mx.cp2.c55.com.au has no CNAME records.
Question and response
Question
dig mx.cp2.c55.com.au. NS
Answer
The response has no answer records.
Authority
c55.com.au. 10800 SOA ns1.c55.com.au. c.c55.com.au. 2026022306 3600 1800 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0