protected void Page_Load(object sender, EventArgs e)
{
 try
 {
  MailMessage message = new MailMessage(
    "from@example.com", 
    "to@example.com", 
    "Some Important Message", 
    "This is a test message and it's not that important.");

  SmtpClient client = new SmtpClient("your.smtp.server.com");

  System.Net.NetworkCredential credentials = new 
    System.Net.NetworkCredential(
      "username", 
      "password");

  client.UseDefaultCredentials = true;

  client.Credentials = credentials;

  client.Send(message);
 }

 catch (Exception ex)
 {
  Response.Write("Whoops! Couldn't send the e-mail: " + 
    ex.ToString());
 }
}