private void AuthenticateImapGoogleOAuth2(Imap4Client imap)
        {
            var auth = new GoogleOAuth2Authorization();
            var granted_access = auth.RequestAccessToken(Account.RefreshToken);
            if (granted_access == null) return;
            _log.Info("IMAP SSL connecting to {0}", Account.EMail);
            imap.ConnectSsl(Account.Server, Account.Port);

            _log.Info("IMAP connecting OK {0}", Account.EMail);

            _log.Info("IMAP logging to {0} via OAuth 2.0", Account.EMail);
            imap.LoginOAuth2(Account.Account, granted_access.AccessToken);
            _log.Info("IMAP logged to {0} via OAuth 2.0", Account.EMail);
        }
        private void AuthenticateImapGoogleOAuth2(Imap4Client imap)
        {
            var auth = new GoogleOAuth2Authorization(_log);
            var granted_access = auth.RequestAccessToken(Account.RefreshToken);
            if (granted_access == null) 
                throw new DotNetOpenAuth.Messaging.ProtocolException("Access denied");
            _log.Info("IMAP SSL connecting to {0}", Account.EMail);
            imap.ConnectSsl(Account.Server, Account.Port);

            _log.Info("IMAP connecting OK {0}", Account.EMail);

            _log.Info("IMAP logging to {0} via OAuth 2.0", Account.EMail);
            imap.LoginOAuth2(Account.Account, granted_access.AccessToken);
            _log.Info("IMAP logged to {0} via OAuth 2.0", Account.EMail);
        }