28sbne06.telefonicaonline.com has no MX records.
Question and response
Question
dig 28sbne06.telefonicaonline.com. MX
Answer
The response has no answer records.
Authority
telefonicaonline.com. 900 SOA dns2.movistar.es. dnsadmin.tsai.es. 45 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0