ns2.csgsystems.com has no MX records.
Question and response
Question
dig ns2.csgsystems.com. MX
Answer
The response has no answer records.
Authority
csgsystems.com. 900 SOA ns1.csgsystems.com. postmaster.csgsystems.com. 2014021664 900 600 1209600 900
Additional
. 0 OPT ; payload 4000, xrcode 0, version 0, flags 0