Courier IMAP, unlike some other IMAP servers, uses
the period (.) as its hierarchy delimiter. When you
do the command:
a002 list "" "INBOX"
Courier IMAP responds with the following:
* LIST (\Marked \HasChildren) "." "INBOX"
(Of course, the name attributes may be different
depending on the situation.) The hierarchy delimiter
is clearly indicated there, as required by the RFC.
However, Althea proceeds to assume that the forward
slash (/) is the hierarchy delimiter:
a002 list "" "INBOX/*"
And so of course Courier replies immediately with:
a002 OK LIST completed.
So, the subfolders do not get shown. Please make the
changes required to respond to the hierarchy
delimiter as indicated in the LIST response.