ns1.bulletproof.net.au has no MX records.
Question and response
Question
dig ns1.bulletproof.net.au. MX
Answer
The response has no answer records.
Authority
bulletproof.net.au. 300 SOA ns0.bulletproof.net.au. hostmaster.bulletproof.net.au. 1772493973 108001 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0