A multi-day outage affecting Microsoft 365 and Outlook continued into Tuesday, September 1, 2026, with the company reporting ongoing improvements but stopping short of declaring a full resolution.
The disruption began when an issue with Microsoft’s Exchange Online service caused email delays and failures, authentication problems, and other service degradations for Outlook users. Microsoft’s status page later confirmed that the problems extended beyond Outlook to include SharePoint, Copilot, Teams, Purview, Defender XDR, the Microsoft 365 Admin Center, and Universal Print — all attributed to a fault in a “core authentication configuration used by multiple Microsoft 365 services.”
Overnight, Microsoft identified the root cause as a misconfiguration that was preventing authentication components from “deploying as expected to a portion of infrastructure.” The company reviewed recent changes, then tested and implemented a series of mitigations aimed at restoring service for end users.
Progress was gradual. By 10 p.m. ET on Monday, Microsoft said mail flow was improving but search functionality remained degraded. Shortly after 3 a.m. ET on Tuesday, the company reported improvements to search as well.
As of Tuesday, Microsoft’s latest update posted to X stated that “mitigation actions are continuing to progress” and that “indications from telemetry remain positive.” The company said it was entering a period of extended monitoring to ensure a full resolution — a signal that the outage is not yet officially over.
The incident highlights the potential reach of a single authentication misconfiguration, which this outage suggests may cascade across multiple enterprise services simultaneously. Businesses and users relying on Microsoft 365 for email, collaboration, and security tools could face continued intermittent disruptions until Microsoft confirms the issue is fully resolved.
Source: TechCrunch