Hosting your own email is a bad idea. Hosting OTHER PEOPLE’S email is a REALLY BAD idea. Self-hosting mail on a vanity domain is a good exercise to learn how SMTP, DNS, IMAP and other protocols interact.
If you don’t like Google, Apple, or Microsoft then sign them up with Proton or another hosted provider. You don’t want to be the reason someone lost income because they missed out on a critical email from a client or their job application was blocked because it was sent from a host with poor reputation.