How to send Mail Using SMTP?

Question

So far I have this CODE for email validation and a Mail to send Using SMTPClient However it won't work ,it won't send to the gmail stated. But i think there is no problem with my code. I need some help to make a way for sending Mail .

string validEmailPattern = @"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"
      + @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)"
      + @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";
            Regex ex = new Regex(validEmailPattern, RegexOptions.IgnoreCase);

            if (ex.IsMatch(TextBox1.Text))
            {

                MailMessage m = new MailMessage();
                m.From = new MailAddress("[e-mail]");
                m.To.Add(new MailAddress("[e-mail]"));
                m.Subject = "Try";
                m.Body = "TEST";

                SmtpClient smtp = new SmtpClient();
                smtp.Host = "smtp.gmail.com";
                smtp.Port = 587;
                smtp.Credentials = new System.Net.NetworkCredential()
                {
                    UserName = "[e-mail]",
                    Password = "********"
                };
                smtp.EnableSsl = true;
                smtp.Send(m);

Answer 1

Change Your smtp.Host = "yourdomainname.com";

Answer 2

Try this code after  **smtp.EnableSsl = true;**

string validEmailPattern = @"^(?!\.)(""([^""\r\\]|\\[""\r\\])*""|"
  + @"([-a-z0-9!#$%&'*+/=?^_`{|}~]|(?<!\.)\.)*)(?<!\.)"
  + @"@[a-z0-9][\w\.-]*[a-z0-9]\.[a-z][a-z\.]*[a-z]$";
        Regex ex = new Regex(validEmailPattern, RegexOptions.IgnoreCase);

        if (ex.IsMatch(TextBox1.Text))
        {
            SmtpClient smtp = new SmtpClient();
            smtp.Host = "smtp.gmail.com";
            smtp.Port = 587;
            smtp.Credentials = new System.Net.NetworkCredential()
            {
                UserName = "[e-mail]",
                Password = "********"
            };
            smtp.EnableSsl = true;

            MailMessage m = new MailMessage();
            m.From = new MailAddress("[e-mail]");
            m.To.Add(new MailAddress("[e-mail]"));
            m.Subject = "Try";
            m.Body = "TEST";

            smtp.Send(m);
        }