I haven't mentioned it because it's a *another* paid relay, however Nostr Plebs does have a relay that can help with spam mitigation too. The only caveat is that you need to be a Nostr Plebs registered user and currently be using your nostrplebs.com or another Nostr address purchased from us to be able to write to our relay. It's a little different than most.

wss://relay.nostrplebs.com