mailspool.core.kcom.com has no CNAME records.
Question and response
Question
dig mailspool.core.kcom.com. NS
Answer
The response has no answer records.
Authority
core.kcom.com. 10626 SOA ibex.kcom.com. hostmaster.kcom.com. 2013062501 28800 7200 604800 28800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0