If you google "C# send mail", you'll get 708 thousand results back. Here's a code snippet from one of them.
try
{
MailMessage mail = new MailMessage();
SmtpClient SmtpServer = new SmtpClient("smtp.yourdomain.com");
mail.From = new MailAddress("your_email_address@yourdomain.com");
mail.To.Add("to_address@domain.com");
mail.Subject = "Test Mail";
mail.Body = "This is for testing SMTP mail from GMAIL";
SmtpServer.Credentials = new System.Net.NetworkCredential("username", "password");
SmtpServer.Port = 587;
SmtpServer.EnableSsl = true;
SmtpServer.Send(mail);
}
catch (Exception ex)
{
}