go
mail.oka-3.com, mail.boinbb.com and 122x216x85x58.ap122.ftth.ucom.ne.jp point to 122.216.85.58.

122x216x85x58.ap122.ftth.ucom.ne.jp
a records
 
+ 122.216.85.58 122.216.0.0/14 AS17506 -
+ --- -

mail.boinbb.com
a records
 
+ 122.216.85.58 122.216.0.0/14 AS17506 122x216x85x58.ap122.ftth.ucom.ne.jp
+ --- 122x216x85x58.ap122.ftth.ucom.ne.jp

mail.oka-3.com
a records
 
+ 122.216.85.58 122.216.0.0/14 AS17506 122x216x85x58.ap122.ftth.ucom.ne.jp
+ --- 122x216x85x58.ap122.ftth.ucom.ne.jp
ip numbers of host
122.216.85.58
ptrs of ip numbers
122x216x85x58.ap122.ftth.ucom.ne.jp
hostnames sharing ip with a-records
122x216x85x58.ap122.ftth.ucom.ne.jp
mail.boinbb.com
mail.oka-3.com
domains using this as mailserver
boinbb.com
oka-3.com