Given that they store all of your data in plain text, probably run your own email server or use a different service. That's not really changed by this new law and was always the case.

I use fastmail as well, I like their ui a lot. I certainly treat it as the stockpile of plain text messages tied to my real life identity through my credit card that it is though.

I'm an Australian privacy-obsessed Fastmail user, and use them for my family domains and all our primary email. I'll keep using them, because email isn't private in the first place. Any more than snail mail is. Both can be intercepted and read by authorities without you knowing.

For secure communications, you shouldn't be using email in the first place, so these new laws don't change much in that regard (in my understanding, I'm still catching up on the new laws because I have limited internet access right now, I'm happy to be corrected).

This is increasingly not true. SMTP-over-TLS is now the standard, and unless you are trying to imply that TLS is broken, email is far more secure than it used to be.

If it's not end-to-end encrypted, it's not secure in the sense OP clearly means.

Correct: if either mail server is compromised by the government then it may as well be plaintext.