I don't feel like I "settled" for Postfix. The configuration is quite simple, the documentation is great, and it's been battle-tested for decades.

I have basically no experience with Javascript or web stuff, and the last thing I want to do is figure out some leftpad-style NPM package dependency while my mail server is down. Maybe I'm just an old-school Unix guy at heart though - running a JavaScript interpreter on a privileged port just doesn't sit right with me.

If you want "pain to configure and modify", take a look at sendmail, which was the standard for decades.

Postfix is a breeze to work with in comparison.

I don't agree. Sendmail definitely has the weirder config file syntax, but (having set both up multiple times) both have the exact same setup technique—reading through the manual looking at the config options and copying/pasting the lines into the config.

That same technique can be applied to basically anything.

I've setup both multiple times, and have worked with Sendmail since 1994. Postfix config files are much simpler.

To configure sendmail, you have to do extra layers of weirdness, like deal with "m4". That's mental overhead you just don't have with Postfix.

There's not really any extra layers of weirdness unless you're digging down into the nasty .cf files (which you probably never ever need to do). The m4 is just a detail (so you end up commenting with "dnl").

The relative complexity of the files is about the same—my postfix server config is roughly the same number of lines as my sendmail server config. And each line is just a single conf thing. Sendmail isn't really more complicated at all. It's just ugly.

Did not know Haraka, looks interesting.

Do you use it together with an imap server (like dovecot)?

Not yet no. But curious about such a setup as well.