pmx01.mail.LF.net has no CNAME records.
Question and response
Question
dig pmx01.mail.LF.net. NS
Answer
The response has no answer records.
Authority
lf.net. 3573 SOA dns1.lf.net. hostmaster.lf.net. 2026030600 86400 10800 604800 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0