We are facing a problem customer is not receiving order confirmation email. It was fine one day ago but now this problem occurred.
WE didn't change any setting
Customer can receive Forgot password Email but not order confirmation email
Starting with Magento 1.9.1 the emails are not being sent directly during checkout but instead are being queued. The queue is being processed via your Magento cronjob - please ensure this has been set up and is running correctly.
The extension AOE_Scheduler can help you in confirming that your Magento cronjob has been configured correctly and is running.