I know, nobody wants to run their own mail server because hassle. It has gotten so complicated that engineers don't even want to fuss with their own mail server and would rather just pay to have someone else bother. But I found a very low-hassle way to do it. HestiaCP manages everything automatically, so you don't have to spend endless time manually configuring everything on the mail host. (https://hestiacp.com/)

0. Buy your own shiny, new TLD.
1. Get a cheap VPS at Racknerd. They have them for less than $20 per year. Find the deals at lowendtalk.
2. Install Debian on the VPS.
3. Install HestiaCP on the fresh VPS install.
4. Point registrar DNS to your VPS IP address as the custom DNS server.
5. Use the web interface of HestiaCP to add your mail domain and accounts.

Done.

You now control all your own unlimited email accounts on your own domain for about $30-50 per year. Plus you can host any other kind of apps, including your own fediverse instance, a tor node, a web server, etc. As long as your other apps are each run under separate user accounts, there is virtually no risk to your email privacy.

For the most part you do not need to manually configure DNS. Hestia does it for you. But make sure to put your TLD and static IP in /etc/hosts, and reboot, before installing Hestia. That will save you some head scratching.

It may take a few weeks for your new TLD reputation to get cleared with some other MX hosts. That's just the way it is now with all new domains. So for a few weeks you might get bounces sending to some hosts, but after a while that clears up as long as no new spam originates with your domain MX.