Exchange Online Service Outage Causes Email Delays and 'Server Busy' Errors
Microsoft status page indicates ongoing disruption affecting external domain communication
Key Takeaways
- Exchange Online service outage reported starting 2026-09-04 causing email delays and 'Server busy' errors.
- Impact is global, affecting communication with external domains; no evidence of exploitation or data theft reported.
- Microsoft is actively working on a resolution, but no patch or fix timeline has been provided.
- The incident is classified as a service availability issue rather than a security breach.
Quick answers
- What happened?
- Microsoft Exchange Online users worldwide are experiencing email delivery delays and 'Server busy' errors when communicating with external domains. The outage, reported starting on 2026-09-04, appears to be a service availability issue with no evidence of active exploitation, ransomware, or data theft. Microsoft is actively working on a resolution, but no patch or fix timeline has been provided.
- Which products are affected?
- Exchange Online
- What should defenders do?
- Monitor Microsoft's official status page for updates. Users experiencing delays should wait for Microsoft to resolve the issue. No immediate patch is available as this is an infrastructure issue.
A widespread outage affecting Microsoft Exchange Online began being reported on 2026-09-04. Users are experiencing email delays and 'Server busy' errors when sending or receiving messages to and from external domains. Microsoft acknowledged the issue and is working to resolve it, stating that the problem impacts global connectivity to the cloud service. As of the latest updates, the root cause has not been publicly disclosed, and no timeline for a complete fix has been issued. The company has not reported any evidence of active exploitation, ransomware, or data theft associated with the outage, classifying it as an infrastructure availability incident. Affected parties include Microsoft Exchange Online subscribers and their external correspondents. Microsoft's status page is being updated to reflect progress on the resolution.
Security Details
No evidence of active exploitation, ransomware, or data theft reported. Issue appears to be a service availability problem.
Affected products
Exchange Online
Mitigation
Monitor Microsoft's official status page for updates. Users experiencing delays should wait for Microsoft to resolve the issue. No immediate patch is available as this is an infrastructure issue.
Sources
BleepingComputer
Exchange Online outage causes email delays, 'Server busy' errors
Sep 4, 2026 · 12:22
Original link
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