Microsoft 365 / Office 365 Outage 11/12/2026

Microsoft 365 / Office 365 Outage – November 12, 2026

Article ID: KB-M365-2026-1112
Status: Active – Partial Recovery Underway (as of ~7:30 PM CST / 8:30 PM ET)
Severity: High – Multi-service impact
Last Updated: November 12, 2026, 7:34 PM CST

** This outage did not affect DNS Texas hosted email services **

Summary

On Thursday, November 12, 2026, Microsoft experienced a widespread service degradation affecting Microsoft 365 (Office 365). Users reported inability to access Outlook / Exchange Online mailboxes, Microsoft Teams, SharePoint Online, Microsoft 365 Copilot, Microsoft Defender XDR, and other related services. The incident began in the late morning Eastern time, peaked in the early afternoon, and remained under active remediation into the evening with partial recovery observed.

Microsoft tracked the issues under incident IDs EX1550543 (Exchange Online) and MO1550821 (broader Microsoft 365 suite). The public status page continued to show “Service degradation” as of the evening of November 12.

Affected Services

• Exchange Online / Outlook (primary impact – mailbox connectivity)
• Microsoft Teams
• SharePoint Online
• Microsoft 365 Copilot
• Microsoft Defender XDR
• Microsoft Planner and To Do
• Additional reported impacts included some Purview services, Power BI PDF export with sensitivity labels
• Microsoft 365 Apps Admin Center features
• Intermittent OneDrive / Office Online access.

Impact was initially reported in the Americas and later expanded to potentially any region. Both enterprise/business tenants and some consumer accounts were affected.

Timeline (Eastern Time)

• Around 11:17 a.m., impact start was recorded for EX1550543 (Exchange Online mailbox connectivity).
• Around 12:54 p.m., Microsoft publicly acknowledged that it was investigating Exchange Online mailbox access issues in the Americas.
• Between roughly 1:00 and 1:20 p.m., user reports on Downdetector peaked at approximately 130,000–138,000 Outlook reports.
• From about 1:07 p.m. onward, the scope expanded and the issue was described as potentially affecting Microsoft 365 connectivity for users in any region. The broader incident MO1550821 was opened.
• Throughout the afternoon, Microsoft identified that the elevated load resulted from servers becoming unexpectedly unavailable after failing automated health checks (not from increased traffic). Deployments were paused, traffic was shifted, and server restarts were initiated.
• Between approximately 4:00 and 6:00 p.m., an alternative health-check method was validated and applied more broadly. A portion of servers were returned to service and remained stable. Limited recovery was observed.
• Into the evening (through roughly 8:30 p.m. ET), partial recovery continued with reports declining. Some restored servers remained susceptible to becoming unresponsive under traffic. Configuration and network changes were under review or reversion. The status page still showed Service degradation.

Cause

According to Microsoft’s service health updates, a large number of servers became unexpectedly unavailable after failing automated health checks. This created elevated load on the remaining infrastructure and was explicitly not caused by an increase in user traffic.

Later investigation pointed to issues with a component responsible for processing server health checks and a process for establishing secure connections that could become overwhelmed. Microsoft was reviewing and, in some cases, reverting recent configuration and network changes that correlated with the start of impact.

As of the evening of November 12, 2026, Microsoft had not published a full root-cause analysis. There was no indication or evidence of a cyberattack.

Current Status and Resolution

• As of approximately 7:30 PM CST (8:30 PM ET) on November 12, 2026, the Microsoft 365 status page (status.cloud.microsoft) showed Service degradation for Business or Enterprise.
• A portion of affected servers had been returned to service and had remained stable. Traffic had been shifted to alternate routes where possible, and limited recovery had been observed in some regions. User reports on Downdetector had declined substantially from the afternoon peak but remained elevated.
• Recovery was gradual as client applications reconnected. Some servers could become unresponsive again once they received traffic.
• Microsoft continued to apply alternative health-check methods, restart unresponsive servers, and refine recovery processes. No estimated time of full restoration had been provided.
• Recommended Actions for DNS Texas Customers
• Do not reset passwords, remove and re-add accounts, or reinstall Outlook/Teams clients. This is a Microsoft-side issue.
• Monitor the official Microsoft 365 status page at https://status.cloud.microsoft/
• Microsoft 365 administrators should check Service health in the admin center for incidents EX1550543 and MO1550821 (or use the public status page if the admin center is inaccessible).
• Users may experience intermittent or gradual recovery. Retry access periodically. Local/cached content in Outlook desktop may still be available for offline use.
• For time-sensitive communications, use alternative methods (phone, SMS, or other email systems) until full service is restored.

References And Official Sources

• Microsoft 365 Service Health: https://status.cloud.microsoft 
• Microsoft 365 Admin Center → Health → Service health (incidents EX1550543 and MO1550821)
• Downdetector and major news outlets (Reuters, BleepingComputer, USA Today, The Guardian, and others) provided corroborating user-report volume and timeline details.

Disclaimer

This article is based on publicly available information from Microsoft service health updates and reputable news sources as of the evening of November 12, 2026. Microsoft is the authoritative source for the current status and final root cause. Information is subject to change as the incident progresses.