💡 Our Technical Review in summary
Summary
Users in SharePoint Online may have experienced a failure in receiving email notifications when mentioned (@mentioned) in list comments between January 8, 2026, and January 24, 2026. The issue was caused by a service update intended to remove an unrelated feature, which accidentally introduced a regression in the SharePoint Online notification system.
Impact
Impact was limited to specific users mentioned in SharePoint list comments. These users did not receive the standard automated email alerts, which may have resulted in missed communications or delays in responding to list-based tasks and discussions.
Status
Service Restored. Microsoft has successfully reverted the offending service change across the affected environment. Following an extended period of monitoring and telemetry validation, the service has been confirmed as fully remediated. IT Admins do not need to take any further action.
Microsoft Official Issue Details
User Impact
Users that were mentioned in list comments in SharePoint Online may have not received email notifications.
Status: serviceRestored
Service: SharePoint Online
Classification: advisory
Origin: microsoft
Updates
- 2026-01-24 01:27
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notificationsUser impact: Users that were mentioned in list comments in SharePoint Online may have not received email notifications.
Final status: Our reversion of the offending change has completed its saturation process throughout the affected environment, and we’ve confirmed through an extended period of monitoring the service health telemetry that impact has been remediated.
Scope of impact: Impact was specific to some users that were mentioned in list comments in SharePoint Online.
Start time: Thursday, January 8, 2026, at 12:24 PM UTC
End time: Saturday, January 24, 2026, at 1:07 AM UTC
Root cause: A recent service change to remove a separate feature introduced a regression within SharePoint Online email notifications, which resulted in impact.
Next steps:
– We’re continuing to analyze how the service change was partially applied to understand why the potential for impact wasn’t caught during the update testing and validation phase. These actions will help us to clarify what actions we can take to ensure similar impact doesn’t occur in future and to continue our ongoing mission to improve the resilience of our service for all SharePoint Online users.This is the final update for the event.
- 2026-01-23 16:52
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notificationsUser impact: Users that are mentioned in list comments in SharePoint Online may not receive email notifications.
Current status: We’re continuing to monitor progress of our fix to reverse the offending change, where it’s saturated across 90 percent of the affected infrastructure. We estimate that this saturation will complete by our next communications update, after which we’ll perform final testing with a subset of affected users to validate remediation.
Scope of impact: Impact is specific to some users that are mentioned in list comments in SharePoint Online.
Start time: Thursday, January 8, 2026, at 12:24 PM UTC
Root cause: A recent service change to remove a separate feature introduced a regression within SharePoint Online email notifications, resulting in impact.
Next update by: Saturday, January 24, 2026, at 3:00 AM UTC
- 2026-01-22 18:00
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notificationsUser impact: Users that are mentioned in list comments in SharePoint Online may not receive email notifications.
Current status: We’re continuing to monitor progress of the fix to reverse the offending change and will provide a resolution timeline once available.
Scope of impact: Impact is specific to some users that are mentioned in list comments in SharePoint Online.
Start time: Thursday, January 8, 2026, at 12:24 PM UTC
Root cause: A recent service change to remove a separate feature is causing impact.
Next update by: Friday, January 23, 2026, at 6:30 PM UTC
- 2026-01-21 18:49
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notificationsUser impact: Users that are mentioned in list comments in SharePoint Online may not receive email notifications.
Current status: We’re continuing to reverse the offending change and will provide a timeline for the completion of this reversal as one becomes available.
Scope of impact: Impact is specific to some users that are mentioned in list comments in SharePoint Online.
Start time: Thursday, January 8, 2026, at 12:24 PM UTC
Root cause: A recent service change to remove a separate feature is causing impact.
Next update by: Thursday, January 22, 2026, at 7:00 PM UTC
- 2026-01-21 17:22
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notificationsUser impact: Users that are mentioned in list comments in SharePoint Online may not receive email notifications.
Current status: We’ve identified a recent service change to remove a separate feature is causing impact. While we investigate the reason the change caused impact, we’re reversing the offending change to remediate the impact.
Scope of impact: Impact is specific to some users that are mentioned in list comments in SharePoint Online.
Start time: Thursday, January 8, 2026, at 12:24 PM UTC
Root cause: A recent service change to remove a separate feature is causing impact.
Next update by: Wednesday, January 21, 2026, at 7:30 PM UTC
- 2026-01-21 15:24
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notificationsUser impact: Users that are mentioned in list comments in SharePoint Online may not receive email notifications.
Current status: We’ve identified a potential update that may be causing impact to occur. We’re analyzing the update code path to confirm the update is the root cause of impact.
Scope of impact: Impact is specific some users that are mentioned in list comments in SharePoint Online.
Next update by: Wednesday, January 21, 2026, at 5:30 PM UTC
- 2026-01-21 13:20
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notifications.User impact: Users that are mentioned in list comments in SharePoint Online may not receive email notifications.
Current status: We’re reviewing any recent changes to the service that may be causing impact to occur.
Scope of impact: Impact is specific some users that are mentioned in list comments in SharePoint Online.
Next update by: Wednesday, January 21, 2026, at 3:30 PM UTC
- 2026-01-21 11:18
Title: Some users that are mentioned in list comments in SharePoint Online may not receive email notificationsUser impact: Users that are mentioned in list comments in SharePoint Online may not receive email notifications.
Current status: We’re reviewing service monitoring telemetry to isolate the root cause and determine our next troubleshooting steps.
Scope of impact: Impact is specific some users that are mentioned in list comments in SharePoint Online.
Next update by: Wednesday, January 21, 2026, at 1:30 PM UTC
