_spf-cust.clickmeeting.com has no CNAME records.
Question and response
Question
dig _spf-cust.clickmeeting.com. NS
Answer
The response has no answer records.
Authority
clickmeeting.com. 158 SOA ns11.constellix.com. dns.constellix.com. 2015011122 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0