Microsoft 365 Outage Hits Outlook, Teams & Copilot As 48-Hour Email Safeguard Begins

Microsoft's latest outage triggered nearly 140,000 Outlook problem reports across 74 countries and territories, disrupting Outlook, Teams and Copilot. Surprisingly, the disruption wasn't caused by unusually high traffic, but by unavailable servers overwhelming the remaining infrastructure.
 

TL;DR

• Microsoft's November 12 outage disrupted Outlook, Teams, Copilot and other Microsoft 365 services.
• Downdetector recorded reports across 74 countries and territories, although the total number of affected users remains unknown.
• Microsoft traced the increased infrastructure load to unexpectedly unavailable servers.
• Recovery efforts are progressing, with some services improving, but full restoration remains unconfirmed.

Microsoft 365 Outage Reaches 74 Countries As Outlook Reports Surge

The disruption began on November 12, with Microsoft initially acknowledging Exchange Online mailbox connection problems across the Americas. However, what appeared to be a regional Outlook issue quickly expanded into a wider Microsoft 365 outage.

According to Downdetector figures cited in reports, Outlook problem reports peaked globally around 18:00 GMT on Thursday, exceeding normal reporting levels by more than 2,000 times.

The figures represent user-submitted reports, not Microsoft's confirmed number of affected customers, which remains undisclosed.

As reported earlier, the disruption affected business and consumer services, with Microsoft warning that users in any region could experience connectivity problems.
 

Microsoft Traces Outlook Connectivity Errors To Unexpected Server Failures

Microsoft initially identified unusually high infrastructure load across multiple regions, which appeared to explain the widespread connectivity errors.

The twist? Microsoft later determined that the overload wasn't driven by a traffic surge.

Instead, several servers had unexpectedly become unavailable, forcing the remaining infrastructure to handle additional demand and causing connection failures.

Microsoft investigated a server-health processing component after discovering that certain machines were failing automated health checks. Engineers tested alternative checks, restarted affected servers, paused deployments and redistributed connection traffic across its worldwide infrastructure.

However, some restored servers became unresponsive again after receiving traffic.

The company subsequently identified an overwhelmed core process and began testing configuration changes, rebuilding affected servers and restricting certain traffic to stabilize operations.

Microsoft has not established a definitive root cause or found evidence linking the disruption to malicious cyber activity.
 

 

Outlook, Teams And Copilot Disruptions Affect Microsoft 365 Services

The outage affected several Microsoft services differently, with Outlook users experiencing problems accessing mailboxes, sending messages and receiving emails.

Microsoft Teams users faced disruptions involving Exchange-dependent functionality, including calendar scheduling and meeting invitations. However, core Teams messaging and online meetings remained largely operational.

Microsoft 365 Copilot also experienced connectivity problems involving workplace information, including emails, calendars and files. The disruption highlights the dependence on interconnected services underlying Microsoft's expanding Copilot automation capabilities.

Other affected products included SharePoint Online integrations, Microsoft Defender XDR, Purview, Planner, To Do and administrative services.

Microsoft tracked the Exchange Online disruption under incident EX1550543 and the broader Microsoft 365 issue under MO1550821.
 

 

Microsoft Begins Restoring Outlook Access But Full Recovery Remains Unconfirmed

By November 13, Microsoft's incident updates indicated progress after an authentication and routing configuration patch helped improve server stability.

Recovery efforts showed encouraging results in parts of Asia-Pacific, with mailbox connectivity improving and delayed email processing gradually resuming.

Microsoft also extended email timeouts to 48 hours, aiming to preserve delayed messages while its infrastructure recovered.

However, intermittent failures remain possible as engineers gradually restore traffic and apply recovery measures across additional regions.

Microsoft has not announced complete service restoration or published its final root-cause findings.