Not sure it will fly much
When they first suffered their DDOS attacks I set up an account as much for fun as anything. Recently with mad Mays actions and the Orange one over the way I started wondering if I would use it in anger. Logging in with good strong passwords and then decrypting the mailbox is not too difficult but I cannot imagine a. n. user being prepared to go through the process of creating strong passwords and storing them in keepass/whatever. Then having to go through the dual process of logging on and decrypting the mailbox.
I am still glad that they are there. Could email standards be changed so all emails are encrypted by default? Ha!