mx.ipng.com.au has no CNAME records.
Question and response
Question
dig mx.ipng.com.au. NS
Answer
The response has no answer records.
Authority
ipng.com.au. 83 SOA sy4.dns.ipng.net.au. hostmaster.ipng.net.au. 2026010201 10800 3600 604800 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0