只需按一下“提交”按钮，就无法添加超过994个条目

Question

I send a newsletter to about 2560 emails. The php script creates an entry for each e-mail in a table, and every 15 minutes 50 mails are sent so the server doesn't get busy.

When I send the newsletter to all 2560 emails, I get a 404 page. When I only select my Email, everything goes as it should. I'm thinking there is some limit that prevents MySQL from adding that many entries. I can add any more than 994 emails, I get the 404 error. How can I resolve this?

---

I select users from left list > click right arrow > user gets moved to right list and then they all get selected(from 'send to' list) when I press submit and get either a 404 error(when over 994) or a succesfull message.

   $conn =  sfContext::getInstance()->getDatabaseManager()->getDatabase('doctrine')->getDoctrineConnection(); 

    ini_set('memory_limit', '1024M');
    set_time_limit(0);
    try 
    { 

    $conn->beginTransaction();

    foreach ($to as $email => $name)
    {
      if (is_integer($email))
      {
        $email = $name;
      }

      $hash = substr(md5($email), 0, 5);

      //save to cron job

      $html = str_replace(array('[+hash+]', '[+email+]'),array($hash, $email), $content);

      $query = $conn->prepare($sql = "INSERT INTO CronEmail (sendto_name, sendto_email, from_name, from_email, subject, message, created_at)
       VALUES (:sendto_name, :sendto_email, :from_name, :from_email, :subject, :message, :created_at);");


      $query->execute(
        array('sendto_name' => $name,
            'sendto_email' => $email,
            'from_name' => "Newsletter " . $fromsite,
            'from_email' =>  "[e-mail]",
            'subject' => $newsletter->getSubject(),
            'message' => $html,
           'created_at' => date('Y-m-d H:i:s'))
       );

    }

    $conn->commit();

    }catch (Doctrine_Exception $e) { // Rollback if transaction fail 
      $conn->rollback(); 
      echo $sql;  
      echo $e->getMessage();
      die();
    }


    $this->getUser()->setFlash('alert', '<div class="alert_ok">Newsletterul a fost salvat si va fi trimis!</div>');

    $this->redirect('newsletter_send/index');
  }
}