helium.ns.hetzner.de has no MX records.
Question and response
Question
dig helium.ns.hetzner.de. MX
Answer
The response has no answer records.
Authority
hetzner.de. 3600 SOA ns1.your-server.de. postmaster.your-server.de. 2026020311 86400 1800 3600000 3600
Additional
. 0 OPT ; payload 4096, xrcode 0, version 0, flags 0