_spf.adp.com has no NS records.
NS records for this zone are defined at adp.com.
NS records for this zone are defined at adp.com.
Question and response
Question
dig _spf.adp.com. NS
Answer
The response has no answer records.
Authority
adp.com. 60 SOA dc01exdnsgm.net.adp.com. hostmaster.adp.com. 2015071397 10800 3600 2592000 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0