ip.flexfonenet.dk has no MX records.
Question and response
Question
dig ip.flexfonenet.dk. MX
Answer
The response has no answer records.
Authority
ip.flexfonenet.dk. 86400 SOA auth01.dns.sippeer.dk. hostmaster.flexfone.dk. 2016111101 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0