exchange3.brunico.com has no CNAME records.
Question and response
Question
dig exchange3.brunico.com. NS
Answer
The response has no answer records.
Authority
brunico.com. 300 SOA ns-1562.awsdns-03.co.uk. awsdns-hostmaster.amazon.com. 1382477856 43200 10800 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0