What you mean by saying “protected” notes?
OK, let's try this: https://23gmt.nostr.technology/
A relay that only accepts kind:1 root notes only between 23GMT and 24GMT (also known as: right now) every day and deletes everything one hour after closing every day.
Also only "protected" notes are accepted so they don't leak.
Discussion
That they shouldn't leave the relay they were posted to against the will of the author: https://nips.nostr.com/70
Wow! That's very interesting. But where can I see if my client has implemented this nip?