spf.guardedhost.com has no NS records.
NS records for this zone are defined at guardedhost.com.
NS records for this zone are defined at guardedhost.com.
Question and response
Question
dig spf.guardedhost.com. NS
Answer
The response has no answer records.
Authority
guardedhost.com. 900 SOA primary.guardeddns.net. dns-admin.guardeddns.net. 347 28800 450 1209600 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0