mailer1.ezyield.com has no CNAME records.
Question and response
Question
dig mailer1.ezyield.com. NS
Answer
The response has no answer records.
Authority
ezyield.com. 7200 SOA a2-66.akam.net. hostmaster.ezyield.com. 2015111227 10800 600 604800 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0