We ran a Marketo email marketing benchmark study last year and are running a new one this year.
You can download it here: knak.
It doesn't have specific industry breakdowns but we will try and get that this year. If you'd like to contribute to this years study, please do so here: 2019 Marketo Email Marketing Benchmark Report Survey
We rely on the data provided by Smart Insights here: https://www.smartinsights.com/email-marketing/email-communications-strategy/statistics-sources-for-email-marketing/
Additionally, we maintain an internal benchmark report of our email campaigns for different subscriptions, regions, and audiences.