问使用Xoauth2对Gmail smtp进行身份验证。结果用户名和密码不被接受

EN

using Google.Apis.Auth.OAuth2;
using Google.Apis.Util.Store;
using MailKit.Net.Smtp;
using MailKit.Security;
using MimeKit;


var path = @"C:\YouTube\dev\credentials.json";
var scopes = new[] { "email" };
var userName = "test2";

var credential = GoogleWebAuthorizationBroker.AuthorizeAsync(GoogleClientSecrets.FromFile(path).Secrets,
    scopes,
    userName,
    CancellationToken.None,
    new FileDataStore(Directory.GetCurrentDirectory(), true)).Result;

credential.GetAccessTokenForRequestAsync();

var message = new EmailMessage()
{
    From = "xxx@gmail.com",
    To = "xxx@gmail.com",
    MessageText = "test",
    Subject = "test"
};

try
{
    using (var client = new SmtpClient())
    {
        client.Connect("smtp.gmail.com", 465, true);
        
        var oauth2 = new SaslMechanismOAuth2 ("xxx@gmail.com", credential.Token.AccessToken);
        await client.AuthenticateAsync (oauth2, CancellationToken.None);
        
        client.Send(message.GetMessage());
        client.Disconnect(true);
    }

   
}
catch (Exception ex)
{
    int i = 1;  // throws MailKit.Security.AuthenticationException here
}


public class EmailMessage
{
    public string To { get; set; }
    public string From { get; set; }
    public string Subject { get; set; }
    public string MessageText { get; set; }

    public MimeMessage GetMessage()
    {
        var body = MessageText;
        var message = new MimeMessage();
        message.From.Add(new MailboxAddress("test", From));
        message.To.Add(new MailboxAddress("test", To));
        message.Subject = Subject;
        message.Body = new TextPart("plain") { Text = body };
        return message;
    }
}