Microsoft has said a recent deployment that contained a "broken connection to an internal storage service" was the likely cause of an outage that left many users unable to access or use various Microsoft 365 apps for several hours.  

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The service issues, which started on the evening of Wednesday July 20 and continued into Thursday morning, slowed down or prevented access to several Microsoft services, including Microsoft Teams, Exchange Server, Microsoft 365 admin center, Yammer, Microsoft Word and other Office applications. The issue also prevented autopatching within Microsoft Managed Desktop and other services.

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Microsoft said most service availability was up and running as of this morning (July 21), although some services are still suffering from issues, meaning users may struggle to access some Microsoft 365 services for the time being. 

"We've determined that a recent deployment contained a broken connection to an internal storage service, which has resulted in impact," the company Tweeted.

We've determined that a recent deployment contained a broken connection to an internal storage service, which has resulted in impact. We're working to direct traffic to a healthy service to mitigate impact. Additional information can be found in the admin center under TM402718.

- Microsoft 365 Status (@MSFT365Status) July 21, 2022

It added: "Service availability has mostly recovered with only a few service features still requiring attention. We'll continue to monitor the service while the remaining actions are completed."

A further update at lunchtime (BST) suggested that services were almost fully returned to normal, but that the situation is still being monitored: "We believe that the majority of services have recovered. We're continuing to monitor the issue to ensure there is no residual impact.".

By the afternoon (BST) the Microsoft 365 Service health status page indicated that there was no longer a problem.  

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According to Microsoft, the full list of affected services included:

• Microsoft Teams (Access, chat, and meetings) 
• Exchange Online (Delays sending mail) 
• Microsoft 365 Admin center (Inability to access) 
• Microsoft Word within multiple services (Inability to load)
• Microsoft Forms (Inability to use via Teams) 
• Microsoft Graph API (Any service relying on this API may be affected) 
• Office Online (Microsoft Word access issues) 
• SharePoint Online (Microsoft Word access issues) 
• Project Online (Inability to access) 
• PowerPlatform and PowerAutomate (Inability to create an environment with a database) 
• Autopatches within Microsoft Managed Desktop 
• Yammer (Impact to Yammer experiments) 
• Windows 365 (Unable to provision Cloud PCs)  

Microsoft has updated its Microsoft 365 Service health status "Current status: Our telemetry indicates that service availability continues to be above 99% across the majority of regions. Some users in the UK region may experience residual impact with certain features in Microsoft Teams. We're continuing to monitor the service to ensure full recovery and apply targeted mitigations for any residual impact," it said. 

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