ns.casscomm.com has no MX records.
Question and response
Question
dig ns.casscomm.com. MX
Answer
The response has no answer records.
Authority
casscomm.com. 600 SOA ns.casscomm.com. postmaster.ns.casscomm.com. 2008041129 90 30 259200 600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0