服務器不支持安全連接

Server does not support secure connections.
服務器不支持安全連接

下面是原碼：

private static void sendMail(string name, string email)
    {
        string smtpServer = "ksmail01.服务器
        int smtpPort = 25;//端口
        string userAccount = "******** ";//用户名
        string userPassword = "***************";//密码
        string userName = "系統管理員";//发件人名称
        string EmailAddress = "Missyatem@发件邮箱
        string strto = email;//目的邮箱
        string strSubject = "dd";//主题
        string strBody = "ss";
         client = new SmtpClient(smtpServer, smtpPort);
        client.EnableSsl = true;
        client.UseDefaultCredentials = true;
        client.Credentials = new (userAccount, userPassword);
        client.DeliveryMethod =

        MailAddress fromEmal = new MailAddress(EmailAddress, userName);
        MailAddress toEmail = new MailAddress(strto);
         message = new MailMessage(fromEmal, toEmail);
        message.Subject = strSubject;
        message.Body = strBody;
        message.BodyEncoding = System.Text.Encoding.UTF8;
        message.IsBodyHtml = true;
        client.Send(message);
    }

請大路過的大俠賜教 ，