domain email programming

 SmtpClient smtpClient = new SmtpClient("domainname", 25);

            smtpClient.Credentials = new System.Net.NetworkCredential("domainemail", "password");

            smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;

            MailMessage mailMessage = new MailMessage("domainemail", tomailidcontrol);

            mailMessage.Subject = "Thanks For Registration";

            mailMessage.Body = "Dear User" + "<br>" + "Your OTP is :" + " " + Label5.Text;

            mailMessage.IsBodyHtml = true;

            smtpClient.Send(mailMessage);

            Label1.Text = "OTP Send to email please check Inbox / Spam";