_spf.travelclick.com has no NS records.
NS records for this zone are defined at travelclick.com.
NS records for this zone are defined at travelclick.com.
Question and response
Question
dig _spf.travelclick.com. NS
Answer
The response has no answer records.
Authority
travelclick.com. 3600 SOA a2-66.akam.net. hostmaster.travelclick.com. 2018082959 10800 600 604800 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0