Status Page

O365 - Email/Outlook

2025-10-21	Status	Description
03:19 PM		Service Health Incident EX1176994, Status Service Degradation Details Title: Some users may be unable to access their Exchange Online email using Outlook for Mac User impact: Users may be unable to access their Exchange Online email using Outlook for Mac. More info: Some users’ Mac devices may be quarantined, which is prohibiting impacted users from accessing their email in Outlook for Mac. Impact is specific to the latest build, 16.102.1018.1. Current status: We've confirmed the latest build version contains a code issue which is causing the Exchange ActiveSync policy to block the Outlook for Mac client, resulting in the impact. We're reverting the latest build to resolve the issue. Scope of impact: This issue impacts 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 Root cause: The latest build release contains a code issue which is causing the Exchange ActiveSync policy to block the Outlook for Mac client, resulting in the impact. Next update by: Tuesday, October 21, 2025, at 10:30 PM UTC
10:01 AM		Service Health Incident EX1173600, Status Service Restored Details Title: Some users may have the new Outlook client open in their web browser instead of the Desktop client User impact: Users had the new Outlook client open in their web browser instead of the Desktop client. More info: As a workaround, users were able to use the classic Outlook to access their Exchange Online mailbox. Final status: Our fix deployment is complete, and we’ve confirmed from service telemetry that this issue is resolved. Affected users may need to restart Outlook, potentially more than one time, to pick up the fix. Scope of impact: Your organization was affected by this event, and some users attempting to open the new Outlook client were impacted. Start time: Tuesday, October 14, 2025, at 3:00 AM UTC End time: Friday, October 17, 2025, at 4:00 PM UTC Root cause: A code issue contained in a recent service update was causing a race condition and resulting in the impact. Next steps: - We’re continuing our investigation to determine exactly how the offending code bug was introduced to better detect and prevent issues like this from occurring in the future. This is the final update for the event.

2025-10-17	Status	Description
01:56 PM		Service Health Incident EX1173828, Status Service Degradation Details Title: Users may be unexpectedly signed out from Outlook on the web when accessing shared mailboxes User impact: Users may be unexpectedly signed out from Outlook on the web when accessing shared mailboxes. Current status: We’re continuing our assessment of the errors observed when users attempt to access shared mailboxes in Outlook on the web, as we work to isolate the cause of this issue and determine an appropriate remediation action. Scope of impact: This issue can potentially affect any user when accessing shared mailboxes from Outlook on the web. Next update by: Friday, October 17, 2025, at 10:30 PM UTC
09:11 AM		Service Health Incident EX1173600, Status Service Degradation Details Title: Some users have the new Outlook client open in their web browser instead of the Desktop client User impact: Users have the new Outlook client open in their web browser instead of the Desktop client. More info: As a workaround, users are able to use the classic Outlook to access their Exchange Online mailbox. Current status: We've identified that a code bug contained in a recent service update is causing a race condition and resulting in the impact. We've developed a fix to address the code issue which we're preparing to deploy to the affected environment. We'll aim to provide a timeline for the fix to deploy by our next scheduled communications update. Scope of impact: Your organization is affected by this event, and some users attempting to open the new Outlook client are impacted. Root cause: A code issue contained in a recent service update is causing a race condition and resulting in the impact. Next update by: Monday, October 20, 2025, at 9:00 PM UTC