postbox-300.xqueue.com has no CNAME records.
Question and response
Question
dig postbox-300.xqueue.com. NS
Answer
The response has no answer records.
Authority
xqueue.com. 900 SOA ns0.isprit2.de. hostmaster.xq11.com. 2025101900 28800 1800 691200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0