how to configure SmtpClient server ip address

var smtp = new System.Net.Mail.SmtpClient();
        {
            smtp.Host = "127.0.0.0";
            smtp.Port = 25;
            smtp.EnableSsl = true;
            smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
            smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
            smtp.Timeout = 20000;
        }
        try
        {
            smtp.Send(fromAddress, toAddress, subject, body);
        }
        catch(Exception ex) {
            Response.Write(ex);
        }