Honestly, it's about time Postfix gets replaced with a modern email server. It's a dinosaur designed around 1990s UNIX, with dozens of leftover footguns eagerly waiting to go off.
The fact that it even allows local mail submission or trusted subnets is already problematic, if you ask me. It is 2023, email should only be allowed after proper authentication & authorization!
I don't want a custom OIDC provider, I want to log in with a regular username and password!
Setting up OIDC might make sense when you're a larger business, but when you're a hobbyist with one account and a handful of machines having to jump through such hoops is a massive PITA.
The only thing which bothers me is their lack of proper user accounts.
I don't mind registering for a service like Tailscale, but I definitely don't want use a Google/Microsoft/whatever account for it!
Headscale might be a solution to that, but for something designed to essentially punch through most of my security I would rather prefer something well-supported by a larger player, tbh.
Wow, that looks amazing!
Have you also considered routing networking through the backplane? That would essentially get rid of all per-node wiring.
Of course Postfix supports auth, I'm not disputing that.
The problem is that it also supports completely anonymous submission from localhost and from local networks, and there are half a dozen ways to accidentally turn your server into an open relay. This made sense in the 1990s when every machine was hosting its own mail server for the two dozen local users, but we don't live in that world anymore and support for it should've been removed already. If you're using it something is going seriously wrong in your setup, so why is it allowed at all?
I haven't looked too closely into it, but something like Stalwart seems closer to my expectations: just a no-nonsense batteries-included secure-by-default mail server.
There are also dozens of "mail in a box" setups out there who try to do the same thing, but they all end up being Rube Goldberg machines built on top of legacy software.