smtp.cableworld.es has no MX records.
Question and response
Question
dig smtp.cableworld.es. MX
Answer
The response has no answer records.
Authority
cableworld.es. 3600 SOA dns. hostmaster.cableworld.es. 2025093001 10800 3600 604800 38400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0