smtp.free.fr has no NS records.
NS records for this zone are defined at free.fr.
NS records for this zone are defined at free.fr.
Question and response
Question
dig smtp.free.fr. NS
Answer
The response has no answer records.
Authority
free.fr. 86400 SOA freens1-g20.free.fr. hostmaster.proxad.net. 2026031423 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0