dns7.aena.es has no MX records.
Question and response
Question
dig dns7.aena.es. MX
Answer
The response has no answer records.
Authority
aena.es. 900 SOA dns6.aena.es. please_set_email.absolutely.nowhere. 857 10800 3600 2592000 900
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0