mail01.smhost.pro has no CNAME records.
Question and response
Question
dig mail01.smhost.pro. NS
Answer
The response has no answer records.
Authority
smhost.pro. 10800 SOA ns1.smhost.pro. rtrojan.supermedia.pl. 2026022102 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0