mx.host.bg has no CNAME records.
Question and response
Question
dig mx.host.bg. NS
Answer
The response has no answer records.
Authority
host.bg. 66 SOA pns1.host.bg. hostmaster.superhosting.bg. 2026022408 14400 1800 2419200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0