protected void sendMail()
    {
        try
        {
            MailMessage mailMessage = new MailMessage()
            {
                Subject = contactSubject.Text,

                Body = contactBody.Text ,

                From = new MailAddress(contactEmail.Text),

                IsBodyHtml = true
            };


            mailMessage.To.Add(new MailAddress("atul39.chavan@gmail.com"));

            SmtpClient smtpClient = new SmtpClient();

            smtpClient.SendAsync(mailMessage, mailMessage);

            lblStatus.Visible = true;

            lblStatus.Text = "Your Request Submitted Successfully ..!!";
         }

        catch
        {
            lblStatus.Text = "Sorry Try Again Later..!!";
        }
    }

• Call the above created function on any of the event such as button click, page load etc.