nsdo.deterlab.net has no MX records.
Question and response
Question
dig nsdo.deterlab.net. MX
Answer
The response has no answer records.
Authority
deterlab.net. 3600 SOA nsdo.deterlab.net. root.deterlab.net. 2512241242 10800 7200 28800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0