With Arch, installing a package just unpacks the package files and runs a few innocuous post-install hooks, mostly to rebuild indexes (mandb, fontconfig, etc.) and compile DKMS-based kernel modules. But nothing potentially destructive like `systemctl start postfix`.

Also, it installs exactly what you want, instead of dozens of tangentially-related "suggested packages". If you `apt install rsyslog`, it pulls in an entire MTA because somewhere deep in rsyslog, there is an option that might send emails, so Debian in its unending wisdom determines that you MUST HAVE an MTA beyond this point. In Arch, `pacman -S rsyslog` installs just rsyslog and a few required shared libraries.

So does Debian, if that's what you tell it you want (either on the config file or as a CLI argument). Even without that, while it may suggest a full MTA by default, you can ask it for another solution and it'll suggest a simple mailer (like bsd-mailx).

I don't dispute that Arch's defaults guide you to a simpler system, but it's not really hard to start from Debian netinstall and add just what you need, package by package.

Exactly. The correct solution for me is "no mailer at all".