spf.zml0.com has no NS records.
NS records for this zone are defined at zml0.com.
NS records for this zone are defined at zml0.com.
Question and response
Question
dig spf.zml0.com. NS
Answer
The response has no answer records.
Authority
zml0.com. 300 SOA a2-66.akam.net. hostmaster.zdirect.com. 2016061114 3600 1800 172800 300
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0