self hosted mailserver here (on an old, dedicated vps)… just dovecot/postfix/mysql and the usual (amavis & spamassasin) - if i need to add/edit/delete users or domains, that’s just a bash script.

there’s lots of other options already mentioned, but you could also consider aws for this: you set your domain up with them (or verify it), set SES to forward inbound mails to wherever you want, and set your mailclient to send out through ses.

antispam & dkim/dmarc/spf included.