In magento 1.9.1.0, magento has added new feature, they store the order email in “Core_email_queue” table to send the mail of order. we have to set the cron.php in server.
The corn.php file set the “core_email_queue_send_all” in cron schedule table. when crone execute the “send” method called from Mage_Core_Model_Email_Queue. It send the mail to customer.
So above fix is working without any change in core file.
