mx2.mail.bg has no NS records.
NS records for this zone are defined at mail.bg.
NS records for this zone are defined at mail.bg.
Question and response
Question
dig mx2.mail.bg. NS
Answer
The response has no answer records.
Authority
mail.bg. 86400 SOA ns.mail.bg. webmaster.mail.bg. 2023072677 28800 7200 1209600 86400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0