I probably shouldn't announce things before I've finished writing them but i'm pretty excited about this. Gossip will soon have an embedded mini relay tester that will tell you if a relay is suitable for outbox, private inbox, public inbox, or DM usage. I think the proliferation of many different kinds of relays for many different purposes has made the situation for end users very difficult, and this is going to help a lot... it is better than trusting a relay to tell you what it does. It will work for paid relays too (once you have paid) as it uses your keypair to test.