_netblocks.accellion.com has no CNAME records.
Question and response
Question
dig _netblocks.accellion.com. NS
Answer
The response has no answer records.
Authority
accellion.com. 49 SOA dnsma.accellion.com. root.mail.accellion.com. 2025092500 28800 7200 604800 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0