VS 2008 Email Verification

preusing System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net;
using System.Net.Sockets;
namespace EmailValidation
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public static string SmtpServer;
        private enum SMTPResponse : int
        {
            CONNECT_SUCCESS = 220,
            GENERIC_SUCCESS = 250,
            DATA_SUCCESS = 354,
            QUIT_SUCCESS = 221
        }
        public bool VerifyEmail()
        {
            string address = textBox2.Text.Trim();
            string[] host = (address.Split('@'));
            string hostname = host[1];
            IPHostEntry IPhst = Dns.GetHostEntry(hostname);
            IPEndPoint endPt = new IPEndPoint(IPhst.AddressList[0], 80);//25 //21 //Port?
            Socket s = new Socket(endPt.AddressFamily,
                         SocketType.Stream, ProtocolType.Tcp);
            s.Connect(endPt);
            //Attempting to connect
            if (!Check_Response(s, SMTPResponse.CONNECT_SUCCESS))
            {
                s.Close();
                return false;
            }
            //HELLO server
            Senddata(s, string.Format("HELLO {0}\r\n", Dns.GetHostName()));
            if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
            {
                s.Close();
                return false;
            }
            //Identify yourself
            //Servers may resolve your domain and check whether
            //you are listed in BlackLists etc.
            Senddata(s, string.Format("MAIL From: {0}\r\n",
                 "[my_email]"));
            if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
            {
                s.Close();
                return false;
            }
            //Attempt Delivery (I can use VRFY, but most
            //SMTP servers only disable it for security reasons)
            Senddata(s, address);
            if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))
            {
                s.Close();
                return false;
            }
            return (true);
        }
        private static void Senddata(Socket s, string msg)
        {
            byte[] _msg = Encoding.ASCII.GetBytes(msg);
            s.Send(_msg, 0, _msg.Length, SocketFlags.None);
        }
        private static bool Check_Response(Socket s, SMTPResponse response_expected)
        {
            string sResponse;
            int response;
            byte[] bytes = new byte[1024];
            while (s.Available == 0)
            {
                System.Threading.Thread.Sleep(100);
            }
            s.Receive(bytes, 0, s.Available, SocketFlags.None);
            sResponse = Encoding.ASCII.GetString(bytes);
            response = Convert.ToInt32(sResponse.Substring(0, 3));
            if (response != (int)response_expected)
                return false;
            return true;
        }
        private void button1_Click(object sender, EventArgs e)
        {
                       bool Result = VerifyEmail();
            if (Result == true)
            {
                MessageBox.Show("Email is valid.");
            }
            else
            {
                MessageBox.Show("Email is not valid.");
            }
        }
    }
}