Microsoft is investigating a major outage of the Microsoft Exchange Online service that is preventing users in North and South America from accessing their mailboxes.
See also: High severity vulnerability in Microsoft Exchange
The ongoing incident, tracked as ID EX1151485 in the admin center, is affecting all methods of signing in to the email service. Microsoft initially acknowledged the issue, saying it was affecting a portion of its infrastructure located in North America. Users have reported being unable to access their mailboxes through any sign-in method, including Outlook desktop, web, or mobile clients.
In response, the company has launched an investigation to identify the source of the Microsoft Exchange Online outage. The company has begun evaluating service telemetry to look for potential system anomalies that could be contributing to the widespread access failures. System administrators have been directed to the Administration Center for the most up-to-date information about the incident.
See also: Microsoft Outlook faces outage
As the investigation continued, Microsoft engineering teams began implementing changes to mitigate the impact. The company began implementing optimizations to the affected mailbox infrastructure in parallel with their diagnostic efforts. These changes are being rolled out gradually to stabilize the environment and restore service without causing additional issues.
Microsoft said it is closely monitoring the health of the service to confirm that optimizations are being applied across the affected infrastructure as expected, ensuring a controlled recovery process. Optimization efforts have led to some improvements to the service, with access gradually being restored for some users.
As fixes continue to be deployed, Microsoft expects further recovery across the affected infrastructure. In analyzing the incident, the company also found that the issue was not isolated to North America. A subset of users in South America were also identified as being affected by the same mailbox access issue, expanding the scope of the incident.
See also: Microsoft Outlook: Blocks other file types to prevent phishing
Microsoft advises all affected customers to continue to report EX1151485 in the admin center for the latest updates on service restoration.
