Microsoft scrambled to fix widespread email outages Thursday that left thousands of users unable to send or receive messages through Outlook during peak business hours.
The problems started around 2:37 p.m. ET Thursday. Users attempting to access Outlook received “451 4.3.2 temporary server issue” error messages.
The timing couldn’t have been worse. Schools, government offices, and companies across the United States struggled to communicate as the outage hit during the workday.
#BREAKING Microsoft is experiencing a major outage right now!
Thousands of users are reporting issues with Microsoft 365 services, including:
– Outlook (email sending/receiving blocked, error codes like 451 4.3.2)
– Teams
– Exchange
– Microsoft Defender
– Microsoft Purview
– And… pic.twitter.com/npcBnvcMbm— Breaking News (@TheNewsTrending) January 22, 2026
Microsoft confirmed the issues on X. The company said it was investigating problems affecting multiple Microsoft 365 services.
Outlook wasn’t the only casualty. OneDrive cloud storage searches ran slow or failed completely.
Teams users couldn’t create chats, meetings, channels, breakout rooms, or live events. SharePoint Online also experienced disruptions.
Microsoft Defender and Microsoft Purview joined the list of affected services. All these tools form the backbone of Microsoft’s productivity software bundles.
By 3:17 p.m. ET, Microsoft pinpointed the culprit. A portion of service infrastructure in North America wasn’t processing traffic correctly.
The company started routing traffic to alternate infrastructure to support recovery. Microsoft also began load-balancing efforts to restore service.
At 4:14 p.m. ET, Microsoft said it had restored affected infrastructure. The company was directing traffic elsewhere to speed up recovery.
But the fix wasn’t quick. Service remained degraded more than seven hours after Microsoft first acknowledged the errors.
“We’re seeing continued improvements in service availability and functionality as a result of our load-balancing efforts,” Microsoft posted at 9:46 p.m. ET. The company continued monitoring performance and making adjustments through the night.
Downdetector tracked the chaos. Over 15,890 users reported issues at the peak of the outage.
Users took to social media to vent frustrations. The disruption highlighted how dependent businesses have become on Microsoft’s cloud services.
By Friday morning, Microsoft declared victory. The company confirmed all affected infrastructure had been restored to a healthy state.
Downdetector showed the recovery in real-time. Incident reports plummeted to just 113 by 1:05 a.m. ET Friday.
Microsoft said the impact had been resolved. The company successfully routed traffic back to normal channels after fixing the problematic North American infrastructure.
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