u2368638.wl139.sendgrid.net has no NS records.
NS records for this zone are defined at wl139.sendgrid.net.
NS records for this zone are defined at wl139.sendgrid.net.
Question and response
Question
dig u2368638.wl139.sendgrid.net. NS
Answer
The response has no answer records.
Authority
wl139.sendgrid.net. 1800 SOA aisha.ns.cloudflare.com. dns.cloudflare.com. 2399487646 10000 2400 604800 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0