问MailMessage System.Net.Mail.SmtpException，尝试通过C#表单发送电子邮件时出错

EN

using System.Net;
using System.Web;
using System.Net.Mail;

private void BtnEmail_Click(object sender, EventArgs e)
        {


            try
            {
                string to = "myEmail@gmail.com";
                string from = "myEmail@gmail.com";
                string subject = "Test email";
                string body = @"This is a test email";


                MailMessage mail = new MailMessage(from, to, subject, body);
                SmtpClient client = new SmtpClient("smtp.gmail.com");
                client.Credentials = new NetworkCredential ("myEmail@gmail.com", "myPassword");
                client.Port = 587;
                client.EnableSsl = true;
                client.Send(mail);
                MessageBox.Show("Mail Sent", "Success", MessageBoxButtons.OK);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message + "\n\n" + ex.GetType().ToString() + "\n\n" + ex.StackTrace, "Exception");
            }
        }