error in smtp sending mail reg

protected void Page_Load(object sender, EventArgs e)
   {
       if (!IsPostBack)
       { }
   }
   protected void Button1_Click(object sender, EventArgs e)
   {
       Response.Write(SendMail("info@letrouters.com", "info@letrouters.com", "info@letrouters.com", "Test Mail", "Test Mail Body"));
   }
    public string SendMail(string toList, string from, string ccList, string subject, string body)
   {
       MailMessage message = new MailMessage();
       SmtpClient smtpClient = new SmtpClient();
       string msg = string.Empty;
       try
       {
           MailAddress fromAddress = new MailAddress(from);
           message.From = fromAddress;
           message.To.Add(toList);
           if (ccList != null && ccList != string.Empty)
               message.CC.Add(ccList);
           message.Subject = subject;
           message.IsBodyHtml = true;
           message.Body = body;
           smtpClient.Host = "mail.letrouters.com";
           smtpClient.Port = 25;
           smtpClient.UseDefaultCredentials = true;
           smtpClient.Credentials = new System.Net.NetworkCredential("info@letrouters.com", "XXXXX");

           smtpClient.Send(message);
           msg = "Successful";
       }
       catch (Exception ex)
       {
           Response.Write(ex.Message);
       }

      return msg;
   }