问题 I have been trying to implement email functionality in a legacy app using the Legacy Mail API to add OAuth support after getting a token through the Device Code Flow starting with the Microsoft Sample Project. Along that route I have added SMTP.Send and many other API permissions to find the missing piece. (Including { "User.Read", "User.ReadBasic.All", "SMTP.Send", "offline_access", "Mail.Send" } in fear of missing one) I have been testing with the MailKit library to build a proof of concept