mail.avala.bg has no CNAME records.
Question and response
Question
dig mail.avala.bg. NS
Answer
The response has no answer records.
Authority
avala.bg. 10800 SOA lada.avala.bg. root.mail.avala.bg. 2025040376 28800 7200 2400000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0