mail.managedns.org has no CNAME records.
Question and response
Question
dig mail.managedns.org. NS
Answer
The response has no answer records.
Authority
managedns.org. 3564 SOA dns16.managedns.org. hostmaster.managedns.org. 2014015042 3600 600 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0