MailMessage msg = new MailMessage();
msg.From = "email address";
msg.To = txtMailTo.Text;
msg.BodyFormat = MailFormat.Text;
msg.Subject = txtSubject.Text;
msg.Body = txtMessage.Text;
SmtpMail.SmtpServer = "your smtp mail server";
SmtpMail.Send(msg);
Use it, it's working fine.