On 20 December 2025, Microsoft Teams experienced a worldwide service disruption that left users with delayed messages, missed notifications, and intermittent presence behaviour for several hours. Microsoft's incident notes pointed to infrastructure issues; no security event was involved.
For most businesses the practical impact was modest — a frustrating morning. For some, in the middle of customer-facing work or coordinating site teams, the impact was material. The interesting question after every Teams outage is the same: did your organisation have a back-up comms channel that everyone knew to fall back to? Or did people sit and refresh?
The answer for a serious business is a documented fallback: a Slack or Signal channel, an SMS group, an email distribution list, or a specific phone tree. The key is that it's documented, known, and occasionally exercised. Not invented during the outage.