A widespread Microsoft outage disrupted Outlook email and other Microsoft 365 services Thursday, with problems continuing into Friday morning.
Nearly 130,000 Outlook problem reports were recorded on Downdetector around Thursday’s peak, as users struggled to open inboxes and send or receive messages.
Microsoft reported progress restoring service Friday but said intermittent problems remained. The company said it had no evidence of malicious activity.
A widespread Microsoft outage that began Thursday continued disrupting email and workplace applications Friday morning, leaving users unable to reliably access Outlook and portions of the company’s Microsoft 365 platform.
The disruption affected customers across multiple regions and extended beyond personal and business email. Companies and some government operations experienced problems, with users in Asia also reporting difficulties as their Friday workday began.
In a service update issued shortly after 6 a.m. Eastern time Friday, Microsoft said recovery work had progressed across portions of its Asia Pacific infrastructure. Mailbox access and delayed email processing were improving, although some users continued experiencing intermittent problems.
The company said it was expanding those recovery efforts to other affected regions and adding capacity to improve stability. It also extended its email timeout window to 48 hours to help protect delayed messages while delivery backlogs cleared.
What went wrong
Microsoft’s investigation identified a process responsible for establishing secure connections that became overwhelmed, causing affected servers to stop processing requests. With servers unavailable, additional work shifted to the remaining infrastructure.
Restoring service proved difficult. Some servers initially recovered but became unresponsive again when traffic returned. Microsoft’s response included restarting infrastructure, adjusting traffic routing and testing configuration changes. The company also began reversing a recent network configuration change that coincided with the disruption’s onset. A final explanation of the underlying cause remained pending.
Why several applications were affected
Exchange Online, Microsoft’s cloud email service, supports features used throughout its workplace software. Consequently, an email infrastructure failure can also disrupt calendars, scheduling and other connected functions.
Microsoft said Outlook users could experience problems across web, desktop and mobile connections. Copilot users could also have trouble loading chats, receiving responses or accessing workplace information.
The impact varied by feature. Most core Teams calling, meeting and messaging functions remained available, while calendar and scheduling tools could fail. Direct access to files stored in SharePoint Online also remained functional, although some connected features were affected.
For consumers, the most visible symptoms included inboxes that would not load, connection errors and delayed messages. The nearly 130,000 Outlook reports recorded by Downdetector reflected user submissions rather than a complete count of affected customers.
Microsoft said Friday morning that it had no evidence of malicious activity associated with the incident and would publish a detailed report after mitigation was complete. Customers can follow developments through the Microsoft service status page, while workplace administrators can review incident MO1550821 in the Microsoft 365 admin center.