mail1.iecc.com has no CNAME records.
Question and response
Question
dig mail1.iecc.com. NS
Answer
The response has no answer records.
Authority
iecc.com. 3106 SOA sdn.iecc.com. dnsmaster.iecc.com. 2026022701 10800 900 604800 7200
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0