mail.xlhost.com has no CNAME records.
Question and response
Question
dig mail.xlhost.com. NS
Answer
The response has no answer records.
Authority
xlhost.com. 4769 SOA dns4.ee.net. hostmaster.ee.net. 2017030854 28800 7200 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0