mx.travelling-to.com has no NS records.
NS records for this zone are defined at travelling-to.com.
NS records for this zone are defined at travelling-to.com.
Question and response
Question
dig mx.travelling-to.com. NS
Answer
The response has no answer records.
Authority
travelling-to.com. 3600 SOA dns.travelling-to.com. hostmaster.travelling-to.com. 1446048456 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0