mail.webcas.net has no CNAME records.
Question and response
Question
dig mail.webcas.net. NS
Answer
The response has no answer records.
Authority
webcas.net. 3600 SOA dns.webcas.net. nfujita.azia.co.jp. 2026022502 3600 1800 86400 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0