Investigation
The issue was detected at 4:00 PM CET on June 16, 2025, after users reported that signatures were no longer automatically inserted in Outlook Desktop Classic. The engineering team began the investigation on June 17, 2025, at 7:04 AM CET.
Upon reviewing the pipeline configurations and deployment logs, the team quickly identified the discrepancy between the updated project name and the unchanged pipeline template as the root cause. The static build step had not executed, leading to a missing artifact in the final deployment.
Mitigation
At 7:23 AM CET on June 17, 2025, the engineering team initiated work on a fix by updating the pipeline template file to match the new project name and restoring the custom build step.
Deployment of the fix to production began at 8:14 AM CET, starting with West Europe (Production 0). The fix was successfully deployed to Production 0 by 8:29 AM CET and was then rolled out to the remaining production clusters.
Resolution
By 8:29 AM CET on June 17, 2025, the fix had been successfully deployed to West Europe (Production 0) and was being propagated to all other production clusters. The static assets required for automatic signature insertion were restored, and the functionality in Outlook Desktop Classic returned to normal.
Post-Incident Actions
Impact and Scope
The incident affected the automatic email signature insertion feature in Outlook Desktop Classic for tenants served by the following clusters:
The issue impacted a subset of users depending on the Outlook Desktop Classic experience across these clusters
We sincerely apologize for the disruption caused by this issue. Maintaining a reliable and seamless experience is our highest priority, and we are taking immediate steps to prevent such oversights in the future. We remain committed to delivering high-quality and dependable service.