_spf.x7z.ru has no NS records.
NS records for this zone are defined at x7z.ru.
NS records for this zone are defined at x7z.ru.
Question and response
Question
dig _spf.x7z.ru. NS
Answer
The response has no answer records.
Authority
x7z.ru. 300 SOA ns1.timeweb.ru. dns.timeweb.ru. 1042517 28800 7200 259200 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0