smtp4.conecta.orange.es has no MX records.
Question and response
Question
dig smtp4.conecta.orange.es. MX
Answer
The response has no answer records.
Authority
orange.es. 3600 SOA dns4.wanadoo.es. dominios.orange.es. 35186 3600 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0