spf01.yahoo.co.jp has no NS records.
NS records for this zone are defined at yahoo.co.jp.
NS records for this zone are defined at yahoo.co.jp.
Question and response
Question
dig spf01.yahoo.co.jp. NS
Answer
The response has no answer records.
Authority
yahoo.co.jp. 900 SOA yahoo.co.jp. postmaster.yahoo.co.jp. 2603130012 1800 900 86400 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0