nsd.scaleway.com has no MX records.
Question and response
Question
dig nsd.scaleway.com. MX
Answer
The response has no answer records.
Authority
scaleway.com. 3600 SOA nsa.scaleway.com. hostmaster.scaleway.com. 2026021901 3600 300 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0