System.Net.Mail.SmtpException：'发送邮件失败？

Question

我有一个与我们联系的asp.net网络表单，我希望将我的info @ example的电子邮件发送到我的gmail帐户，但是出现了以下错误，请查看我的代码

SocketException: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 208.118.63.36:8889

protected void ContactUs_Click(object sender, EventArgs e)
        {
            //try
            //{
                MailMessage mm = new MailMessage("info@example.com", "mygmailaccount@gmail.com");
                mm.Subject ="Message from contact us form";
                mm.Body = "Name: " + name.Text + "<br /><br />Email: " + email.Text + "<br />" + message.InnerText;
                mm.IsBodyHtml = true;
                SmtpClient smtp = new SmtpClient();
                smtp.Host = "mail.example.com";
                smtp.EnableSsl = true;
                System.Net.NetworkCredential NetworkCred = new System.Net.NetworkCredential();
                NetworkCred.UserName = "info@example";
                NetworkCred.Password = "xxxxxxxx";
                smtp.UseDefaultCredentials = true;
                smtp.Credentials = NetworkCred;
                smtp.Port = 25;
                smtp.Send(mm);
                Session["contact"]= "contect";
                Response.Redirect("~/Default#contact");