The Magento out of stock extension by FMEAddons allows you to connect with the specific customers and update them with the product availability. Customers can subscribe to the out of stock products and when these products are available for sale, an alert is then sent to the specific customers regarding their availability. This extension contains the subscription feature, which allows subscription to both guest and registered visitors. The email notification will be sent automatically as the out of stock products comes in stock. Admin can decide which products are to be opened for sale and which are kept out of stock on the basis of products subscriptions.