_netblocks1.demandware.net has no CNAME records.
Question and response
Question
dig _netblocks1.demandware.net. NS
Answer
The response has no answer records.
Authority
demandware.net. 51 SOA dns01.salesforce.com. hostmaster.salesforce.com. 2014748989 600 900 2592000 60
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0