mx.ozlabs.org has no CNAME records.
Question and response
Question
dig mx.ozlabs.org. NS
Answer
The response has no answer records.
Authority
ozlabs.org. 60 SOA ns.ozlabs.org. hostmaster.ozlabs.org. 2025123398 14400 3600 2419200 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0