ns2.ns-serve.net has no MX records.
Question and response
Question
dig ns2.ns-serve.net. MX
Answer
The response has no answer records.
Authority
ns-serve.net. 86400 SOA ns1.ns-serve.net. root.ns1.ns-serve.net. 1711365600 10800 3600 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0