s/Postgres/Postfix/ ??

In any case you should ask the author, as they are currently active on another discussion where they linked their article in a comment: https://news.ycombinator.com/item?id=16238501#16238845

>perlgod: I've spent years tweaking my mail server setup (Postfix, Dovecot, RSPAMD, LDAP...) and did a full writeup a few months ago. I've used other guides online but found most of the rest lacking on details