smtp.spf.ziggo.nl has no CNAME records.
Question and response
Question
dig smtp.spf.ziggo.nl. NS
Answer
The response has no answer records.
Authority
ziggo.nl. 10800 SOA ns1.upc.biz. digitaldomainoffice.vodafoneziggo.com. 2026022601 14400 3600 2419200 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0