go
smtp.efcmailserver.com point to 72.21.41.122.

smtp.efcmailserver.com
cname records
efcmailserver.com
+ 72.21.41.122 72.21.32.0/19 AS22576 -
+ --- -

efcmailserver.com
ptr records
 
+ 72.21.41.122 72.21.32.0/19 AS22576 -
+ --- -
ip numbers of host
72.21.41.122
ptrs of ip numbers
efcmailserver.com
hostnames sharing ip with a-records
smtp.efcmailserver.com
domains using this as mailserver
efcmailserver.com