ns01.geant.net has no MX records.
Question and response
Question
dig ns01.geant.net. MX
Answer
The response has no answer records.
Authority
geant.net. 900 SOA grid01.geant.net. hostmaster.dante.net. 2015081010 3600 7200 2419200 900
Additional
. 0 OPT ; payload 1220, xrcode 0, version 0, flags 0