Getting feedback about a product/service can help you improve its quality and make your store more efficient and reliable for your customers. Providing feedback mail for your customers shows that you are concerned about their opinions and are always open to new ideas/suggestions.
Keeping that in mind, you can use the Feedback Mail feature to enable your customers to submit feedback about a product after it has been delivered.
To enable this, go to Your Apps -> Feedback Mail
Click on the Enable button and then click on the Save button.