I also want to get away from Google services as much as possible.
Right now I'm considering using Amazon Workmail since I use AWS for a ton of things, though I guess that would put me in the AWS ecosystem.
What do you use?
At least that’s what I did
There are only three businesses that have ever blocked email from or to me and two of them were cellular service providers. They all appear to use the same anti-fraud service. [Edit: and Tractor Supply]. I use that when I want to email someone that I am certain will abuse my email address or domain or if I want to receive a massive file or set of files from someone. That keeps the noise off Fastmail which I also use, mostly for family and business related stuff. With Fastmail I pull the emails off the server as fast as I can using Thunderbird in the event they get popped by citizen or government attackers such as the AU government should they do mass surveillance some day. Fastmail is under AU jurisdiction. As a side note, Thunderbird makes PGP encrypting emails trivial.
Another nifty thing one can do on their own mail server is pin TLS certs of specific people or businesses to see if something has changed. Not everyone would need this but monitoring certs with bash+openssl is super easy. It's useful for fringe cases.
fastmail for a mailing list / sports team thing that I help run. local hockey league stuff. someone else set it up but it works fine and we keep using it.
protonmail for personal email, previously tutanota before that