core.noris.net has no MX records.
Question and response
Question
dig core.noris.net. MX
Answer
The response has no answer records.
Authority
core.noris.net. 600 SOA dns0.noris.net. hostmaster.noris.net.core.noris.net. 4269 86400 86400 2419200 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0