Microsoft Graph REST API not able to write mail - azure

Question

I'm using graph rest api for writing a draft mail.
First, I called the authorize method with the https://graph.microsoft.com/.default scope:
https://login.microsoftonline.com/common/oauth2/v2.0/authorize?client_id=MY_CLIENT_ID&response_type=code&redirect_uri=https://login.microsoftonline.com/common/oauth2/nativeclient&response_mode=query&scope=https://graph.microsoft.com/.default
With the obtained code, I called the token method with the same scope:
https://login.microsoftonline.com/common/oauth2/v2.0/token
With this token, I am able to get messages without any issues, but when I try to create a draft by calling: https://graph.microsoft.com/v1.0/me/messages/ I get the following error:
{
"error": {
"code": "ErrorAccessDenied",
"message": "Access is denied. Check credentials and try again.",
"innerError": {
"request-id": "7fafbb5a-ab6d-4dbc-bb73-69d58b00f7ac",
"date": "2019-11-26T20:48:24"
}
}
}
As stated in the documentation (https://learn.microsoft.com/en-us/graph/api/user-post-messages?view=graph-rest-1.0&tabs=http) I have set the Mail.ReadWrite permission in my registered Azure app and granted admin consent. Am I missing something?

Answer 1

I checked Graph logs and that call to Microsoft Graph did not have the Mail.ReadWrite permission. Can you try adding that permission to the scope query param in your implicit auth flow call instead of .default? (If you need multiple permissions you can list them all in the scope param separated by spaces)