mailrelay.ngdc.net has no MX records.
Question and response
Question
dig mailrelay.ngdc.net. MX
Answer
The response has no answer records.
Authority
ngdc.net. 600 SOA authns1.ngdc.net. hostmaster.ngdc.net. 2025061301 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0