Microsoft 365 Alert – Service Degradation – Exchange Online – Some users may be unable to use Microsoft Outlook Classic while the Microsoft Teams Meeting Add-in is enabled- ONGOING

17/03/2026 09:14:00 AM

NHSmail Reference: INC46775188

Microsoft Reference: EX1254044

Issue Status: ONGOING

Issue Description: Some users may be unable to use Microsoft Outlook Classic while the Microsoft Teams Meeting Add-in is enabled.

More info: If Teams Meeting Add-in is disabled then Outlook Classic functions as normal.

As a workaround, users can also perform an Online Repair of Office or update Outlook to the latest version to resolve the issue.

Current Update: 07/04/2026 08:43:00 AM –Microsoft are continuing to deploy the fix across the affected environments. While some environments may have already received the fix, they expect the rollout to complete by Thursday, April 9, 2026. Once the fix reaches your environment, users may need to restart the Teams app to ensure the updated Teams Meeting Add-in is applied. They are closely monitoring deployment progress throughout the rollout.

Scope of impact: Users attempting to use Microsoft Outlook Classic while the Microsoft Teams Meeting Add-in and previous Outlook build version is enabled may be impacted.

Root cause: A previous Outlook build version that is enabled is causing impact to occur.

Next update by: Friday, April 10, 2026, at 10:30 AM UTC