mx.swisswordl.com has no NS records.
NS records for this zone are defined at swisswordl.com.
NS records for this zone are defined at swisswordl.com.
Question and response
Question
dig mx.swisswordl.com. NS
Answer
The response has no answer records.
Authority
swisswordl.com. 3600 SOA dns.swisswordl.com. hostmaster.swisswordl.com. 1541593960 43200 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0