web1v1.mail.ziggo.com has no CNAME records.
Question and response
Question
dig web1v1.mail.ziggo.com. NS
Answer
The response has no answer records.
Authority
mail.ziggo.com. 171 SOA ns1.flowmailer.net. contact.flowmailer.net. 2026021602 86400 7200 7200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0