I believe relays send events to each other as well..
Login to reply
Replies (1)
Not if they are standard compliant: "A relay doesn't talk to another relay, only directly to users."
Source: 
GitHub
GitHub - nostr-protocol/nostr: a truly censorship-resistant alternative to Twitter that has a chance of working
a truly censorship-resistant alternative to Twitter that has a chance of working - nostr-protocol/nostr