==== Required information ====
- iRedMail version: 0.8.5
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: Ubuntu Server alternate 12.04 lts
- Related log if you're reporting an issue:
====

Hello Mr Zhang, hello everyone

As in the description, iRedMail is installed on Ubuntu and i configured the machine to provide a DNS, and tested it on a local network so when i type www.mail.tiyebhost.mr i get the mail interface (roundcube), DNS configuration for Ubuntu is correct i' m sure.
But i have another DNS server which is connected to the router (where i connect to the Internet), this one is Windows Server 2003, i connected this server with my Ubuntu and after days of troubles, i finally succeeded in the following operations:

1-)From Windows i could see the dns configuration of Ubuntu so i could access mail interface by typing www.mail.tiyebhost.mr on my browser.
2-)I was able to ping google.com or much more than that i could connect my Ubuntu to the internet only through the interface with Windows server .
3-)I configured Forwards, or what they called (Split DNS + SMTP + NAT), on Windows Server so i receive emails sent to my iRedMail account from my account in google and other mail services and visa versa!!, which was the greatest achievement for me till now.
The last thing i really need to be able to, is how to access my mail interface on Ubuntu from the internet, while i have an active Zone 'tiyebhost.mr' on Windows with a public ip address 151.#.#.#, i want to mention that Ubuntu has only a local ip 192.168.#.# i dont know where it get that.
Is it enough for me to access roundcube interface to be able to send and receive emails without some mail protocols?,i mean even if i opened roundcube, how could it understand that i'm actually sending and receiving an email, and how  it is going to work?.
i have a lot of questions but enough for now, i appreciate any help. 
Thank you in advance.