ns3.sdu.dk has no MX records.
Question and response
Question
dig ns3.sdu.dk. MX
Answer
The response has no answer records.
Authority
sdu.dk. 900 SOA ns1.sdu.dk. dns.sdu.dk. 2012272506 86400 7200 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0