rel11.migadu.com has no CNAME records.
Question and response
Question
dig rel11.migadu.com. NS
Answer
The response has no answer records.
Authority
migadu.com. 311 SOA ns0.migadu.com. hostmaster.migadu.com. 1772818053 1200 900 1209600 3600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0