because of some complicated issue, I decide use freedns.centos-webpanel.com to manage my dns.
as I know and used bind9, you can create in-addr.arpa files to handle reverse zone and avoid spam for mail server. but in freedns of cwp there is no item for that.
used this but not answered in result of dig -x:
@ PTR example.com
I'm afraid of making my own dns server because of ddos and dns attacks. what's best free solution?