Ask HN: Local (LAN) email server for homelab?

I have been playing with the idea of developing a simple email server for my LAN homelab, for 20-ish servers, VMs and containers to send regular messages about status, self-tests, errors, etc.

For a basic Unix-type box, email still seems like one of the most accessible, ready-out-of-the-box protocols for a machine to send messages about status.

Most of the discussion about self-hosting email focuses on deliverability and spam concerns, but that would obviously not be an issue in this setup. My understanding is that the architecture would be overall quite simplified and manageable.

Does anyone do this already?

And who knows, maybe other people living in my household would find it quaint and amusing to use a local email system to send messages back and forth ;)