Here is my set up and I have no clue how to proceed further since I am running out of ideas. My mail gateway is pointed to different linux server where only postfix is running say having hostname mailgw.example.com and mailbox server is actually a Zimbra server 7.1 where all the user mailboxes reside.
Above that I set up a split-dns server using dnsmasq on Mailbox server itself and would like to know what other settings I need to configure in DNS or in Zimbra installation to make the installation successful.
INTERNET----->MailGW [Linux Postfix]-------> MailBox [zimbra 7.1]
Just FYi, all my servers are behind firewall hence I had to set up split-dns server