Graph api create custodian 500 unexpected error

Question

I’m encountering another issue with 500 internal server error code with lack of detail.

 

What fails

• POST /security/cases/ediscoveryCases/{caseId}/custodians
• Request body is exactly per the documentation: { "email": "<smtp>" }
• Response: 500 InternalServerError — {"error":{"code":"InternalServerError","message":"An unexpected error occurred."}}
• It fails on every retry (we retry with backoff) and is not intermittent.

 

500 Internal Server Error on POST request for https://graph.microsoft.com/v1.0/security/cases/ediscoveryCases/smapel_request_id/custodians: "{"error":{"code":"InternalServerError","message":"An unexpected error occurred.","innerError":{"date":"2026-09-04T19:35:37","request-id":":)","client-request-id":"5f6b6357-0dc0-47ee-b24b-37ef4d52d148"}}}"

Could you check why this happens. I'm not even getting details