def _cbAuthenticated(self, loginInfo):
        """
        Save the state resulting from a successful cred login and mark this
        connection as authenticated.
        """
        result = SMTP._cbAnonymousAuthentication(self, loginInfo)
        self.authenticated = True
        return result

        Save the state resulting from a successful cred login and mark this
        connection as authenticated.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/mail/smtp.py