this is one of the "directory" event kinds that i talk about, events that should be broadcast everywhere, because they provide information about the addresses of things that need to be accessible everywhere

they are small compared to follow lists, i think the proper relay behaviour is to accept them if it has old copies also 

 Some of them are massive (20+) relays because some clients just import everything from kind3 automatically. We need to find a way to discourage that.  

 turning these lists into CRDTs is key to cutting down this... follows, relay lists, mailboxes, all of them could be add/subtract ops one per time

i forget the nip number, maybe 87? there is some proposal for this that applies this and extends the capability of lists but i'm not sure if relays have been added to that