network.k.io has no MX records.
Question and response
Question
dig network.k.io. MX
Answer
The response has no answer records.
Authority
network.k.io. 3600 SOA ns1.katapult.io. dns-admin.katapult.io. 1763588835 28800 7200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0