Microsoft Exchange Online outage causes email failures, auth issues

Microsoft experienced a significant service outage impacting Exchange Online and several other Microsoft 365 services due to core authentication configuration failures within Exchange Online infrastructure. The incident caused authentication errors, email delivery delays and failures, incomplete mailbox search results, and intermittent mailbox operation failures. Microsoft tracked the incident under internal codes EX1464935 and MO1465074 and provided ongoing updates as they implemented targeted mitigations. The outage lasted approximately three days, with progressive recovery and final resolution confirmed by Microsoft. The outage also affected additional services including Microsoft Teams, Microsoft Graph, Microsoft Purview, OneDrive for Business, SharePoint Online, Microsoft 365 Admin Center, Microsoft 365 Copilot, Universal Print, and Microsoft Defender XDR. Microsoft continues to monitor telemetry to ensure service stability.

The outage caused widespread authentication failures and service disruptions for Exchange Online users, resulting in delays and failures in sending and receiving emails, failures in mailbox search functionality, and difficulties accessing Exchange administration features. Additional Microsoft 365 services experienced degraded availability and functionality during the incident. The outage was classified as critical due to its broad impact on core productivity services. Users experienced inability to download email attachments and sign in to Outlook on the web during the incident. The outage affected tens of thousands of users globally, though no specific regional targeting was identified.

Microsoft has fully mitigated the outage and restored all affected services. No further user action is required. Microsoft continues to monitor service telemetry to ensure ongoing stability. Organizations should follow Microsoft’s official communications for any updates but no specific remediation steps are necessary from customers as this was a service-side issue managed by Microsoft.