The problems began on Thursday, when Microsoft first flagged trouble with Exchange Online mailboxes in the Americas shortly before 1 p.m. GMT. The outage has likely hit around 430 million users who use Microsoft 365 apps, which includes Outlook and Teams. According to BBC, over 90% of Fortune 500 companies use Copilot. Microsoft's global outage disrupted Outlook, Teams, Copilot and other services, affecting businesses, airlines and government operations.