[SM-USERS] Collapsable Folders broken with Dovecot IMAP server

[Ole H. N. <Ole...@fy...>]

We have installed RedHat's RPM package squirrelmail-1.4.8-5.el5_4.10
on a RedHat RHEL 5.5 server.  Squirrelmail connects to our mailbox server
which also runs RHEL 5.5 and the dovecot-1.0.7-7.el5 IMAP server RPM package.
The Dovecot IMAP server uses Sendmail as MTA and mailboxes in mbox format.

Squirrelmail seems to be working fine, except for the collapsible subfolders.
The user has enabled Options - Folder Preferences "Enable Collapsable Folders: 
  Yes".  However, in the left-hand Folders panel the subdirectories themselves
are not shown at all (these are real filesystem subdirectories, not folders with
subfolders).

All of the subfolders in the subdirectories appear as one very long list of
folders, and there are no + or - signs allowing to collapse the subfolders
(actually, there are a handful of subdirectories which do in fact have + or -
next to the first folder in the subdirectory).  The subdirectories are indented
about 2 characters, so Squirrelmail seems to realize that they are subfolders.

Our Squirrelmail config has been set to $imap_server_type='dovecot', but still
it seems that Squirrelmail doesn't handle filesystem subdirectories on the
Dovecot server correctly.  From my reading the documentation and the Changelog
there doesn't appear to be any documented feature in Squirrelmail which corrects
this broken behavior.

The same issue was reported on this list on November 5, 2008:
http://sourceforge.net/mailarchive/forum.php?thread_name=20353125.post%40talk.nabble.com&forum_name=squirrelmail-users

Questions:
1. Does anyone know of a Squirrelmail config that fixes Collapsable Folders with
    a Dovecot IMAP server ?
2. Is this really a bug in Squirrelmail, and how can it be fixed ?

The Needed Details of our installation:

# SquirrelMail version: RedHat's squirrelmail-1.4.8-5.el5_4.10
# Every plugin installed: None
# PHP version: RedHat's php-5.1.6-27.el5
# Web server: RedHat's Apache httpd-2.2.3-43.el5
# IMAP server: RedHat's dovecot-1.0.7-7.el5
# SMTP server: RedHat's sendmail-8.13.8-8.el5
# OS: RedHat RHEL 5.5 with all updates.
# How your software was installed: RedHat's RPM package
# Browsers tried: Firefox 3.6.4 on Linux, Internet Explorer 8.0
# Any things that might make your install different: Not that I know of,
   except that we use https:
# Error Messages: In the Apache error log (probably not relevant):

PHP Notice:  Undefined variable: charset_converted in 
/usr/share/squirrelmail/functions/mime.php on line 316, referer: 
https://xxx.fysik.dtu.dk/src/right_main.php
[Mon Jul 19 13:43:01 2010] [error] [client 130.225.86.55] PHP Notice:  Undefined 
variable: charset in /usr/share/squirrelmail/functions/mime.php on line 317, 
referer: https://xxx.fysik.dtu.dk/src/right_main.php

-- 
Ole Holm Nielsen
Department of Physics, Technical University of Denmark