mx400.echelon.nu has no MX records.
Question and response
Question
dig mx400.echelon.nu. MX
Answer
The response has no answer records.
Authority
echelon.nu. 3600 SOA ns.echelon.nl. hostmaster.echelon.nu. 2025040902 14400 3600 604800 3600
Additional
. 0 OPT ; payload 1680, xrcode 0, version 0, flags 0