Microsoft 365 outage hits Defender, Outlook, Teams users
Microsoft’s 365 enterprise platform, including its Microsoft Defender security solutions and Microsoft Purview data management suites, is experiencing outages affecting thousands of users, reportedly due to a third-party networking issue.
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Microsoft 365 users across North America lost access to Outlook, Teams, Defender, and admin services during Thursday’s outage.
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While most services are back online, Microsoft says some users may still experience intermittent disruptions as systems stabilize.
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The disruption shows how a single network failure can quickly affect millions of people who rely on cloud services to work and communicate.
The productivity software suite began having issues at about 2:00 p.m. Eastern Time on Thursday, according to the internet outage monitoring site Downdetector.com.
Microsoft quickly issued several statements on X indicating that IT teams were investigating a “potential issue impacting multiple Microsoft 365 services, including Outlook, Microsoft Defender, and Microsoft Purview.”
The company also directed users to its Service Health Status page to follow updates.
According to the status page, Microsoft described the root cause as “a portion of dependent service infrastructure in the North America region not processing traffic as expected.”
The issue is said to be largely resolved, though some users are expected to experience continued intermittent disruptions across North America. Microsoft did not identify the "third-party."
“Users may be seeing degraded service functionality or be unable to access multiple Microsoft 365 services,” Microsoft said in its latest update about 6:00 p.m. ET.
Affected services include:
- Various e-mail functions for Exchanges, including Microsoft Viva Engage and Microsoft Fabric users, Outlook.
- SharePoint Online, Microsoft OneDrive, and/or Microsoft Teams search function.
- Accessing service portals, including Microsoft Purview, Microsoft Defender XDR, Microsoft 365 admin center.
- Microsoft Teams various functions and live events
- Print registration and printer jobs may fail in Universal Print.
Several thousand users also reported having issues connecting and logging in to the Microsoft Store, including for both desktop and app versions, Downdetector showed.
Even with issues mostly resolved, 365 users took to social media expressing dismay at the disruption lasting throughout the day, some even blaming AI for the chaos.
"Five hours later, and I've gotten 3 total emails. None of my test messages from different Gmail and consumer Microsoft accounts have come in yet. Most admin portals still won't load. What a mess. Stop cramming AI into everything and prioritize uptime for all services!!" one user wrote.
Outage spikes across North America
Microsoft initially posted at 12:41 ET that the widespread issues were due to “a third-party networking issue affecting access to Microsoft 365 services, including Teams and Outlook.”
By close of business day, Microsoft said the affected infrastructure has been returned to a healthy state but that “further load balancing is required to mitigate impact.”
“We're carefully rebalancing traffic across all affected infrastructure in the region, while monitoring the corresponding health telemetry, to ensure the environment enters into a balanced state as our remediation efforts continue,” it said.
At its peak, more than 30,000 outage reports were logged around 3:15 p.m. ET, with about two-thirds of Microsoft 365 users reporting problems with Microsoft Exchange, the company’s enterprise email and calendar platform.
Downdetector also showed over 80% of Outlook users reported trouble receiving messages, while a small percentage experienced issues with the app and website.
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Another 30% of users – primarily IT administrators and support staff – reported problems accessing the Microsoft 365 Admin Center, where teams manage apps, services, devices, data, and users across enterprise subscriptions.
While Downdetector does not monitor Microsoft’s security software separately, Microsoft Defender for Individuals includes its anti-malware, web, and identity theft protection suite, while its cloud-based endpoint detection security software is geared towards enterprise customers.
Microsoft Purview, its data security and governance platform, safeguards business-critical data while helping companies ensure proper compliance with data-handling requirements.
Microsoft’s day-long disruption to Microsoft 365 marks the first major outage of 2026 and serves as an unfortunate reminder of how many organizations now depend on just a handful of vendors for their software, networking, and security needs.
Last October, an Amazon Web Services (AWS) outage left companies scrambling for nearly 24 hours after a DNS issue forced hundreds of apps and websites to go offline, impacting millions of users.
Weeks later, a technical issue caused networking giant Cloudflare to go down, leaving hundreds of millions of people across the globe unable to access the internet.
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