There is no “good open rate” that applies universally to all email marketing efforts undertaken by an online retailer.
Customers experience the email channel differently depending on their lifecycle stage, so general benchmarks are useless.
There are three dimensions that we use to benchmark open rates for eCommerce companies at Rejoiner: By customer lifecycle stage, by campaign trigger type, and by vertical industry.
As you’d expect, average open rates vary significantly by trigger. Here’s an aggregation of our open rate data from Q4 2018 by trigger: