US & EU: Intermittent Microsoft Graph Errors Creating Calendars & Events

Microsoft has confirmed that the Graph API errors affecting calendar and event creation were caused by a backend issue related to the deprecation of Skype. This introduced a conflict in the code used to retrieve calendar information, particularly for shared calendars.

A fix has now been fully deployed across their infrastructure, and internal testing by Microsoft has validated that the issue was resolved as of July 8, 2025.

We have observed no further errors on our side since the fix was applied. Microsoft has also indicated that they are reviewing the impacted code paths to improve testing and prevent similar issues in the future.

This incident is now considered resolved. Thank you for your patience throughout this issue.

The issue remains ongoing, with no change in behavior observed. We have submitted a Severity A support ticket with Microsoft and are currently awaiting their response regarding the Graph API errors impacting a subset of calendar and event creation requests.

Our engineering team continues to monitor closely and will provide updates as soon as new information becomes available.

We are seeing `ErrorInternalServerError` API errors from a small number of Microsoft grants when attempting to create new events or new calendars in the Nylas API.

We have confirmed that these errors are coming from Microsoft Graph API email servers and have reached out to Microsoft to address this issue.

Additionally, if you retry a failed API call to create a new calendar, a different error 409 `ErrorFolderExists` may be returned. This error is also from Microsoft Graph API.

This does not appear to be affecting any on-premise Exchange (EWS) grants or other email providers.