Microsoft 365 Outage Disrupts Outlook, Copilot and More Worldwide

Microsoft is experiencing a widespread outage affecting several of its major online services, including Outlook, Teams, Microsoft 365 Copilot, SharePoint and parts of its wider cloud platform.

For many users, the disruption is more than an inability to access webmail. Outlook desktop and mobile users have also reported problems connecting to their accounts, loading mailboxes, sending or receiving messages, and synchronising data. Copilot has also been unavailable or unresponsive for some users.

As a Hotmail user since January 2004, I have never experienced anything like this.

The incident is being tracked by Microsoft under two separate advisories: EX1550543, concerning Exchange Online mailbox access, and MO1550821, covering the broader Microsoft 365 disruption.

What has been affected?

The outage appears to be centred on Exchange Online, the cloud infrastructure that powers Microsoft-hosted email. Microsoft has warned that users may experience problems with:

• Outlook on the web
• Outlook desktop and mobile applications
• Sending and receiving email
• Calendar and contact data
• Microsoft Teams features that depend on Exchange Online
• Microsoft 365 Copilot and Copilot Chat
• SharePoint Online
• Microsoft Graph requests involving Exchange data
• Some Microsoft Defender, Intune, Planner, and To Do functionality

Not every Microsoft service is necessarily affected. Features that do not depend on Exchange Online may continue to work, which explains why some users can access certain Microsoft applications while others fail completely.

What does Microsoft say has happened?

Microsoft’s initial updates suggested that a large number of servers had unexpectedly become unavailable. The remaining servers were then placed under increased load, creating further connectivity and capacity problems across multiple regions.

The company later said that affected servers were failing automated health checks. These checks are intended to determine whether servers are healthy enough to handle customer traffic. Microsoft believes that a specific component involved in processing those checks may be contributing to the problem.

Engineers have attempted several recovery measures, including restarting affected servers, shifting traffic to alternative routes, applying configuration changes and rebuilding some infrastructure using an earlier configuration.

Recovery has been uneven. Microsoft reported that some servers returned to service, but others became unresponsive again after receiving traffic. As a result, users may see services work intermittently or recover gradually rather than returning to normal all at once.

Microsoft has also said it has found no evidence to date that the incident was caused by malicious activity.

This is a solid reminder of how dependent modern software has become

This outage highlights the growing dependence of everyday software on cloud infrastructure.

• A locally installed application may still depend on remote services for:
• Account authentication
• Licence verification
• Cloud-based settings
• Synchronisation
• Artificial intelligence features
• File storage
• Updates
• Security checks
• Access to email, calendars or contacts

That arrangement offers clear advantages. Users can access their data from multiple devices, organisations can manage accounts centrally, and applications can receive frequent updates without traditional installation processes.

However, it also creates a single point of dependency. When a major provider experiences an outage, the effects can spread well beyond the company’s own websites. Email, collaboration tools, business applications and even unrelated software that relies on Microsoft authentication can all be affected.

Is this being fixed?

Microsoft has been applying recovery measures and has reported early signs of stabilisation in some regions. However, the incident remains more complicated than a simple server restart. Some infrastructure returned to service only to become unstable again under normal traffic.

Users should therefore expect a gradual and potentially inconsistent recovery. One person may regain access while another continues to experience errors, depending on their region, account, connection method and the specific Microsoft services they use.

The latest information is available through Microsoft’s public service health page. Organisations with Microsoft 365 administration access can also check the detailed advisories in the Microsoft 365 admin centre.

What should users do?

There is not much that individual users can do to repair the underlying problem, but a few practical steps may help:

• Avoid repeatedly changing passwords or reinstalling Office applications.
• Save any locally available work.
• Try Outlook on the web, desktop, or mobile at different times.
• Use alternative communication methods if email and Teams are unavailable.
• Avoid assuming that an activation warning means a subscription has actually expired.
• Check Microsoft’s service health updates before changing account or licence settings.
• If an application is working offline, avoid signing out unless necessary.

For businesses, this is also a reminder of the importance of having contingency plans for email and collaboration outages. Alternative communication channels, offline access, independent backups and documented recovery procedures can make a significant difference when a cloud provider experiences a major incident.