mx.ptd.net has no CNAME records.
Question and response
Question
dig mx.ptd.net. NS
Answer
The response has no answer records.
Authority
ptd.net. 2512 SOA dns1.ptd.net. etoybrg.corp.ptd.net. 2025062501 10800 3600 604800 10800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0