mail.prosoft.bg has no CNAME records.
Question and response
Question
dig mail.prosoft.bg. NS
Answer
The response has no answer records.
Authority
prosoft.bg. 1793 SOA ns.datalink.bg. admin.datalink.bg. 2002101119 900 600 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0