465端口发送邮件

2017年买的阿里云服务器 客服说暂停25端口邮件的发送  只能改为465，这样就遇到了用web.mail 引用发送邮件
只能吧版本降到4.0


public static void SendEmail(string subject, string body, string mailTo, List<string> mailCC, List<string> attachmentUrls)
        {
            MailMessage mmsg = new MailMessage();
            //验证   
            mmsg.Subject = subject;// "zhuti1";//邮件主题

            mmsg.BodyFormat = MailFormat.Html;
            mmsg.Body = body;// "wqerwerwerwer";//邮件正文
            mmsg.BodyEncoding = Encoding.UTF8;//正文编码

            mmsg.Priority = MailPriority.High;//优先级

            mmsg.From = "Service01@yz365.com";//发件者邮箱地址
            mmsg.To = mailTo;//收件人收箱地址
            StringBuilder mailCCString = new StringBuilder();

            foreach (var cc in mailCC)
            {
                mailCCString.Append(cc + ";");
            }
            mmsg.Cc = mailCCString.ToString();

            foreach (var attachmentUrl in attachmentUrls)
            {
                MailAttachment oAttch = new MailAttachment(attachmentUrl, MailEncoding.Base64);

                mmsg.Attachments.Add(oAttch);

            }

            mmsg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate", "1");
            //登陆名   
            mmsg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendusername", "Ser@163.com");
            //登陆密码   
            mmsg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/sendpassword", "登陆密码  ");

            mmsg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpserverport", 465);//端口  
            mmsg.Fields.Add("http://schemas.microsoft.com/cdo/configuration/smtpusessl", "true");
            System.Web.Mail.SmtpMail.SmtpServer = "smtp.163.com";    //企业账号用smtp.exmail.qq.com  

            SmtpMail.Send(mmsg);
        }

 string topic = "测试邮件topic";
            List<string> attachmentUrls = new List<string> { "E:\附件.txt" };
            string body = "一封含附件的测试邮件";// "<h1>一封含附件的测试邮件</h1>";


            ClassLibrary1.MailSenderHelper.SendEmail(topic, body, "123456@qq.com", new List<string> { "7898@qq.com" }, attachmentUrls);
            Console.WriteLine("发送成功");
            Console.ReadLine();