Microsoft has recently verified an issue with Exchange Online, identified as incident EX1467029, which is causing delays in email exchanges with external domains. This incident has been classified as a service degradation affecting one of the top-used business email platforms globally.
Timeline of the Outage
The disruption was first acknowledged by Microsoft on September 4, 2026. The issue commenced around 3:49 PM GMT+5:30 and had several updates throughout the afternoon, with reports logged at 4:06 PM, 4:33 PM, and 5:56 PM.
Users have experienced intermittent ‘Server busy’ messages when attempting to send emails to recipients outside their organizations. This symptom indicates processing delays on the backend rather than a total halt in mail flow. Microsoft has deemed this a significant incident due to its broad impact on users.
Contributing Factors and Ongoing Investigation
Microsoft’s advisories reveal that anti-spam systems may be exacerbating the problem for some users by slowing down legitimate emails. The engineering teams are currently analyzing service telemetry and behavior to understand the root cause and develop an effective solution.
Despite ongoing efforts, Microsoft has not yet provided a timeline for full resolution. The company continues to explore mitigation strategies to address the underlying issues.
Recent Similar Incidents
This incident follows a series of disruptions to Exchange Online, including a significant outage identified as EX1464935 that started on August 31, 2026. The previous incident involved authentication issues, delayed deliveries, and was attributed to a fault in a core authentication component.
The recurrence of such problems raises concerns about the reliability of Microsoft’s cloud email services, which are vital for enterprises worldwide.
Organizations dependent on Exchange Online for time-sensitive communications, such as customer support or security alerts, are advised to monitor real-time updates via the Microsoft 365 admin center’s Service Health dashboard.
Recommendations and Security Concerns
Security teams should remain vigilant, as prolonged email delays might result in missed threat notifications or delayed multi-factor authentication emails. Backlogs could also increase the risk of phishing attacks exploiting user confusion during these periods.
Until Microsoft can provide a permanent fix, administrators should check for undelivered emails and avoid resending messages to prevent further queue strain. Continued updates will be provided as Microsoft releases more information on the situation.
Stay informed about the latest developments on this issue to ensure your organization’s communication remains secure and efficient.
