imap.ctl.one has no CNAME records.
Question and response
Question
dig imap.ctl.one. NS
Answer
The response has no answer records.
Authority
ctl.one. 300 SOA ns3.level3.net. postmaster.ns3.level3.net. 2026020400 300 240 86400 300
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0