Seriously, try https://www.uniboxapp.com/. I've been using it on my Mac since beta, and now they have an iOS version. I haven't looked back since. It organizes email by person, like text messaging.
Thanks! Looks like a neat app for personal use; doesn't seem to be geared for my own use case though (multiple domains/companies). And while they might or might not stay in business, I'm reasonably sure that mail.app won't be abandoned by Apple.
Does it have email tracking, snooze/read it later functions? Site seems to be sparse on details. I've been quite happy with Polymail thus far, but organising emails by person would be amazing.