I find this all moot. Not useless (because it's another layer of defence in depth), but still recoverable. A real end-to-end encryption is such that the transp

I find this all moot. Not useless (because it's another layer of defence in depth), but still recoverable. A real end-to-end encryption is such that the transport intermediary only passes opaque blobs, and won't be able to decrypt them to save the CEO's life. Everything else is sparkling obfuscation. But even with that level of unbreakable content encryption, the metadata, which has to be accessible to the intermediary in cleartext, could blow enough covers.