Exchange Online: The Microsoft 365 email service behind Outlook outages

Microsoft's Exchange Online, the cloud-hosted messaging platform behind Outlook, experienced widespread outages affecting email, calendars, and contacts for numerous organizations using Microsoft 365. The service stores mailboxes that Outlook apps access, meaning a single back-end fault can disrupt all Outlook versions and other tools like Teams simultaneously. Microsoft hosts the platform, with customers managing users while Microsoft handles infrastructure and updates. Exchange Online includes filtering, compliance tools, and supports various connection protocols. Its centralized design means shared system failures, such as authentication or networking issues, can impact many users at once despite redundant database copies.