Retention.com is a great way to build your email list and cut costs, especially if you use Klaviyo as your ESP. They fill a gap allowing you to drive revenue and collect emails from the majority of your traffic that doesn't submit to an email popup. They also provide a self-serve competitive offering to tools like Wunderkind if you're not looking for full white glove service and the high price tag that comes with it. The people on their team I've interacted with have been very friendly and willing to help out. Review collected by and hosted on G2.com.
Works best if you're on Shopify. We're currently migrating to Shopify Plus but previously integrated while on Salesforce Commerce Cloud and things took a while. They also don't yet have a "checkout abandonment" option that would send the entire contents of a users cart. This would likely drive much better performance than the "add to cart" event they have which triggers off just the first event the user adds. It would also be great to get some visiblity into the match rate on your site to compare to other solutions like Wunderkind. Review collected by and hosted on G2.com.
