I mean yeah it should but you gotta follow the old saying "don't write when you can speak, don't speak when you can nod, don't nod if you can wink" or whatever. You have an expectation of privacy when sending physical mail for example, but it's still a bad idea to put a crime in writing if you don't have to. Even if it can't legally be used as evidence it can be read. We've seen that with 'parallel construction' from law enforcement