How to configure IMP to see folders of Courier-IMAP?

[Stephane Bortzmeyer]

My IMAP server is Courier 1.4.0. My Webmail is IMP 2.2.6. Users only
see the INBOX folder and they never see the other folders which mutt,
for instance, can display.

I noticed this in the IMP FAQ:

http://www.horde.org/faq/admin/trouble/index.php#t25
"In IMP, users can't use any folders besides INBOX."

It tells to change the $default->folders but what should I put for
Courier? I tried "Maildir/" and "INBOX/" without improvment.