Why would emails be ephemeral? I see the argument he and presumably you are making in terms of chats, though I disagree with it both in terms of what the law currently is and in what it should be, but email? Mail isn't ephemeral.

When you are having a conversation in person and you don't know it is being recorded, you have an expectation that it won't be recorded because that is the default. Do you have an expectation by default that your chat system, slack or whatever irc you use is not accessible by anyone ever again, once you close the client? I don't because that hasn't been the case for most chat clients ever.