Microsoft 365 Outage Tops 12 Hours, Fix Failing
Original: Microsoft Outlook/365 still down after 12 hours
Why This Matters
M365 serves hundreds of millions of business users; a 12-hour outage has real economic cost.
Microsoft 365 and Outlook remained down for over 12 hours on Nov 13, 2026, as fixes failed to take hold. Exchange Online and broader M365 services were affected globally under incident IDs EX1550543 and MO1550821.
What started as reports of Exchange Online mailbox access issues in the Americas quickly spread worldwide. Microsoft confirmed that a portion of its infrastructure was experiencing elevated load across multiple regions — not from a traffic spike, but because an unspecified number of servers went unexpectedly offline, straining the remaining capacity.
Microsoft's response escalated through the night: the company paused all deployments, restarted affected servers, and began redistributing traffic across its global infrastructure. None of it worked as intended. In their latest update at 3:13 AM, Microsoft admitted the applied changes were "not taking as expected" and said they were "identifying alternate workstreams" to address sustained traffic management imbalances.
The incident ID EX1550543 covers Exchange Online; MO1550821 tracks the broader Microsoft 365 impact. The outage's X post thread racked up 18 million views on the initial alert alone, underscoring the scale of disruption.