C#发送邮件为何出现下列错误？？？？

C# code

       protected void SendMail()        {            try            {                //create the mail message                MailMessage myMail = new MailMessage();                //set the addresses                myMail.From = new MailAddress("service@gn.com.cn");                myMail.To.Add( "593234579@qq.com");                //set the content                myMail.Subject = "有短信未发送" + DateTime.Now.ToLongTimeString();                myMail.Body = "有" + MyClass.Dlookup("select count(*) from sms where dirty = 1 and datediff(day,updatetime,getdate())>1") + "条短信未发出";                //send the message                SmtpClient smtp = new SmtpClient("mail.gn.com.cn");                smtp.Credentials = new NetworkCredential("service@gn.com.cn", "51012345");                smtp.Send(myMail);            }            catch (Exception e)            {                lbMessage.Text = e.Message;            }        }

为何出现了以上错误？？？


[解决办法]
应当是你的邮件服务器配置问题
直接 给你一个类吧

C# code

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Net.Mail;using System.Configuration;    public class SendMail    {        string emailname = ConfigurationManager.AppSettings["emailname"].ToString();        string emailpwd = ConfigurationManager.AppSettings["emailpwd"].ToString();        string host = ConfigurationManager.AppSettings["emailhost"].ToString();        public void SendMailTo(string from, string body)        {            try            {                //mail服务器设置                SmtpClient mailserver = new SmtpClient();                mailserver.Host = host;                mailserver.Credentials = new System.Net.NetworkCredential(emailname, emailpwd);                mailserver.Timeout = 5000;                mailserver.EnableSsl = true;                //mail邮件设置                MailMessage mail = new MailMessage();                MailAddress mfrom = new MailAddress(emailname);                mail.From = mfrom;                mail.To.Add(from);                mail.Subject = "";                mail.SubjectEncoding = System.Text.Encoding.GetEncoding("GB2312");                mail.BodyEncoding = System.Text.Encoding.GetEncoding("GB2312");                mail.IsBodyHtml = true;                mail.Body = "";                mailserver.Send(mail);            }            catch (Exception ex)            {                throw ex;            }        }    }