Does this Abandoned Cart Email extension work with guest checkout?
Yes, our Magento Abandoned Cart extension works for guest users too. If a customer enters his/her email on the checkout page, but then interrupts the checkout process, the extension captures this email with AJAX and immediately saves it. Therefore, you are able to send abandoned cart emails to guest customers who are not registered and haven't completed the purchase.
According to the statistics, you may find helpfull the following question about guest checkout.