exchange.ecomputer.es has no CNAME records.
Question and response
Question
dig exchange.ecomputer.es. NS
Answer
The response has no answer records.
Authority
ecomputer.es. 10800 SOA dns7.servidoresdns.net. hostmaster.servidoresdns.net. 2002052964 21600 3600 2419200 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0