I’ve been self hosting email successfully for 20 years. My goto article for this question:
https://poolp.org/posts/2019-08-30/you-should-not-run-your-mail-server-because-mail-is-hard/
TLDR;
- Mail is not hard: people keep repeating that because they read it, not because they tried it
- Big Mailer Corps are quite happy with that myth, it keeps their userbase growing
- Big Mailer Corps control a large percentage of the e-mail address space which is good for none of us
- It's ok that people have their e-mails hosted at Big Mailer Corps as long as there's enough people outside too