive, and other Office web applications, leaving many professionals disgruntled.

Microsoft revealed it was investigating issues within its authentication infrastructure, specifically focusing on “token generation” – the digital handshake that allows users to access their cloud services. While the company worked behind the scenes, affected users were greeted with a somewhat reassuring message: “We’re experiencing a service outage. All of your open files have been saved.”

We’re investigating an issue where some users may be unable to access Microsoft 365 apps for the web. We're reviewing service monitoring telemetry to isolate the root cause and develop a remediation plan. For more information, please refer to OO953223 in the admin center.

— Microsoft 365 Status (@MSFT365Status) December 10, 2024

This isn’t the first time Microsoft has faced such widespread service disruptions. Just two weeks ago, a similar outage impacted multiple services, including Microsoft Teams, Exchange Online, and SharePoint, lasting over 24 hours. Even more significant, a July incident was triggered by a distributed denial-of-service (DDoS) attack that exposed vulnerabilities in the company’s protection mechanisms.

For now, those caught in the current outage are being advised by Microsoft to use desktop applications. Users with the appropriate licenses have been advised to switch to desktop versions of their Microsoft 365 apps while the company works on resolving the issue.