mail.free.org has no CNAME records.
Question and response
Question
dig mail.free.org. NS
Answer
The response has no answer records.
Authority
free.org. 2827 SOA ns0.free.org. hostmaster.free.org. 2026022001 28800 3600 691200 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0