User impact: Users may have been unable to access the default add-ins in Outlook.

More info: This issue impacted both the Outlook desktop client and Outlook on the web. Some affected users found that the “My Templates” icon was missing from the Outlook ribbon, and others were unable to find templates in the AppData Microsoft Templates location, even though templates were known to exist and were still being used by non-impacted users. Some users also reported that the Viva Insights add-in was impacted by this event.

Final status: We’ve identified that a recent Exchange Web Services (EWS) deprecation update and an Exchange Online authentication change prevented users from accessing default add-ins in Outlook. To remediate this issue, we rolled back both offending changes and verified through service monitoring that this action successfully resolved the impact. Admins that have disabled EWS may continue to experience this issue and we recommend that admins re-enable EWS at this time. For additional guidance on managing Exchange Web Services, please refer to the following:
learn.microsoft.com/en-us/exchange/client-developer/exchange-web-services/how-to-control-access-to-ews-in-exchange

Scope of impact: Some users attempting to access or use the default add-ins within Outlook may have been impacted.

Start time: Thursday, March 12, 2026, at 10:04 PM UTC

End time: Friday, March 27, 2026, at 1:40 AM UTC

Root cause: A recent EWS deprecation update and an Exchange Online authentication change prevented users from accessing default add-ins in Outlook.

Next steps:
– We’re reviewing how the impacting changes prevented users from accessing default add-ins so we can avoid similar issues in the future, as EWS is slated to be deprecated by October 2026.

This is the final update for the event.