异步操作已被取消

我正在尝试发送一封电子邮件（代码取自Microsoft文档），但操作被取消并且邮件没有收到邮件。帮助解决问题。

static bool mailSent = false;
    private static void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
    {

        String token = (string)e.UserState;

        if (e.Cancelled)
        {
            Console.WriteLine("[{0}] Send canceled.", token);
        }
        if (e.Error != null)
        {
            Console.WriteLine("[{0}] {1}", token, e.Error.ToString());
        }
        else
        {
            Console.WriteLine("Message sent.");
        }
        mailSent = true;
    }


    public static void SendMessage()
    {           
        SmtpClient client = new SmtpClient();
        client.Host = "smtp.gmail.com";
        client.Port = 465;
        client.UseDefaultCredentials = false;
        client.Credentials = new NetworkCredential(mailFrom, password);

        MailAddress from = new MailAddress(mailFrom,"saturn",System.Text.Encoding.UTF8);

        MailAddress to = new MailAddress(mailTo);

        MailMessage message = new MailMessage(from, to);
        message.Body = "This is a test e-mail message sent by an application. ";

        message.BodyEncoding = System.Text.Encoding.UTF8;
        message.Subject = "test message 1";
        message.SubjectEncoding = System.Text.Encoding.UTF8;

        client.SendCompleted += new
        SendCompletedEventHandler(SendCompletedCallback);

        string userState = "test message1";
        client.SendAsync(message, userState);            

        if (mailSent == false)
        {
            client.SendAsyncCancel();
        }

        message.Dispose();
    }