User impact: Users may have been unable to access their Exchange Online email using Outlook for Mac.

More info: Some users’ Mac devices may have been quarantined, which prohibited impacted users from accessing their email in Outlook for Mac.

Impact is specific to the latest build, 16.102.1018.1.

Final status: We’ve confirmed with reporting users that the issue is now resolved. If you are still experiencing impact, close, then reopen Outlook and wait ten seconds. If you receive an error message that says, “This account has been blocked on this device by your administrator,” please repeat the steps above until you no longer receive the error message.

Scope of impact: This issue impacted users on the latest version (16.102.1018.1) of the Outlook for Mac client.

Start time: Monday, October 20, 2025, at 4:00 PM UTC

End time: Tuesday, October 21, 2025, at 8:30 PM UTC

Root cause: The latest build release contained a code issue which caused the Exchange ActiveSync policy to block the Outlook for Mac client, resulting in the impact.

Next steps:
– To help prevent similar impact in the future, we’re further reviewing our testing and validation processes prior to deployment.

We’ll provide a preliminary Post-Incident Report within two business days and a final Post-Incident Report within five business days.