u3381634.wl135.sendgrid.net has no NS records.
NS records for this zone are defined at wl135.sendgrid.net.
NS records for this zone are defined at wl135.sendgrid.net.
Question and response
Question
dig u3381634.wl135.sendgrid.net. NS
Answer
The response has no answer records.
Authority
wl135.sendgrid.net. 1800 SOA aisha.ns.cloudflare.com. dns.cloudflare.com. 2399315158 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0