Back in Stock Alerts let shoppers sign up to be notified the moment a sold out product becomes available again. Instead of losing that sale, you capture the shopper's email (or name and email), and automatically email them when inventory returns.
How it works, in short:
A shopper visits a sold-out product page and sees a "Notify me" button in place of the buy button.
They click it, enter their email in a popup, and get a confirmation.
When inventory crosses a threshold you set, they automatically receive a "back in stock" email with a link to buy.
Everything is configured across four tabs when you create an offer: Design, Products, Email, and Subscribers. An offer stays in Not published status while you build it out, so nothing goes live until you're ready. Click Publish when it's ready for customers.