Outage in Microsoft 365

Users may be unable to open the new Outlook desktop client app on Windows devices

Resolved Minor
August 19, 2025 - Started about 13 hours ago - Lasted about 9 hours

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Outage Details

Title: Users may be unable to open the new Outlook desktop client app on Windows devices User impact: Users may be unable to open the new Outlook desktop client app on Windows devices. More info: As a workaround, affected users may be able to use the Outlook classic desktop client. Current status: We're analyzing support provided information to determine our next troubleshooting steps. Scope of impact: Your organization is affected by this event, and users attempting to open the new Outlook desktop client on Windows devices may be impacted. Next update by: Tuesday, August 19, 2025, at 5:30 PM UTC
Components affected
Exchange Online
Latest Updates ( sorted recent to last )
about 6 hours ago - at 08/19/2025 05:15PM

Title: Users may be unable to open the new Outlook desktop client app on Windows devices

User impact: Users may be unable to open the new Outlook desktop client app on Windows devices.

More info: As a workaround, affected users may be able to use the Outlook classic desktop client.

Current status: We’ve isolated a recent build update that we’ve confirmed introduced this issue. We’ve initiated the process of reverting the service back to the last known healthy build to remediate the impact as we continue our investigation to determine the underlying change that led to the impact.

Scope of impact: Your organization is affected by this event, and users attempting to open the new Outlook desktop client on Windows devices may be impacted.

Start time: Monday, August 18, 2025, at 10:00 PM UTC

Root cause: A recent deployment intended to optimize services dependent in the affected scenario caused crashes to occur on these services, leading to the impact.

Next update by: Tuesday, August 19, 2025, at 7:30 PM UTC

about 12 hours ago - at 08/19/2025 10:34AM

Title: Users may be unable to open the new Outlook desktop client app on Windows devices

User impact: Users may be unable to open the new Outlook desktop client app on Windows devices.

More info: As a workaround, affected users may be able to use the Outlook classic desktop client.

Current status: We're analyzing support provided information to determine our next troubleshooting steps.

Scope of impact: Your organization is affected by this event, and users attempting to open the new Outlook desktop client on Windows devices may be impacted.

Next update by: Tuesday, August 19, 2025, at 5:30 PM UTC

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