mta-2d5b2c00.ip4.emsmtp.com has no CNAME records.
Question and response
Question
dig mta-2d5b2c00.ip4.emsmtp.com. NS
Answer
The response has no answer records.
Authority
emsmtp.com. 180 SOA ns10.digicertdns.com. dns.digicertdns.com. 2009010389 43200 3600 1209600 180
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0