If the re-publisher uses the same receiving address, it seems that two envelopes are not necessary. Instead, a single envelope can include two receiving addresses (a feature supported by Nostr). The first receiving address is the re-publisher's receiving address, and the second address is the true recipient's nearly one-time receiving address. The re-publisher receives the message from relay X and then forwards it to relay Y. The recipient retrieves the message from relay Y.
Discussion
Not sure I follow on the two receiving addresses. Wouldn’t we want two envelopes so it’s hard for outsiders to trace the path of the message?
In the `p` tag, multiple recipient addresses can be included. A single envelope can list two addresses: one is the re-publisher's address, and the other is the recipient's one-time address (which already resolves the metadata issue at the application layer). This is the solution with the least amount of changes.
Using two envelopes (outer and inner) is also an option, but it involves slightly more changes compared to the first solution.
Tried to capture a history of the proposals for it cause curious why it seems to have stalled: https://blog.yonson.dev/log/2025-01-vol1/
Could see it having some tricky UI issues though for something like chat use cases.