Here is what I am trying to setup with ZCS : I would like Zimbra web UI (installed on zimbra.example.com server) to access external mailboxes located on remote Postfix server(s) (let's call it remote.example.com).
To test the solution, I have created a user and I attached him an external account. All is right : the external account has it's own folder, it can get e-mail from IMAP mailbox on remote.example.com and it can send e-mail via that server (added zimbra.example.com IP in remote Postfix "mynetworks").
The problem : it seems that Zimbra external account can only "read" the distant IMAP mailbox. When I save a draft of send an e-mail, it is never written into the IMAP server, only as Zimbra local data.
So, please, is it possible for Zimbra to act as a standard client with remote IMAP mailboxes ? Like Thunderbird for example.
I saw that post giving a negative answer : "Is that possible to use Zimbras only as an IMAP client of an external MTA?"
But what I do not understand is why Zimbra seems to be able only to check IMAP with my setup. Is it a real limitation of the product ?