mail.send is not accepting HTML/ CSS code

[Digital_WorkerB]

I have copied the (HTML) source code from a received email just to have the template/format of that email, and this is the error message that I am receiveing when running the API:

Internal : Unexpected error Error during Web API HTTP Request
HTTP Status Code: 400
HTTP Response Content: {
  "error": {
    "code": "BadRequest",
    "message": "Unable to read JSON request payload. Please ensure Content-Type header is set and payload is of valid JSON format.",
    "innerError": {
      "date": "2020-12-02T17:01:05",
      "request-id": "3ab50fc1-0c13-4536-96db-bf6b9b7a736d",
      "client-request-id": "3ab50fc1-0c13-4536-96db-bf6b9b7a736d"
    }
  }
}

I have tested basic commands using HTML such as making text bold and line breaks which work, but anything more complex and I will receive an error.

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Disclaimer: This content was auto-posted from Stackoverflow. The original Stackoverflow question is here Stackoverflow Post, posted by DomF.