private void button1_Click(object sender, EventArgs e)
{
            if (textBox1.Text.Trim() != "")
            {
                Match rex = Regex.Match(textBox1.Text.Trim(' '), "^([0-9a-zA-Z]([-.\\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\\w]*[0-9a-zA-Z]\\.)+
                 [a-zA-Z]{2,3})$", RegexOptions.IgnoreCase);
                if (rex.Success == false)
                {
                    MessageBox.Show("Please Enter a valid Email-Address ", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
                    textBox1.Focus();
                    return false;
                }
                else
                {
                    return true;
                }
            }
            else

            {
                return true;

            }

}