I am using ubuntu operating system
and installed zimbra mail server and
domain name server - bind 9 in ubuntu.

The installation of zimbra mail server is completed
and made an entry in DNS for mail server for
redirecting mail entries to that system.

In Forward zone :

ityug.com. IN MX vidyayug.ityug.com
vidyayug IN A

In Reverse Zone :

10 IN PTR vidyayug.ityug.com.

when i send mail to gmail or yahoo mail
the mail which i was sending is going to
spam instead of inbox.

And I am using Static IP address.

My doubt is :

In my DNS I didn't map with any public ip address ?

How can I map with public address ?

After configuring internal DNS did i need to map with any other things ?