mail.adhost.com has no CNAME records.
Question and response
Question
dig mail.adhost.com. NS
Answer
The response has no answer records.
Authority
adhost.com. 10744 SOA ns1.ral.hostedsolutions.com. hostmaster.hostedsolutions.com. 2018091372 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0