mail.ec21hosting.com has no CNAME records.
Question and response
Question
dig mail.ec21hosting.com. NS
Answer
The response has no answer records.
Authority
ec21hosting.com. 3457 SOA ns1.namesvr.net. root.ec21hosting.com. 2010080617 3600 300 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0