mail3.primerelay.net has no CNAME records.
Question and response
Question
dig mail3.primerelay.net. NS
Answer
The response has no answer records.
Authority
primerelay.net. 75 SOA ns1.primerelay.net. hostmaster.primerelay.net. 2024102401 15800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0