ns1.firstwave.com.au has no MX records.
Question and response
Question
dig ns1.firstwave.com.au. MX
Answer
The response has no answer records.
Authority
firstwave.com.au. 300 SOA ns1.firstwave.com.au. admin.firstwave.com.au. 2018035001 3600 600 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0