mta2.mastercard-email.com has no CNAME records.
Question and response
Question
dig mta2.mastercard-email.com. NS
Answer
The response has no answer records.
Authority
mastercard-email.com. 277 SOA dns1.mastercard.com. hostmaster.mastercard.com. 2011072602 14400 3600 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0