courier.fuse.net has no CNAME records.
Question and response
Question
dig courier.fuse.net. NS
Answer
The response has no answer records.
Authority
fuse.net. 687 SOA ns1.fuse.net. hostmaster.fuse.net. 3661 10800 3600 2419200 900
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0