I am new to zimbra and want to know a couple steps to be done in setting up my mail server.

I have configured 3 domains in zcs 8.02. In the 3 domain 2 will have internal access and external world access. The third domain is only for internal mail communication (only between the 3 domains).

1. I want to know to how i should configure the 3rd domain such that it is only used for internal communication.
2. In all the 3 domains (separately) i want to group users by their job profile and assign different quota settings. Is this possible? Even webmail should be blocked for some set of users.
3. The domain which is used for internal communication should not have access to webmail rather it will be accessed only using outlook or other mail client.

Can someone help on the above queries. Thanks in advance.