mx.e.movistar.es has no CNAME records.
Question and response
Question
dig mx.e.movistar.es. NS
Answer
The response has no answer records.
Authority
e.movistar.es. 4821 SOA ns12.acens.net. nsadmin.dns-servicios.es. 2025865625 14400 7200 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0