Microsoft 365 Alert – Service Degradation – Microsoft Teams – Some users may experience delays when accessing the calendar using the classic Outlook desktop app – RESOLVED

Announcements Arpan Das

30/06/2025 08:50:00 AM

NHSmail Reference: INC46566502

Microsoft Reference: TM1104705

Issue Status: RESOLVED

Issue Description: Users may experience delays when accessing the calendar using the classic Outlook desktop app.

More info: Impact is specific to users that have disabled the local address book accessing their calendar using the classic Outlook desktop app with the Teams Meeting add-in (TMA) installed.

While they are working to remediate impact, affected users can access their calendar using the following calendar options:

– New Outlook desktop app
– Outlook on the web
– Microsoft Teams desktop app
– Microsoft Teams web app
– Microsoft Teams mobile app

Final Update: 11/07/2025 08:45:00 AM – Microsoft have confirmed that the fix has been fully deployed throughout the affected environment. Impacted users may need to ensure they’ve updated to the latest version of Microsoft Teams and restarted their classic Outlook desktop app to see full remediation.

Scope of impact: Impact is specific to a low number of users utilizing OutlookWin32 and TMA version: 1.25.14602, who are located on or served through the affected infrastructure.

Root cause: A recent service update introduced a change to TMA functionality which contains a code error, resulting in impact.

Next steps: Microsoft are reviewing their update testing and validation methods to better identify code issues such as this prior to deployment to prevent similar impact in the future.