New Delhi, Nov. 13 -- Microsoft Corp. is struggling to restore access to its flagship software half a day after an outage began, leaving users unable to access email and chat services in one of the tech giant's most severe disruptions in recent memory.

Users across the world on Friday reported problems with Outlook, Teams and the Copilot artificial intelligence tool, after the services were unavailable for many during the previous day in the US. Microsoft's products are among the most widely used software among business, government and educational institutions.

The outage, which attracted about 200,000 reports of user issues on Downdetector, ranks among the company's most significant. Previous disruptions have rarely lasted more than se...