Forward email using MailKit - email

Question

I am trying to email EML files via Gmail SMTP server using MailKit. I followed example provided by jstedfast to build MimeMesage and send via Gmail SMTP server. I am able to send email using both the simple authentication using (user account, user password) and using OAUTH2. I followed example how to Setting up OAuth2 for use with Google Mail and all works fine, except that it seems that I have to configure access Scopes to include "https://mail.google.com/"
var accessScopes = new[]
{
"https://mail.google.com/",
"https://www.googleapis.com/auth/gmail.send"
};
otherwise sending fails with the following error:
535: 5.7.8 Username and Password not accepted. Learn more at
5.7.8 https://support.google.com/mail/?p=BadCredentials c5sm231676iod.25 - gsmtp
I assumed that I need to configure access scope with the gmail.send only but it doesn't seem to work.
"https://www.googleapis.com/auth/gmail.send"
I don't want to configure "https://mail.google.com/" which implies full access to the gmail account. When the consent screen is presented to users, users may hesitate to accept all access scopes which seems to be required otherwise sending of mails fails.
I tried to configure some of the read only scopes instead of "https://mail.google.com/" but it doesn't seem to work.
What I am missing?
Thank you

Answer 1

The "https://mail.google.com/" scope is the only scope that works with SMTP, POP3 and/or IMAP.
All of the other scopes are only available to use with the Google REST APIs.