private void btntest_Click(object sender, EventArgs e)
        {
            MailMessage message = new MailMessage();

            // if (FileUpload1.PostedFile.FileName != "")
            // {
            //  Attachment att = new Attachment("d://test.txt");//发送附件的内容
            //    message.Attachments.Add(att);
            // }

            message.From = new MailAddress("xxx@126.com", "kevin", Encoding.UTF8);
            message.To.Add("xxx@126.com"); //收件人邮箱地址可以是多个以实现群发 
            message.Subject = "test2";
            message.Body = "test2";
            //message.Attachments.Add(objMailAttachment);
            message.IsBodyHtml = false; //是否为html格式 
            message.Priority = MailPriority.High; //发送邮件的优先等级 

            SmtpClient sc = new SmtpClient();
            sc.Host = "smtp.126.com"; //指定发送邮件的服务器地址或IP 
            sc.Port = 25; //指定发送邮件端口 
            sc.Credentials = new System.Net.NetworkCredential("knwolf@126.com", "kingwolf0923"); //指定登录服务器的用户名和密码 

            try
            {
                sc.Send(message); //发送邮件 
            }
            catch (Exception ex)
            {
                throw ex;
            }
            MessageBox.Show("发送成功！");
        }