Is INBOX special in a Maildir?

[Julien Cubizolles]

I'm using OfflineIMAP to sync a remote IMAP account to a local Maildir,
and dovecot to access it from Gnus using a nnimap method, like many
do. The Maildir uses the fs layout (/ for separators) and has folders like:

INBOX
INBOX/cur
INBOX/new
INBOX/tmp

General
General/cur
General/new
General/tmp

but also like:

cur
new
tmp

The General folder can be accessed but Gnus always report no messages in
the group it calls INBOX, even though the folder named INBOX contains
some messages

I suspect it has to do with Gnus being confused about what INBOX really
is: either the root of the Maildir, or the folder actually named
INBOX. Do I need to change something in my offlineimap setup, or in
Gnus' ?

Julien.