public void SendEmail()
        {
           //string from = "13135692346@163.com";   //发送方邮箱
            string from = txtFrom.Text.ToString() + "@163.com";
            MailMessage newEmail = new MailMessage();

            #region 发送方邮件
            newEmail.From = new MailAddress(from, from);
            #endregion

            #region 发送对象，可群发
            //newEmail.To.Add(new MailAddress("369608497@qq.com"));  //接收方邮箱一
            //newEmail.To.Add(new MailAddress("13135692346@163.com"));  //接收方邮箱二
            //newEmail.To.Add(new MailAddress("402852049@qq.com"));
            //369608497@qq.com;13135692346@163.com;402852049@qq.com
            string to = txtTo.Text.ToString();
            string[]tolist=to.Split(';');
            for (int i = 0; i < tolist.Length; i++)
            {
                newEmail.To.Add(new MailAddress(tolist[i].ToString()));
            }
            #endregion

            #region Subject
            newEmail.Subject = txtSub.Text;  //标题
            #endregion

            #region Body
            string strBody = txtContent.Text.ToString(); //html格式，也可以是普通文本格式 
            newEmail.Body = strBody;  //内容
            #endregion

            #region 上传附件
            // Attachment MsgAttach = new Attachment(this.FileUpload1.PostedFile.FileName);//可通过一个FileUpload地址获取附件地址
            //newEmail.Attachments.Add(MsgAttach);
            #endregion

            #region Deployment
            newEmail.IsBodyHtml = true;                //是否支持html
            newEmail.Priority = MailPriority.High;  //优先级
            #endregion

            //发送方服务器信息
            SmtpClient smtpClient = new SmtpClient();
            smtpClient.UseDefaultCredentials = false;
            smtpClient.Credentials = new System.Net.NetworkCredential(txtFrom.Text.ToString(), txtPwd.Text.ToString());
            smtpClient.Host = "smtp.163.com"; //主机
   

            //smtpClient.Send(newEmail);   //同步发送,程序将被阻塞

            #region 异步发送, 会进入回调函数SendCompletedCallback，来判断发送是否成功
            smtpClient.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);//回调函数
            string userState = "测试";
            smtpClient.SendAsync(newEmail, userState);
            #endregion

        }
        
        private  void SendCompletedCallback(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
        {
            if (e.Cancelled)  //邮件发送被取消
            {
                //Console.WriteLine("发送被取消!");
                //Lmsg.Text = "发送被取消!";
                Response.Write("<script>alert('发送被取消!');</script>");
            }
            if (e.Error != null)   //邮件发送失败
            {
                //Console.WriteLine("发送失败！");
                //Lmsg.Text = "发送失败!";
               
                Response.Write("<script>alert('发送失败！');</script>");
            }
            else   //发送成功
            {
                //Console.WriteLine("发送成功！");
                //Lmsg.Text = "发送成功!";
                Response.Write("<script>alert('发送成功！');</script>");
            }
        }

<system.web>
..
<trust level="Full">
..
</system.web>