I fear for your finger joints, typing "fetchmail" 100k times each year!
Perhaps a daemon/bot to help automate things.

Seriously though, following your lead, I seem to be systematically
replacing reliance on conventional tools with low-footprint alternatives.
This does not mean low tech.

After replacing whatever init comes with the distro [salix, void, devuan],
with a 150 line sinit-based script [now using busybox and sdhcp]. This
allows me to setup the iptables firewall BEFORE starting the network
[almost every other distro take note]. This setup is mostly portable
across disparate non-systemd distros.

I also replaced the rats-nest that is initrd [thousands on lines of
sh-script] with a simple 120 line script that just does what I want [runs
e2fsck - yes I still use ext2]. I am sure adding extras bells like
encrypted root would grow it much.

Still, I also struggle to see how a "minimal" salix/devuan install needs
hundreds of packages.

And it continues.. but I still use Thunderbird and Firefox as I have yet
to grapple with the minimalist alternatives [surf, uzbl, mutt, ..].

Sorry about the length of this post.

jacksprat

addendum: references available on request.