Microsoft 365 outage: Workarounds that kept offices running during Exchange Online disruption

Microsoft 365 experienced significant service disruptions on November 12 and 13, affecting Exchange Online email access and other applications, while Teams chat and calls remained functional for many users. The outage, tracked under incidents EX1550543 and MO1550821, began in the Americas before spreading globally. Microsoft attributed the issue to unexpected server failures, ruling out an attack. Teams chats and calls worked, but calendars and scheduling were affected, while SharePoint file access remained available with external sharing problems. Microsoft extended the Exchange Online delivery window to 48 hours and advised against resending delayed emails. Businesses are encouraged to develop contingency plans, including emergency mailboxes with separate providers, independent backups, and alternative communication methods, with regular testing of these procedures.