mailb.FPC.ru has no CNAME records.
Question and response
Question
dig mailb.FPC.ru. NS
Answer
The response has no answer records.
Authority
FPC.ru. 364 SOA ns3-l2.nic.ru. ast.resourceservice.ru. 65012932 14400 3600 604800 600
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0