static function onInvoiceStarted(Am_Event_InvoiceStarted $event)
 {
     $invoice = $event->getInvoice();
     $event->getDi()->emailTemplateTable->sendZeroAutoresponders($invoice->getUser(), $invoice);
     if ($invoice->first_total > 0 || $invoice->second_total > 0) {
         return;
     }
     if ($event->getDi()->config->get('send_free_payment_admin')) {
         $et = Am_Mail_Template::load('send_free_payment_admin');
         if ($et) {
             $et->setUser($event->getUser())->setInvoice($invoice)->setPayment($event->getPayment())->setInvoice_text($invoice->render());
             $et->send(Am_Mail_Template::TO_ADMIN);
         }
     }
 }