Abstract:
On November 13, Microsoft stated that the large-scale service failure that lasted for nearly two days was gradually being repaired. The availability and mail delivery performance of Outlook mailboxes and other Microsoft 365 services had improved, but some users may still experience intermittent connection problems. The outage began on Thursday afternoon and affected businesses, government agencies and other organizations around the world.
The fault involves Outlook, Teams, Copilot, and many Microsoft services such as Word, Excel, PowerPoint, SharePoint and OneDrive. Network failure monitoring website Downdetector recorded nearly 130,000 related failure reports on Thursday afternoon. Local governments in Baltimore County, Jacksonville, and Austin in the United States were affected, and some government departments and the National Health Service (NHS) in the United Kingdom also experienced communication outages. Air India reported blocked customer service communications, and OpenAI and Anthropic also experienced issues connecting to Microsoft 365 services.
Microsoft said the failure mainly involved the Exchange Online infrastructure that supports Outlook email and calendar services. The workload of some servers increased abnormally, and some servers unexpectedly stopped providing services during the automatic detection process, causing user connections to be blocked. The company is improving service by restoring servers, redistributing traffic and deploying software fixes, and is working through a backlog of delayed mail.
At present, Microsoft has not determined the root technical cause of the failure, but said it has found no signs that the incident was caused by malicious activity or a cyber attack. The company is still continuing to restore the remaining affected systems and has not yet announced a specific time for all services to return to normal.
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