Honestly, get a small VM at openbsd.amsterdam or another good hoster and just do it yourself. OpenBSD has outstanding documentation, standing up SMTPD and Dovecot there is super simple, especially for a single user and not a whole group or family (where LDAP or Kerberos would be warranted). Just take initiative and own your data. Does it cost a little bit upfront time? Sure, but maybe just weekend. Does it require a little maintenance here and there? Sure. But still cheaper than paying for fastmail or waiting for fastmail to also exploit your data because the shareholders said so....just own your data.
I like Fastmail with my own domain for personal email, but the reality is nothing is a complete replacement for a Google account, given how tied in it is with auth and the whole Google ecosystem. I still have to use Google for work.
Proton is another one people often suggest. Hey.com sometimes too. No experience with those myself.
There are other options (such as the big guys, iCloud mail or Outlook.com), but aside from self-hosting (which I don't want to spend time maintaining just for my personal mail), I personally haven't seen much outside of those ones that are recommended often.
Assumedly you need an email hosting service to place behind your domain, correct? Or do you self host an email server? If you are completely self-hosting, how do you deal with being marked as spam by large spam filter organizations for being a low-trust sender?
In daily practice you don't. Unless you host in a DC with lots of spam. Use small but trusted hosters.
But as long as you get SSL/DKIM/SPF and the other stuff right, and it's not THAT difficult, then most hosters will let you through. Unless it's German Telecom, because for some reason t-online.de decided to only allow emails from hosters they whitelisted and there's a whole approval process which even requires registering with them with an email that is NOT from your domain and even a fax, but honestly fuck anyone using that domain.
I long made a "spam/unimportant site verification " account, so that's set.