SmtpClient smtpServer = new SmtpClient("smtp.163.com");

                smtpServer.Port = ;

                smtpServer.Credentials = new System.Net.NetworkCredential("feiyang", "");

                smtpServer.EnableSsl = true;

                MailMessage mail = new MailMessage();

                mail.From = new MailAddress("feiyang@163.com");//和上面的对应

                mail.To.Add("1234@qq.com");

                mail.Subject = "会员注册信息";//标题

                mail.SubjectEncoding = Encoding.UTF8;

                mail.Body = mailBoby;

                mail.Priority = System.Net.Mail.MailPriority.High;//邮件优先级

                mail.IsBodyHtml = true;

                smtpServer.SendAsync(mail, "userToken");//异步发送第二个参数时一个用户定义对象，此对象将被传递给完成异步操作时所调用的方法,参数默认即可
               // smtpServer.Send(mail);//同步发送

 System.Net.Mail.SmtpClient smtp = new System.Net.Mail.SmtpClient();

                    smtp.Host = "smtp.163.com";

                    smtp.Credentials  =new System.Net.NetworkCredential("feiyang","");

                    smtp.SendAsync("feiyanghenan@163.com", "1234@qq.com", "平台用户关联验证", "验证码：" + new Random().Next(, ).ToString(), "userToken");