Will Lemmy spam become like email spam? - sh.itjust.works

My understanding of federation is that it’s like email. If one server is misbehaving, then they get defederated. So how come email spam still exists - why don’t spammer domains get defederated? It seems like we’ve got the worst of both worlds, where it’s hard to get your emails relayed when you run a small email server, and easy to get them relayed if you’re a spammer. Is there anything about Lemmy’s architecture that will prevent this problem?