Major Microsoft 365 outage left users without access to emails and files - here's what we know

• MO1221364 Microsoft 365 outage has now been fixed
• Microsoft says parts of its North America infrastructure were to blame
• Hours of rebalancing and refining preceded a fix, but it seems to have worked

A widespread Microsoft outage disrupted access to core M365 services for enterprise customers, as email inboxes, files, meetings and other cloud-based tools were all being limited.

"We're investigating a potential issue impacting multiple Microsoft 365 services, including Outlook, Microsoft Defender and Microsoft Purview," the company wrote in an X post, identifying the issue as MO1221364 within the admin center.

Regular X updates throughout the outage confirm a fix was issued around 12 hours later, bringing affected services back online, and we now know what the problem was.