brsmtp.orange.pl has no CNAME records.
Question and response
Question
dig brsmtp.orange.pl. NS
Answer
The response has no answer records.
Authority
orange.pl. 10800 SOA ns1.corpnet.pl. dns-pl.orange.com. 2026030201 172800 21600 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0