/// <summary>
        /// 
        /// </summary>
        /// <param name="from">发件邮箱账号</param>
        /// <param name="pwd">发件邮箱账号密码</param>
        /// <param name="to">收件人邮箱</param>
        /// <param name="title">主题</param>
        /// <param name="content">内容</param>
        /// <param name="attachFileName">附件</param>
        /// <param name="pihao">我自己的一个用来重新命名附件的参数</param>
        /// <returns></returns>
        public static string SendEmail(string from, string pwd, string to, string title, string content, string attachFileName,string pihao)
        {
            string[] strs = from.Split('@');
            string[] strs2 = strs[1].Split('.');
             
            //发送
            SmtpClient client = new SmtpClient(string.Format("smtp.{0}.com", strs2[0]));   //设置邮件协议
            client.UseDefaultCredentials = false;//这一句得写前面
            client.EnableSsl = true;
            switch (strs2[0])
            {
                case"163":
                    case"126":
                    case"qq":
                    case"sina":
                    client.Port = 25;
                    break;
                case"Gmail":
                    client.Port = 587;
                    break;
                default:
                    client.Port = 25;
                    break;
            }
           // client.Port = 25;
            client.DeliveryMethod = SmtpDeliveryMethod.Network; //通过网络发送到Smtp服务器
            client.Credentials = new NetworkCredential(strs[0].ToString(), pwd); //通过用户名和密码 认证
        
            
            string newFileName = "";
            //因为之前附件名是guid命名的，所以怕因为这个会被当成垃圾邮件，所以重新命名附件
            if (File.Exists(attachFileName))
            {
                FileInfo fi = new FileInfo(attachFileName);
                string dire = Path.GetDirectoryName(attachFileName);
                string ex = fi.Extension;
                newFileName = Path.Combine(dire,"报告单"+pihao+ex);
                fi.CopyTo(newFileName,true);
            }
            MailMessage mmsg = new MailMessage();
            try
            {
                mmsg = new MailMessage(new MailAddress(from), new MailAddress(to)); //发件人和收件人的邮箱地址
                mmsg.Subject = title;      //邮件主题
                mmsg.SubjectEncoding = Encoding.UTF8;   //主题编码
                mmsg.Body =content;         //邮件正文
                mmsg.BodyEncoding = Encoding.UTF8;      //正文编码
                mmsg.IsBodyHtml = true;    //设置为HTML格式           
                mmsg.Priority = MailPriority.High;   //优先级

                if (newFileName != "")
                {
                    mmsg.Attachments.Add(new Attachment(newFileName));//增加附件
                }

                client.Send(mmsg);
               
                return "邮件发送成功！OK!";

            }

            catch (System.Net.Mail.SmtpException ex)
            {

                return "邮件发送失败，请稍后重试！Sending message to server failed,please try again latter";
                // MessageBox.Show(ex.Message);
            }
            finally
            {
               
                mmsg.Dispose();
                //需要释放mmsg后再delete
                File.Delete(newFileName);
            }
        }