smtp-jds55.internetx.com has no CNAME records.
Question and response
Question
dig smtp-jds55.internetx.com. NS
Answer
The response has no answer records.
Authority
internetx.com. 1629 SOA nsa.domain-robot.org. domain-support.internetx.de. 2026022501 43200 7200 1209600 432000
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0