So you call it easy to configure together 7 different systems just to get a working mail server?

Yes, with the qualification that I brain farted on cyrus (not using that for mail) and you can just as easily skip the two dkim packages (which were a bit tedious to figure out).

Postfix works out of the box. Diffing the stock main.cf with mine the differences are: new additions that never made it into my main.cf, a few lines to enforce stronger TLS ciphers (optional), a manual blacklist (optional), virtual domain stuff (also optional), milter lines for dkim and spf (optional), a line to deliver to procmail instead of directly to a mailbox (optional), and a line to enable mail relay access to authenticated users (also optional). You could install postfix and have a good experience out of the box.

Dovecot: a line to enable verbose process names (optional), a stanza to enable the SASL backend (optional), a line to specify which keys to use for TLS (mandatory), a few lines to up per-user limits (optional). Setting up SSL is going to be the hardest part, and even that shouldn't be too bad.

Procmail: A couple lines to pipe everything to spamassassin and deliver to a mailbox or a spam folder. This may be considered tricky by some but procmail is ancient and, in my experience, examples abound.

Spamassassin: No changes. In fact I think I've ripped out most of my custom config except for some whitelist stuff.

Four packages and you'll have a working SMTP and IMAP server. No, I don't think that's difficult. Wrangling an OpenLDAP install, sure that's difficult. This? No. Scaling it out to hundreds or thousands of users is trickier, but not something the typical home user would need to bother with.

For everything above there's actually quite good documentation. What's difficult is figuring out which packages to install in the first place and deviating from the stock configurations for the little extras you may want, but even then the big challenge is in taking the time to read the documentation and figuring out which features you want. Maintenance is trivial, although I probably should update my postfix config to get it in line with the current config syntax.

Dovecot uses PAM for authentication, and so any user with an account can log in and access their own mailbox and send mail out. The biggest downside is that because I'm deviating from the default FreeBSD configuration for postfix I'm on my own in terms of updates.

I should also clarify the above statement about moving it all into a jail -- I mean a jail managed by (in this case) ansible. Yes, if you just slap something together it will be brittle no matter what stack you choose. Ansible + Jenkins + Jails make it much easier to manage changes.

Edit: Oh yeah, and I've thrown procmail in there for good measure.

But I've been self-hosting mail services for over a decade at this point. It's seen a variety of permutations including some with Sendmail, some with postgres backed lookup tables for virtual hosting, and so-on.