Updated at 11:00 p.m. CT: Microsoft states that its mailbox connectivity should now have returned to normal, though it continues to work on restoring search functionality. The company stated that it may also take a while for backlogged mail queues to clear "due to the volume of previously queued messages."
Updated at 9:15 p.m. CT: Microsoft has offered an update on its ongoing efforts to restore Microsoft 365's services, stating that its "recovery efforts are ongoing." Users should see email delivery gradually come back online, however Microsoft warns that its search feature is still experiencing issues.
"We're closely monitoring the health of the service environment amidst our ongoing recovery work, and we're observing some sections of affected infrastructure which aren't accepting the re-applied authentication components as readily as expected. Users can expect to see continued recovery to email delivery, while users may see residual impact to downstream and dependent scenarios, including search, across affected services. We're working to identify whether any additional actions are required to expedite full recovery."
Updated at 7:09 p.m. CT: Microsoft had an update on Monday evening, saying a "gradual recovery to mail flow" was in the works.
"We're continuing to deploy our mitigation across the affected environment and users should begin to see gradual recovery to mail flow. In parallel, we're restarting targeted sections of the affected infrastructure to aid the recovery of the downstream scenarios. For more information, please see EX1464935 and MO1465074 in the admin center."
Updated at 4:53 p.m. CT: In a statement provided to Mashable through email, a Microsoft spokesperson issued the following statement:
"We're aware of an issue affecting access to Exchange Online and some other services. We know this is disruptive for customers and we appreciate their patience while we work to restore services as quickly as possible."
Updated at 4:19 p.m. CT: Microsoft has offered a more specific explanation for what's driving the ongoing disruption. In its latest update, the company said its investigation suggests a "misconfiguration issue" is stopping authentication components from deploying correctly to part of its infrastructure.
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In plain terms, it means an internal change to Microsoft's authentication system caused parts of it to fail to perform properly. Now, engineers at Microsoft are retracing those changes to pinpoint the cause.
Updated at 3:47 p.m. CT — Starting on Monday morning and continuing into the afternoon, thousands of Microsoft business users reported problems with Microsoft Exchange Online (the issues were first reported as an Outlook outage). Now, Microsoft's official service health status page has been updated to reflect what users have been saying for hours: this outage extends well beyond Microsoft Exchange Online.
At the time of writing, Microsoft's status page now lists a broader "service degradation" affecting Microsoft 365 for both Business and Enterprise customers. The updated list of impacted services includes OneDrive for Business and SharePoint Online, Exchange Online, Microsoft Teams, and both Microsoft Purview and Microsoft Defender XDR.
The company says it's continuing to test its mitigation strategy to ensure the planned fix doesn't introduce new problems, while also exploring other ways to reduce the impact in the meantime. Admins and enterprise customers can find more information by looking up EX1464935 and MO1465074 in the admin center.
Previously, the status page showed these services as operating normally, even as Microsoft acknowledged a problem on X. Meanwhile, users took to social media and Reddit to complain of widespread login failures, missing emails, and inaccessible files. Microsoft Azure and consumer-facing Microsoft products appear to be unaffected at this time.
Microsoft Outlook appears to be down for a significant number of users as of Monday late morning. According to Downdetector, reports of Outlook problems spiked sharply just before 11:16 a.m. ET, jumping from around 37 reports to over 6,000 in a short window.
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Of the issues users are reporting, the largest share involves receiving messages, followed by app-related problems and login issues, per Downdetector's tracking. While most users are complaining about Outlook problems, Microsoft acknowledged a problem with Microsoft Exchange Online on its Microsoft 365 Status account on X. Exchange Online is "a cloud based messaging platform that delivers email, calendar, contacts, and tasks."
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The company stated it was investigating reports of Exchange Online issues, pointing users to incident EX1464935 in the admin center for updates.
About an hour later, Microsoft followed up to confirm the scope of the problem, saying it had verified that users may be experiencing degraded functionality across various Exchange Online features. The company said it was reviewing service telemetry and diagnostic data to pin down the root cause.
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At the time of this writing, Microsoft's status account posted a more specific update, stating it had identified an issue with an authentication component that contributed to the disruption. According to the post, Microsoft has “developed a remediation strategy” and is testing it to confirm it resolves the impact before rolling it out more broadly. However, as of this writing, Microsoft's Service Health Status page says that all its products are "currently operational."
The outage has stirred up plenty of frustration online. On X, users have pushed back on Microsoft's "degraded functionality" language, with one commenter calling it "one way to say 'none of our shit works.'"
Others reported the disruption stretching on for hours, with entire offices and thousands of employees affected worldwide, according to posts under Microsoft's status updates.
A parallel Reddit thread in r/Outlook saw a similar flood of confirmations from users locked out of the service, with dozens simply chiming in with variations of "down for me" and "yep, whole company having issues."
This is a developing story...