mail.tsai.es has no MX records.
Question and response
Question
dig tsaidmz.tsai.es. MX
Answer
The response has no answer records.
Authority
tsai.es. 300 SOA nsjc8hos01.telefonica-data.com. dnsadmin.tsai.es. 2013050834 86400 7200 2592000 300
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0