Microsoft is investigating a widespread service outage affecting Exchange Online and several other Microsoft 365 services, causing authentication failures, connection problems, email delays, and delivery issues for tens of thousands of users. The company first acknowledged the problem at 5:30 PM UTC, after a stream of reports on social media flagged multiple issues with Exchange Online. According to outage tracking service Downdetector, tens of thousands of Outlook and Microsoft 365 users are experiencing problems receiving emails and accessing Microsoft cloud services. Microsoft has classified the event as an incident, a designation typically reserved for critical service issues with noticeable user impact.
While Exchange Online is the most heavily affected service, Microsoft has confirmed the outage also impacts OneDrive for Business, SharePoint Online, Microsoft Teams, Microsoft Purview, and Microsoft Defender XDR. The company has not yet revealed which geographic regions are affected. In an admin center update, Microsoft stated it has isolated a common failure pattern across affected Exchange Online requests, tied to authentication and protocol connectivity. Engineers are analyzing service telemetry to identify the underlying source of impact and validate potential remediation options, while also assessing the scope and monitoring for additional affected scenarios.
In a later update at 2:29 PM EDT, Microsoft attributed the outage to core authentication configuration issues. The company said it identified problems with a core authentication configuration used by multiple internal services within the Exchange Online infrastructure. Microsoft is performing manual tests on individual servers to reset configurations and validate whether that resolves the issue. At 3:09 PM EDT, Microsoft updated the incident tracking number to MO1465074, expanding the scope to include the additional Microsoft 365 services listed above.
This is not the first time Microsoft has dealt with Exchange Online problems in recent months. In June, the company mitigated a widespread service issue affecting the mail flow pipeline for customers across North America, Asia-Pacific, and Europe. In April, Microsoft resolved Exchange Online mailbox access issues that had intermittently impacted Outlook mobile and macOS users for weeks. That same month, the company also fixed an Exchange Online outage that prevented users from accessing their mailboxes via Outlook on the web, Outlook desktop, Exchange ActiveSync, and other Exchange Online connection protocols.
The current incident is being tracked under the reference EX1464935 in the Microsoft 365 admin center, alongside the newer MO1465074 designation. Microsoft has not provided a timeline for full restoration, and the company continues to assess the scope of impact across the affected services. For US-based enterprise customers and individual users relying on Outlook and Microsoft 365, the outage underscores ongoing reliability concerns with core email and collaboration infrastructure. Microsoft has not yet disclosed whether the authentication configuration issue is related to any of the previous incidents.
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