John,
While I am not an expert at DNS entries and what is needed
for reverse DNS matching, I believe what you have to do is get the
mail MX record in whoever is hosting your DNS to read something
like mail.northsydneycc.com.au. You already have a zone file that
contains the routing for www.northsydneycc.com.au, you just need
the appropriate MX record. Though, do you have your own mail
server? Or do you use someone elses?
I will, however, defer to someone else who really knows what
they're talking about. This may not be the solution to your
problem, but I
think it is.
It is also possible that you have gotten on a blacklist
somewhere that hotmail uses. Have you had any viruses lately where
your mail server has been used as a relay for spammers at all? Not
likely, cause you would have seen an error message that indicated
such, but possible I guess.
Swift