Microsoft 365 Down? Outage: Teams, Outlook And OneDrive Disruptions Persist Into A Third Day For Users

A widespread outage affecting Microsoft 365 stretched into its third day this week, with users of Outlook, Teams, SharePoint and OneDrive for Business continuing to report intermittent access problems even as Microsoft said the vast majority of the disruption had been resolved.

The outage, which Microsoft is tracking internally under the incident number MO1465074, began at 3:08 p.m. UTC on Monday, Aug. 31, according to the company. Microsoft attributed the root cause to a problem within a core authentication configuration shared across multiple Microsoft 365 services, rather than an issue isolated to any single product.

"The root cause of the outage is an issue within a core authentication configuration used by multiple Microsoft 365 services," the company said in a status update, adding that the disruption had triggered a broader service degradation designation for Microsoft 365 Business and Enterprise customers.

Outlook was among the first and most visibly affected services, with users reporting delays and outright failures in sending and receiving email, along with authentication errors and problems searching mailbox content. User reports on the crowdsourced outage-tracking site Downdetector began surging around 11:30 a.m. ET on Monday and had climbed past 5,000 by early afternoon, with additional complaints flooding social media platforms throughout the day.

Microsoft said its investigation initially pointed to a misconfiguration affecting how authentication components were deployed across a portion of its infrastructure.

"Our investigation indicates that a misconfiguration issue may be preventing authentication components from deploying as expected to a portion of infrastructure, and we're reexamining recent changes made to the service to determine why this is occurring," the company said in an update posted to its Microsoft 365 Status account.

As the outage continued into Monday evening, Microsoft confirmed that its impact extended well beyond Outlook and Exchange Online, the email and calendaring backbone used by millions of businesses. The company said OneDrive for Business, SharePoint Online, Microsoft Teams, Microsoft Purview and Microsoft Defender XDR were also affected, along with the Microsoft 365 Admin Center and Universal Print.

"Additionally, we've confirmed that the authentication component issue impacts other services beyond Exchange Online," Microsoft said, directing customers to its status page for details on the specific ways each affected service was behaving.

By Tuesday, the outage had not fully resolved, prompting Microsoft to continue publishing incremental updates as engineers worked through a remediation process that included restarting affected infrastructure and reapplying a targeted fix to the authentication systems at the center of the problem.

"Our mitigation actions are continuing to progress within the remaining affected infrastructure," Microsoft said in a Tuesday update. "Indications from telemetry remain positive, and we've confirmed service availability is improving. We're entering a period of extended monitoring to ensure a full resolution is in place."

The company's messaging throughout the incident emphasized gradual, uneven recovery rather than a single clean fix, a pattern consistent with prior large-scale Microsoft 365 outages that have often required extended monitoring periods even after initial telemetry data showed improvement.

By early Wednesday morning, Microsoft indicated that conditions had stabilized significantly for most customers.

"Service availability remains stable above 99 percent," Microsoft said in a status update posted at 6:29 a.m. ET Wednesday, adding that "the majority of users should no longer be seeing impact from this issue."

Even so, scattered reports of ongoing trouble continued to surface into Wednesday, including separate tracking on outage-monitoring sites showing renewed spikes in complaints specifically tied to Microsoft Teams, suggesting that while the broader authentication issue had largely subsided, some customers and services continued to experience residual effects.

Microsoft 365, the cloud-based subscription suite formerly known as Office 365, provides access to core productivity applications including Word, Excel, PowerPoint, Outlook and Teams, along with enterprise-focused services such as SharePoint and OneDrive that many businesses rely on for document storage, collaboration and internal communication. Because so many organizations depend on these tools for day-to-day operations, outages affecting the platform tend to generate an outsized wave of public complaints and business disruption relative to their technical scope, particularly when authentication systems are involved, since login failures can lock users out of multiple services simultaneously rather than affecting a single isolated feature.

This week's incident adds to a string of significant Microsoft 365 disruptions in 2026. In January, a separate outage tied to authentication and mail-flow problems in North American infrastructure stretched for roughly ten hours, affecting Outlook, Defender and Purview before Microsoft confirmed the impact had been resolved. At the peak of that earlier incident, outage reports on Downdetector topped 15,000, with some affected businesses describing significant disruption to daily operations, including delayed communications with clients.

Independent monitoring services that track Microsoft 365's uptime over time have noted that the platform has experienced a handful of major disruptions each year in recent years, with durations typically ranging from a few hours to, in more severe cases, closer to a full day. Analysts who study cloud infrastructure reliability have pointed to the increasing complexity of large, interconnected cloud platforms as a persistent challenge for major providers, even as those same companies continue investing heavily in redundancy and failover systems designed to prevent exactly this kind of widescale service degradation.

Microsoft has not yet published a full post-incident report detailing the underlying technical root cause of this week's authentication misconfiguration or outlining specific steps the company plans to take to prevent similar disruptions in the future. Such detailed retrospectives typically follow major outages after monitoring periods conclude and engineering teams complete a full review of the incident.

For now, Microsoft has continued to direct affected customers to its official Microsoft 365 Status page and social media account for the most current information as monitoring continues, while cautioning that some users may still experience intermittent effects even as overall service availability holds above the 99% threshold the company reported Wednesday morning.