Microsoft Reports Exchange Online Disruption Slowing External Email Delivery

Microsoft confirmed a new service incident affecting its Exchange Online platform, identified as incident EX1467029, that is delaying the transmission of email messages originating from or destined for external domains. The company first publicly acknowledged the problem on September 4, 2026, classifying it as a service‑degradation issue rather than a complete outage.

Exchange Online is a core component of Microsoft 365, providing cloud‑based email, calendar, and contacts for millions of organizations worldwide. Because the service handles the majority of inbound and outbound corporate mail, any slowdown in external message flow can impede routine communications, disrupt collaboration, and potentially affect time‑sensitive business processes.

According to Microsoft’s service‑health updates, the disruption is not uniform across all tenants; some customers are experiencing noticeable latency while others see only minor slowdowns. The root cause has not been disclosed, but the incident has been logged in Microsoft’s internal tracking system, and engineers are actively working to isolate the fault.

Microsoft advises customers to monitor the Service Health dashboard for real‑time status changes and to follow any remediation steps posted there. Organizations that rely heavily on external email are encouraged to use alternative channels—such as instant messaging or phone calls—if urgent communication is required while the issue persists.

The episode underscores the reliance of modern enterprises on cloud‑based email infrastructure and highlights the importance of contingency planning. Microsoft has pledged to provide further updates as the investigation progresses and to restore normal delivery speeds as quickly as possible.