Folders not visible via IMAP, when connecting to other mailbox

Hi,

I'm experiencing a problem when connecting via IMAP to a newly installed Exchange 2013 server.
We have an application that will monitor a specific folder within a users' mailbox via IMAP, and pick up mails within it.

When I test the IMAP connection with the credentials of the user itself, I can see all folders.
When I connect via an account that accesses the mailbox via IMAP (and which has full mailbox access on the mbx), I don't see certain folders.

Actually any new folder I create isn't visible when queried via IMAP with another user.

I've already updated the folderlist, queried IMAP folders, and disabled "when displaying hierarchy in outlook, show only subscribed folders", but they just don't show up.

Any ideas?
PS : We're using Outlook 2010