smtp.directi.com has no NS records.
NS records for this zone are defined at directi.com.
NS records for this zone are defined at directi.com.
Question and response
Question
dig smtp.sendgrid.net. NS
Answer
The response has no answer records.
Authority
sendgrid.net. 180 SOA ns10.dnsmadeeasy.com. dns.dnsmadeeasy.com. 2011294283 14400 600 1728000 180
Additional
. 0 OPT ; payload 1280, xrcode 0, version 0, flags 0