public bool SendOrders(Customer customer)
{
  if (customer == null)
    throw new ArgumentNullException("customer");

  if (customer.CustomerID  <= 0)
    throw new ArgumentException(
      "Customer must be registered.", "customer");

  if (string.IsNullOrEmpty(this.SmtpServerName))
    throw new InvalidOperationException(
      "SMTP server name not initialized.");

  if (!NetworkInterface.GetIsNetworkAvailable())
    throw new Exception("Network is not available.");
    
  // Implementation skipped...

  return HasErrors;
}