The Microsoft Graph API offers to create messages in the user mailbox (https://docs.microsoft.com/en-us/graph/api/user-post-messages?view=graph-rest-1.0&tabs=http). Unfortunately, the permission requested is only Mail.ReadWrite. We feel that it is way too large. We would like Microsoft Graph to support Mail.Write permission only.
Example of the same message creation feature on Google side which require the 'gmail.insert' permission only (https://developers.google.com/gmail/api/reference/rest/v1/users.messages/insert)