Information on all registered domains are available to the public via what is known as the "WhoIs" database.
Whois databases enable people to determine who has registered any given domain, and how to contact them.
Whois databases respond with the complete listing for that domain, including email contact information where available.
Note that there are different WhoIs databases for each country.
If you wish to search on a country-based domain [ie., intervtions.com.au] then you need to search in the relevant countries WhoIs database, the Australian WhoIs database.
These country-based databases are maintained by the Network Information Centre(NIC) of the country in question; in Australia the NIC is the auDA.