mx01.perfora.net has no CNAME records.
Question and response
Question
dig mx01.perfora.net. NS
Answer
The response has no answer records.
Authority
perfora.net. 381 SOA rns.ui-dns.de. dnsadmin.1und1.de. 2013099627 10800 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0