Currently, Damus relay addresses spam issues by limiting the frequency of posting notes, while nos.lol uses proof of work to tackle spam.

Keychat relay uses "stamps" to solve spam problems and generate revenue.

If a user has a cashu sat balance, Keychat automatically attaches a stamp, which is 1 sat, to messages sent by the user.

The stamp is affixed to the event, and the relay is the first to receive the event. The relay then copies the cashu sat, accepts it, and forwards the message. nostr:note15sza0s4yrxzx35cn3cs5xarxd48h7tgc5eyy4x0ml98jqfrk92gswyvhc8