mailrelay.gcos.dk has no MX records.
Question and response
Question
dig mailrelay.gcos.dk. MX
Answer
The response has no answer records.
Authority
gcos.dk. 3600 SOA name1.t26.dk. support.globalconnect.dk. 2017060918 14400 3600 3628800 3600
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0