I am currently midst sending a newsletter to 12782 subscribers, it has been going since 3:00am this morning and now it is 22:41, but has only sent 4740 emails.
Investigating further it has come to my attention that the rate has been limited to 20 here:
public function scheduledSend($schedule)
{
$countOfQueue = 3;
$countOfSubscritions = 20;
/** @var Mage_Newsletter_Model_Resource_Queue_Collection $collection */
$collection = Mage::getModel('newsletter/queue')->getCollection()
->setPageSize($countOfQueue)
->setCurPage(1)
->addOnlyForSendingFilter()
->load();
$collection->walk('sendPerSubscriber', array($countOfSubscritions));
}
In app\code\core\Mage\Newsletter\Model\Observer.php
I have tried searching online but cannot find why there is such a limit.
Moreover, not sure if it has a contributing factor but my cron and smtp pro settings are as such: