I'm new with Zimbra and after a long search, I can't find the answer to my question.
For now I use a paid version of OpenXchange.
When I create a user on OpenXchange, I give him the address of the server (IMAP or POP) and SMTP server address.
OpenXchange make an "interface" between Exchange Features and the storage of emails.
Emails comming the on mail infrastructure, and Dovecot store the user messages.
I would like to keep messages hosted on my mail server and Zimbra works like OpenXchange, in fact it goes real-time view messages via IMAP.
I do not find in the documentation if it's possible to do this for the main account.
I see just that one account can have an external address in IMAP...