gdn has no MX records.
Question and response
Question
dig gdn. MX
Answer
The response has no answer records.
Authority
gdn. 900 SOA ns1.nic.gdn.gdn. postmaster.nic.gdn. 1501647330 21600 1800 2419200 900
Additional
. 0 OPT ; payload 1400, xrcode 0, version 0, flags 0