I'm really looking forward to what DHH can do with https://hey.com/. My aim with an email provider is that I trust it. A non-bootstrapped company with a founder outspoken against privacy issues seems a good place to try.
no migration path, you start with a clean slate web based only, no imap access (not sure of smtp) no custom domains on day 1
Maybe this will change as they delayed the launch due to covid-19 but right now it's something I, and I assume many others, will watch from afar as its missing crucial elements.