Klax Follow‑Up Email Marketing

A good deal of functionality in the app - provides options for a broad range of e-mail follow ups including cart abandonment, fullfillment, etc.. It's nice that they already have templates built out, so you don't have to type an email from scratch - you can just edit theirs. Also, they have great customer service!

The free plan is still valuable - I encourage you to download it and give it a try.