mail.mexline.com has no CNAME records.
Question and response
Question
dig mail.mexline.com. NS
Answer
The response has no answer records.
Authority
mexline.com. 600 SOA ns02.mexline.com. netmin.mexline.com. 2026022702 3600 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0