pop.achcity.com has no CNAME records.
Question and response
Question
dig pop.achcity.com. NS
Answer
The response has no answer records.
Authority
achcity.com. 3298 SOA achcity.com. noc.achmail.ru. 2026012823 10800 3600 604800 86400
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0