ns3.apnic.net has no MX records.
Question and response
Question
dig ns3.apnic.net. MX
Answer
The response has no answer records.
Authority
apnic.net. 3600 SOA ns.apnic.net. dns-ops.apnic.net. 2020123479 3600 1800 691200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0