smtp.acens.com has no CNAME records.
Question and response
Question
dig smtp.acens.com. NS
Answer
The response has no answer records.
Authority
acens.com. 3600 SOA ns1.acens.net. hostmaster.ns1.acens.net. 1772270685 14400 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0