mail.tanhost.com has no CNAME records.
Question and response
Question
dig mail.tanhost.com. NS
Answer
The response has no answer records.
Authority
tanhost.com. 1097 SOA ns1.tanhost.com. admin.support.tanhost.com. 2025111804 86400 7200 3600000 1440
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0