prod-mail.geant.net has no MX records.
Question and response
Question
dig prod-mail.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 1232, xrcode 0, version 0, flags 0