The spam to my own Tor relay operator email address (same one as in this list) isn't meaningful in volume. I haven't seen any amounts that a delete key couldn't easily handle.

In my experience, you should be careful with spam filtering, as you could end up dumping abuse complaints that you wanted to see and maybe respond to, or have legitimate relay list email not come through. I ended up having to whitelist some stuff for this list to work right because of automatic spam behavior of this mail service.

It's not like the sight of spam email in your tor relay box is toxic to your workstation. It's usually obvious from the subject what it is, and that it can be safely and immediately deleted.