[Dovecot] Thunderbird IMAP woes

[Tamas Kadar]

Hi,

I'm a new dovecot user. We've actually just migrated our email system 
from Courier-IMAP to Dovecot (2.0 rc5) cause we were choking on IO and 
resources, and dovecot's cache and indexing really seems to help, not to 
mention the awesome amount of options, tweaks, and extra features, so 
far, I'm lovin' it. However, we're having a few issues with Thunderbird 
and I wonder if anyone could help. I know it's probably not dovecot's 
fault (some issues we already had with Courier...) but maybe some tweaks 
or settings could help. So here it goes:

We have about 40 users, with their own mailboxes. About half of them 
have access to a HUGE public folder with many many subfolders (think 60 
GB of email in Maildir format), it's organized into divisions and 
clients and projects (and subprojects and whatnot).

We have ACLs controlling the public folder's access (courier-acl file).

It goes like this, for a typical user that has access to the public part:

- Inbox
- Drafts
- Trash
- Sent
- Some important folter
- Some other important folder
+ SHARED
|-- Finances
|--|-- PriceWaterhouseCooper
|--|-- ErnestandYoung
|--|--|-- First project
|--|--|-- Second project
|--|-- Deloitte
|--|--|-- Some project
|--|--|-- Super important project
|-- Health Care
|-- Automotive
|-- IT
|--|-- Microsoft
|--|--|-- That Windows 8 project
|--|-- IBM
|--|--|-- Reviving OS/2 project
|--|--|-- What's eComStation project
|--|-- HP

(not the actual structure, but a very close analogy to what we have here)

So yeah, a public folder with lots of subfolders, sub-subfolders, 
sub-sub-sub-subfolders, sub-sub-sub-sub-subfolders...

Now, the problem is that to a lesser extent, Thunderbird 2, and to a 
larger extent Thunderbird 3 is having serious issues when I go (want to 
go) deeper than two levels of nesting. Like, in the Subscribe dialog 
sometimes I see the third level subfolders, sometimes I dont. If is 
subscribe to a second-level folder, then create a subfolder in it, the 
other subfolders suddenly appear. It's all very random, unfortunatelly, 
then only way I can use the system right now is to uncheck 'Show 
subscribed folders only' in Account Settings, and even then, sometimes 
folders disappear or reappear that are highly nested.

Other clients seem to work fine, but we like Thunderbird cause of the 
add-ons, for example.

Output of dovecot -n:

# 2.0.rc5: /usr/local/etc/dovecot/dovecot.conf
# OS: Linux 2.6.26-2-xen-amd64 x86_64 Debian 5.0.5
auth_mechanisms = plain login
disable_plaintext_auth = no
listen = *
mail_location = ~/Maildir
mail_plugins = acl
maildir_very_dirty_syncs = yes
namespace {
   inbox = yes
   location =
   prefix =
   separator = .
   type = private
}
namespace {
   location = maildir:/home/_shared/projects:INDEX=~/Maildir/_shared
   prefix = shared.
   separator = .
   subscriptions = no
   type = public
}
passdb {
   driver = pam
}
plugin {
   acl = vfile
}
protocols = imap pop3
service imap-enable-acl-groups {
   executable = script-login /home/enable_acl.sh
   user = root
}
service imap {
   executable = imap imap-enable-acl-groups
}
ssl_cert = </etc/ssl/certs/dovecot.pem
ssl_key = </etc/ssl/private/dovecot.pem
userdb {
   driver = passwd
}
verbose_proctitle = yes
protocol imap {
   mail_max_userip_connections = 10
   mail_plugins = $mail_plugins imap_acl
}

Thanks for the help in advance, and keep up the good work,
Tamás Kádár