rdir.inxmail.com has no CNAME records.
Question and response
Question
dig rdir.inxmail.com. NS
Answer
The response has no answer records.
Authority
inxmail.com. 3263 SOA ns1.dmz.inxmail.de. hostmaster.inxmail.de. 2025120801 3600 1200 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0