Specifically:

A technical assistance request that relates to an agency, or a technical assistance notice that relates to an agency, or a technical capability notice that relates to an agency, has no effect to the extent (if any) to which it would request or require a designated communications provider to do an act or thing for which the agency, or an officer of the agency, would be required to have or obtain a warrant or authorisation under any of the following laws:

                     (a)  the Telecommunications (Interception and Access) Act 1979 ;

                     (b)  the Surveillance Devices Act 2004 ;

                     (c)  the Crimes Act 1914 ;

                     (d)  the Australian Security Intelligence Organisation Act 1979 ;

                      (f)  a law of the Commonwealth (other than this Part) that is not covered by paragraph (a), (b), (c) or (d);

                     (g)  a law of a State or Territory.*

Don’t know Australian law, but for a warrant you need to demonstrate probable cause in front of a judge. And that’s a pretty high bar.

Here’s Tim Cook making that point: https://m.youtube.com/watch?v=rQebmygKq7A

With an email provider you don't need a back door to get somebody's emails.

I said that to you (a user who wouldn't be the target of a warrant) there isn't a practical difference if you're targeted. You wouldn't be able to mount a defence in court anyway.

But of course, it being easier is a very serious problem from a societal perspective.

IANAL.