email.codestack.org has no CNAME records.
Question and response
Question
dig email.codestack.org. NS
Answer
The response has no answer records.
Authority
codestack.org. 683 SOA ns-1479.awsdns-56.org. awsdns-hostmaster.amazon.com. 1 7200 900 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0