vmse04.mailcluster.com.au has no MX records.
Question and response
Question
dig vmse04.mailcluster.com.au. MX
Answer
The response has no answer records.
Authority
mailcluster.com.au. 3600 SOA ns1.digitalpacific.com.au. hostmaster.mailcluster.com.au. 2025102939 7200 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0