ns2.netnames.net has no MX records.
Question and response
Question
dig ns2.netnames.net. MX
Answer
The response has no answer records.
Authority
netnames.net. 172800 SOA udns1.cscdns.net. hostmaster.cscdns.net. 2017101447 3600 1800 3600000 172800
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0