Sounds familiar

I also run a similar setup - Postfix and Dovecot mainly. I didn't find it all that difficult to set up for my single-user config (granted, it's of course more work than signing up for an email account somewhere).

A long time ago, I used to be a happy user of dspam - but that was abandoned at some point IIRC. Looking for a replacement when the time came to move to a newer distro release, I installed Rspamd - but never took the time to understand how to configure it. So for the last 10 or so years, I've been deleting 1-10 spam emails a day. Not too terrible IMHO, some are even somewhat comically funny. That's a very small minority though - most are just the same old boring scams and gone as fast as I can hit delete.

What stops most spam though seems to be the very basic DNS requirements on sending hosts - the HELO name needs to resolve to the IP it's connecting from, and that IP must have a PTR record. Most zombied spam senders don't meet these requirements, while the vast majority of legitimate email servers does. (I remember having to manually allow exactly one host to be able to receive emails from a large, well-known company that shall remain unnamed.)