Yup we agree on that. This pattern is actually the most sensible approach to support privacy. Whatever happens in transmission.

The easiest implementation of this is that the recipient of an infringing message flags it from its local client. At that point it’s not encrypted if their claim of e2ee is true.

It also means that only parties involved in the message exchange can flag / report them.

Corporations are often not so monolithic ; the guys doing abuse are likely not the one who try to milk users (looking at you marketing).

Any reported message ? Back when I was doing anti spam at my ISP we could read reported spam from our customers. Obviously not all mails from / to the customers. That would be way disproportionate.