[Dovecot] Migration problems from Courier-Imap

[Mattia Martinello]

Hi,
I'm migrating from Courier-Imap to Dovecot-Imapd and I have some problems..
I don't want to change the IMAP folders, so I wish to have Dovecot's 
compatibility with Courier's IMAP folders.
In the Dovecot configuration I configured this:

namespace private {
 separator = .
 prefix = INBOX.
 inbox = yes
}

Dovecot correctly shows me the INBOX folder, but doesn't show me the 
subfolders anymore...

What can I do to solve this problem?

Thank you very much and goodbye.
Mattia.