Allow upload mime format email via Microsoft Graph REST to arbitrary folder, not just Drafts

I could upload mime format email with "POST: /users/{id|userPrincipalName}/messages/" , "Content-Type: text/plain; charset=utf-8" headers and base64 encoded mime message in body, but failed to upload with "POST /users/{id | userPrincipalName}/mailFolders/{id}/messages" although I could upload in JSON format.