28nbcopv01.telefonicaonline.com has no MX records.
Question and response
Question
dig 28nbcopv01.telefonicaonline.com. MX
Answer
The response has no answer records.
Authority
telefonicaonline.com. 900 SOA dns1.movistar.es. dnsadmin.tsai.es. 45 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0