ari.beta.aridns.net.au has no MX records.
Question and response
Question
dig ari.beta.aridns.net.au. MX
Answer
The response has no answer records.
Authority
aridns.net.au. 900 SOA ari.alpha.aridns.net.au. admin.tldns.godaddy. 1772210332 1800 300 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0