smtp1.comclark.com has no CNAME records.
Question and response
Question
dig smtp1.comclark.com. NS
Answer
The response has no answer records.
Authority
comclark.com. 770 SOA ns1.comclark.com. hostmaster.comclark.com. 2013061202 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0