mx.phpnet.org has no CNAME records.
Question and response
Question
dig mx.phpnet.org. NS
Answer
The response has no answer records.
Authority
phpnet.org. 1670 SOA ns.phpnet.org. grenoble.phpnet.org. 2026022633 3600 1800 1209600 1800
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0