Major Microsoft 365 outage left users without access to emails and files – here’s what we know | Daily Reports Online
- 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.
M365 outage is now fixed
The company blamed “a portion of service infrastructure in North America” for “not processing traffic as expected.” Although the precise cause was not fully disclosed, the identification came around an hour after Microsoft first shared reports of the outage.
“Any users served through an affected section of service infrastructure in the North America region may be intermittently impacted,” the status read.
Affected users were seeing a “451 4.3.2 temporary server issue” error message.
Some of the remedial steps Microsoft took between identifying the issue and fixing it were “rebalancing traffic across all affected infrastructure,” refining this to “optimize performance” and restoring services to a “healthy state.” The issue has since been fully resolved.
Downdetector data roughly corroborates this, showing a spike at the time of identification. Two-thirds of the issues related to Exchange access, with some users reporting issues with server connections and logging in. A separate spike correlates with the fix – it’s unclear if this is related to changes made to issue the fix, or if the second spike is indicative of another outage.
At the time of writing, Microsoft’s status page shows no further sign of issues.
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