I would be really interested in this if it had a focus mode, that hides e-mails and delivers them to me in batches. I loved Tempo[1], but unfortunately they ran out of money, which shows how tough this space is.
Shortwaver here! We've had a few former tempo users switch over to Shortwave and are enjoying the product. We have a few features with bundles that we really want to build that would allow you to replicate a Tempo like workflow of triaging your email in batches.
[1]: https://www.yourtempo.co