sometimes we have to send automated nip-17 messages, using codes. for example in nostr-tools on npm, we tried a lot but when we try to decode it we get invalid mac for no reasons. or sometimes a client event amey won't show some of them. i believe this one is because of invalid outbox model usage on some clients. also, are they energy efficient? when i look at the spec we do a lot of cryptography.

The ones with invalid mac I get are very old. Probably from clients doing tests. But we should keep an eye on it. Outbox model is irrelevant as NIP-17 has its own relay model. It doesn't use NIP-65 at all. They are not supposed to be energy efficient. They are supposed to be private at the expense of more energy.