Microsoft Exchange Online Service Down – Millions of Users Unable to Access Their Mailbox

Microsoft Exchange Online experienced a major global outage on July 10, 2025, preventing millions of users from accessing their mailboxes across multiple platforms. The incident, designated as EX1112414, began at 10:20 PM UTC on July 9 and continued affecting users worldwide for more than 11 hours.

The outage has affected users across multiple regions, including North America, Europe, Australia, and parts of Asia. Major cities reported significant disruptions, including New York, Washington, Dallas, London, Delhi, Berlin, and Sydney.

Users have been unable to access their Exchange Online mailboxes through various connection methods, including:

• Outlook on the web
• Outlook desktop client
• Outlook mobile applications
• Exchange ActiveSync (EAS)
• Messaging API (MAPI)
• Representational State Transfer (REST) API

According to DownDetector, over 2,100 users reported issues with Outlook services by 9:30 AM ET on July 10, with 62% experiencing login problems, 33% facing server connection errors, and 5% unable to send emails.

Microsoft’s initial investigation identified that a portion of the mailbox infrastructure was not performing as efficiently as expected. The company later determined that a recent service update was unintentionally preventing access for a subset of users, resulting in intermittent service unavailability.

Further analysis suggested the issue was related to a malfunctioning authentication component that was impairing users’ ability to log in and access email services.

Microsoft’s Response and Updates

Microsoft acknowledged the issue through its Service Health Dashboard and began deploying corrective measures. The company provided several status updates throughout the incident:

• Initial Response (July 9, 10:20 PM UTC): Microsoft confirmed users were unable to access their mailboxes and began investigating the issue.
• Early Investigation (July 10, 3:30 AM UTC): The company identified underperforming mailbox infrastructure and suspected authentication component issues.
• Fix Deployment (July 10, 7:00 AM UTC): Microsoft announced it had determined the cause of the issue and started deployment of a fix, noting that the deployment was “progressing quicker than anticipated”.
• Configuration Changes (July 10, 9:34 PM GMT+5:30): Microsoft validated that configuration changes were effective in resolving the impact in the targeted infrastructure and began deploying the expedited configuration change globally.

The company stated it was following safe change management processes to ensure stability during the fix deployment.

As of the latest update provided at 9:34 PM GMT+5:30 on July 10, Microsoft has validated that the configuration change has been effective in resolving the impact in targeted infrastructure and has started deploying the expedited configuration change broadly worldwide to all affected infrastructure.

The company is working to provide an estimated remediation timeline and continues to monitor the deployment process to ensure no additional issues arise.

During the outage, affected users received various error messages, including “Something went wrong,” “invalid licenses,” and authentication failures. Many users reported being unable to access critical business communications and client documents.

While the primary Exchange Online services were disrupted, other Microsoft 365 services, including Teams, Skype, and OneDrive, appeared to remain functional, suggesting the issue was specific to Exchange Online infrastructure.

This incident follows a pattern of Microsoft 365 service disruptions in 2025, including a major outage in June 2025 that affected Teams and Exchange Online due to routing configuration issues.

The current outage represents one of the more significant Exchange Online disruptions, with its extended duration and global scope affecting millions of users worldwide.

Microsoft has emphasized that this is an ongoing investigation, and users should monitor the official Service Health Dashboard for the most current updates on restoration efforts.

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