pop.nctc.com has no MX records.
Question and response
Question
dig pop.nctc.com. MX
Answer
The response has no answer records.
Authority
nctc.com. 600 SOA ns1.blue.net. adminblue.blue.net. 520826382 1200 180 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0