See this howto: https://poolp.org/posts/2019-09-14/setting-up-a-mail-server-with-opensmtpd-dovecot-and-rspamd/

I have delivery to the inbox of all major providers using this. Email is not that hard…

Been hosting my own email for over 20yrs. Get a vps at some reputable hoster, and make this a dedicated mailserver. Be sure to setup all dns records that are required, and rollout antispam measures.

Thing is, you grew up in the pioneering age of computing, and in that time you needed to do everything yourself. This gave you a bunch of skills for free, that are hard to do today, because most of the hard stuff is automated away and snuck behind a gui and/or containers.

Alma, Talos, OpenBSD

OpenLDAP multi-master with a bunch of custom schemas.