### Properly configuring a mailserver
[These docs](https://nixos-mailserver.readthedocs.io/en/latest/setup-guide.html)
explains (in depth) how to configure [simple-nixos-mailserver](https://gitlab.com/simple-nixos-mailserver/nixos-mailserver)
and achieve a 10/10 [mail-tester](https://mail-tester.com) score.

Due to a lot of internet politics self-hosting a mail server isn't always
super easy. TLDR a lot of VPS subnets get abused and get registered on blacklists.
You should test your IPv4 address (or domain) on [MxToolbox](https://mxtoolbox.com/blacklists.aspx)
first. If you're not blacklisted you you'll only need to worry about writing
out DNS records (very specific ones that avoid your emails going straight to spam).