mx.movistar.es has no NS records.
NS records for this zone are defined at movistar.es.
NS records for this zone are defined at movistar.es.
Question and response
Question
dig mx.movistar.es. NS
Answer
The response has no answer records.
Authority
movistar.es. 3600 SOA dns1.movistar.es. admondns.tsm.es. 2017073423 28800 3600 2592000 3600
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0