I have compiled my official mail provider recommendations. With any provider, you must always use your own domain.
Good: Down to earth. Unlimited domains, storage, etc. Full marks for philosophical, ethical, and technical merits.
Bad: Difficult to set up. UI is a bit confusing. Advertises itself in your signature in the free plan. Apparently blocks VPN and Tor users (I have reached out to them about this).
Note: Was unable to evaluate their webmail
Good: excellent PGP support and good on other security fronts as well
Bad: requires google captcha, does not handle plaintext as well as I'd like, german leaks through into the english interface sometimes, too scatterbrained
Good: Goes above and beyond in support for various standards and protocols, handles plaintext email very well. Lots of good options for account security.
Bad: rough UI
migadu is hard to set up but is the best all-around offering. If you're security concious, mailbox.org has the best PGP support and good all-around security; runbox.com has good account security options but no built-in PGP support.
Evaluated but not recommended: disroot, fastmail, posteo.de, poste.io, protonmail, tutanota, riseup, cock.li, teknik, megacorp mail (gmail, outlook, etc)
For anyone with multiple domains, multiple senders, sending email programmatically, or simply with the knowledge and patience to do so - I recommend setting up your own mail server.
@sir A few more tips: You generally do not need a database server to manage multiple logins with virtual users. Disregard any tutorials that tell you otherwise. Postfix can authenticate via Dovecot and that can easily use a simple text file with user/auth/mailbox mappings.
Sieve scripts are extremely useful.
Instead of opendkim, you can also use amavis, which additionally takes care of validation and spam handling. Not difficult to set up.
(OT) And speaking of running your own DNS: It may be a good idea to run iodined so you have a way to bypass overzealous firewalls and captive portals/surveillance mechanisms of “free” public wifi networks.
Tōhō, free software and a cute mouse.