mx1.codetel.mail2world.com has no CNAME records.
Question and response
Question
dig mx1.codetel.mail2world.com. NS
Answer
The response has no answer records.
Authority
mail2world.com. 110 SOA mwdns10vmoc.mail2world.com. dns_admin.mail2world.net. 2016043392 3600 300 1814400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0