I'm sending email using smtp services in my c# windows application. I have to perform in a best way to reduce the email bounce rate. I have to check the provided email address is valid or not. I'm using the code.

```
    private void btnCheckValid_Click(object sender, EventArgs e)
        {
            if (isRealDomain(textBox1.Text.Trim()) == true)
                MessageBox.Show("Valid Email Address!");
        }
        private bool isRealDomain(string inputEmail)
        {
            bool isReal = false;
            try
            {
                string[] host = (inputEmail.Split('@'));
                string hostname = host[1];

                IPHostEntry IPhst = Dns.GetHostEntry(hostname);
                IPEndPoint endPt = new IPEndPoint(IPhst.AddressList[0], 25);
                Socket s = new Socket(endPt.AddressFamily,
                        SocketType.Stream, ProtocolType.Tcp);
                s.Connect(endPt);
                s.Close();
                isReal = true;
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                isReal = false;
            }

            return isReal;
        }

```

By checking the real domain I can identified the Hosted IP but the email address is created on the host or not.

with regex (regular expression ) I can valid only format.

So my question is how to find only valid address of any domain in c#.