_spf.ewmail.com has no NS records.
NS records for this zone are defined at ewmail.com.
NS records for this zone are defined at ewmail.com.
Question and response
Question
dig _spf.ewmail.com. NS
Answer
The response has no answer records.
Authority
ewmail.com. 3600 SOA dns1.ewdns.ch. hostmaster.everyware.ch. 1765298845 10800 3600 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0