I use POPFile, open source software that classifies email into whatever categories you set up using a Bayesian algorithm (so you train it). It works as a proxy so it does it when your download email, so not a solution to your inbox filling up unless your can figure out how to run it on the server automatically.
It tags the email with a header and I use Thunderbird filters to move mail to folders for spam, adverts, political spam, and regular inbox.
It's abandonware but it still works and doesn't really need any more features IMO.
I have no idea about Navidrome, but I completely agree with the gist of this article. Actively choose the music you listen to. When the music you've chosen has run out, if you're not motivated to make another choice, let the music stop and enjoy quiet for a while.