It's hard to say no. Only a few countries won't cooperate at all. And Australia is not likely to be one of them.
That is where an approach similar to "Protonmail" (this is not about them specifically) where only the user can gain access is the way to go. We had a similar thing a few years ago over at Bitcointalk. "They" were able to convince the powers that be to give them ALL PM's in the database. Those that were smart enough to have GPG'd all their messages, which I do, were not compromised. Any plain text PM's were summarily recorded and whatever consequences followed. The entire point is to enlist a service where ONLY the end user can gain access regardless of who acquires the database being sought. Its not like this is rocket science. Email providers just need to care about the end users. At the same time they escape certain liabilities by being able to provide all that they have, knowing the end user emails are still beyond reach.
