ns3.blue.net has no MX records.
Question and response
Question
dig ns3.blue.net. MX
Answer
The response has no answer records.
Authority
blue.net. 3600 SOA ns1.blue.net. adminblue.blue.net. 520800008 1200 180 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0