srv2.spambusters.email has no CNAME records.
Question and response
Question
dig srv2.spambusters.email. NS
Answer
The response has no answer records.
Authority
spambusters.email. 10800 SOA ns1.webhs.org. reports.webhs.pt. 2025120800 86400 7200 3600000 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0