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: 10/04/2026 18:07:00 PM –Microsoft has successfully deployed the fix across the affected environments. Users may need to restart the Teams app to ensure the updated Teams Meeting Add-in is applied. They are monitoring service health for an extended period of time, to confirm that impact has been fully resolved.

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: Monday, April 20, 2026, at 10:30 AM UTC