Major Microsoft 365 Outage: Authentication Issues and Service Disruptions

Microsoft has launched an investigation into a major incident in its Microsoft 365 ecosystem, which resulted in authentication problems, delayed email delivery, and the unavailability of key services. The incident, identified as EX1464935, was recorded on August 31 at approximately 17:30 UTC, when users began massively reporting issues on social media.

Initially, the problems affected Exchange Online, but Microsoft later confirmed that the outage had spread to other services, including OneDrive for Business, SharePoint Online, Microsoft Teams, Microsoft Purview, and Microsoft Defender XDR. According to Downdetector, thousands of users encountered difficulties accessing cloud services and receiving emails via Outlook.

Symptoms of the outage in Exchange Online included delays or errors when sending and receiving emails, issues with searching content in mailboxes, authentication errors when accessing services, and difficulties in administration and message delivery. Microsoft noted that it had identified a common failure pattern related to authentication and protocol connectivity.

On August 31 at approximately 14:29 EDT, the company stated that the cause of the outage was problems with the authentication configuration used by several internal services within the Exchange Online infrastructure. Specialists initiated manual testing at the server level to reset configurations and verify troubleshooting capabilities. By September 1 at around 03:43 EDT, Microsoft reported restored connectivity to mailboxes, though search functionality was still being restored.