Send email by using MailKit with Gmail

// Send email by using MailKit with Gmail

using (var emailClient = new SmtpClient())
{
    // https://console.developers.google.com
    var secrets = new ClientSecrets
    {
        ClientId = "",
        ClientSecret = ""
    };

    // Generating a refresh token - https://www.youtube.com/watch?v=hfWe1gPCnzc
    var token = new TokenResponse { RefreshToken = "YourRefreshToken" };
    var googleCredentials = new UserCredential(new GoogleAuthorizationCodeFlow(
        new GoogleAuthorizationCodeFlow.Initializer
        {
            ClientSecrets = secrets
        }), SmtpUsername, token);

    emailClient.Connect("smtp.gmail.com", 587, SecureSocketOptions.StartTls);

    await googleCredentials.GetAccessTokenForRequestAsync();
    var oauth2 = new SaslMechanismOAuth2(SmtpUsername, googleCredentials.Token.AccessToken);
    emailClient.Authenticate(oauth2);

    await emailClient.SendAsync(message); // MimeMessage
    emailClient.Disconnect(true);
}