mail.dnstest.iprimus.net.au has no MX records.
Question and response
Question
dig mail.dnstest.iprimus.net.au. MX
Answer
The response has no answer records.
Authority
dnstest.iprimus.net.au. 500 SOA ns1.dnstest.iprimus.net.au. hostmaster.dnstest.iprimus.net.au. 2014080013 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0