pop.dreamhost.com has no CNAME records.
Question and response
Question
dig pop.dreamhost.com. NS
Answer
The response has no answer records.
Authority
dreamhost.com. 300 SOA ns1.dreamhost.com. hostmaster.dreamhost.com. 2026030401 1798 1800 1209600 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0