Microsoft Corp.’s Outlook email service went down for users on Thursday, the latest disruption to a product businesses rely on for daily communication.
The company said the service was initially reported as affected across the U.S. and the Americas before the problem widened to include “any region.” Microsoft did not identify a root cause. In a post on X aimed at users who could not reach its admin center, the company said parts of its infrastructure were carrying “elevated load” and that it was “redistributing connection traffic across our broader worldwide infrastructure to help balance the load.”
In a later status update, Microsoft said the elevated load was not driven by an overall increase in traffic but by “a large number of servers being unexpectedly unavailable,” which shifted work onto the remaining infrastructure. The company said it had paused all deployments and configuration changes while it reviewed recent changes for any correlation with the failure, and that it was “aggressively pursuing all pathways” to reduce the impact.
The disruption reached beyond email. A Microsoft 365 advisory, MO1550821, listed Exchange Online, Teams, SharePoint Online, Microsoft 365 Copilot and Microsoft Defender XDR among the services that could be affected, while the mail failure itself was tracked as incident EX1550543. A separate Teams incident in North America, TM1550488, was reported at 10:40 a.m. ET and resolved around noon.
| Time (ET, Nov. 12) | Time (JST, Nov. 13) | Event |
|---|---|---|
| 10:40 a.m. | 12:40 a.m. | Microsoft reports Teams problems in North America |
| About noon | About 2 a.m. | Teams issue resolved as outage reports begin to climb |
| 1:07 p.m. | 3:07 a.m. | Microsoft says the impact may reach Microsoft 365 users in “any region” |
| 1:09 p.m. | 3:09 a.m. | Outlook outage reports reach 128,874 |
| 1:48 p.m. | 3:48 a.m. | Microsoft says it has begun redistributing connection traffic worldwide |
| About 2 p.m. | About 4 a.m. | Reports exceed 130,000; service still degraded |
Times are U.S. Eastern; Japan Standard Time is 14 hours ahead.
Outage-tracking site Downdetector logged more than 100,000 reports of Outlook problems during the incident. Microsoft’s status page, where customers normally check for service updates, also appeared to be unreachable.
The company said it was posting updates in its admin center, which was not accessible at the time. As of 2:47 p.m. ET, Microsoft listed the issue as a service degradation and said its next update was due by 10 p.m. UTC.
Thursday’s failure was the second Exchange Online disruption this week. On Nov. 9, a separate incident blocked Outlook on the web for users in Europe, the Middle East and Africa for about 4.5 hours, with Microsoft citing “unexpected connection terminations” in part of its Exchange Online infrastructure, according to incident records compiled by the tracking service IsDown. In September, a multi-day outage hit Microsoft 365, the online productivity suite that includes Outlook; Microsoft attributed that failure to a “core authentication configuration” problem that blocked users from signing in.
| Date | Scope | Duration | Microsoft’s stated cause |
|—|—|—|
| Aug. 31-Sept. 3 | Worldwide | About four days | A misconfigured “core authentication configuration” |
| Nov. 9 | Europe, Middle East and Africa | About 4.5 hours | “Unexpected connection terminations” within part of Exchange Online |
| Nov. 12 | Americas, then “any region” | Ongoing as of 2:47 p.m. ET | Many servers “unexpectedly unavailable,” shifting load to the remaining systems |
Microsoft 365 is a core part of Microsoft’s business: the productivity and business processes segment that houses it generated $37.8 billion in the quarter ended June 30, about 42% of the company’s $90.0 billion in revenue, with commercial Microsoft 365 cloud revenue up 14% from a year earlier.