mx.rugbymags.com has no NS records.
NS records for this zone are defined at rugbymags.com.
NS records for this zone are defined at rugbymags.com.
Question and response
Question
dig mx.rugbymags.com. NS
Answer
The response has no answer records.
Authority
rugbymags.com. 3600 SOA dns.rugbymags.com. hostmaster.rugbymags.com. 1780772757 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0