mail.pro-linuxpl.com has no CNAME records.
Question and response
Question
dig mail.pro-linuxpl.com. NS
Answer
The response has no answer records.
Authority
pro-linuxpl.com. 217 SOA dns10.linuxpl.com. hostmaster.pro-linuxpl.com. 2024121701 300 3600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0