mx.sferamail.pro has no CNAME records.
Question and response
Question
dig mx.sferamail.pro. NS
Answer
The response has no answer records.
Authority
sferamail.pro. 10800 SOA dns.sfera.net. hostmaster.server.sfera.net. 2023031653 86400 14400 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0