mx.movistar.es has no CNAME records.
Question and response
Question
dig mx.movistar.es. NS
Answer
The response has no answer records.
Authority
movistar.es. 2266 SOA dns1.movistar.es. admondns.tsm.es. 2017073423 28800 3600 2592000 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0