_spf.rackanddata.com has no NS records.
NS records for this zone are defined at rackanddata.com.
NS records for this zone are defined at rackanddata.com.
Question and response
Question
dig _spf.rackanddata.com. NS
Answer
The response has no answer records.
Authority
rackanddata.com. 38400 SOA authns1.rackanddata.com. domainadmin.rackanddata.com. 1375326455 10800 3600 604800 38400
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0