[Dovecot] user lookups not working when using dovecot as lda

[Sven]

Hi

Currently I'm using local from postfix for delivering mails. Now I want 
to change this to using the dovecot lda as I want to use plus addressing.

I configured postfix to use dovecot as I found in the wiki and several 
howtos in the net.

My Problem is the following: dovecot delver accepts the mail but bounces 
it with error: user unknown.

Logging in and authentication via imap4 and pop3 works, only deliver 
seems to be unable to lookup the users from userdb.

Has anyone an idea where my mistake is?

Here is my actual configuration:
dovecot version: 1.0.beta9
postfix version: 2.2.10
system: FreeBSD 6.1-STABLE
The system is using maildirs.

I changed my postfix/master.cf to the following:

dovecot unix    -       n       n       -       -      pipe
   flags=DRhu user=dovecot:dovecot 
argv=/usr/local/libexec/dovecot/deliver -d ${recipient}  -m ${extension}


In my postfix/main.cf I use the following:

dovecot_destination_recipient_limit = 1
local_transport = dovecot


lda & auth specific settings from my dovecot.conf:

protocol lda {
   postmaster_address = postmaster at my-domain.org
   hostname = mail.my-domain.org
   #mail_plugins =
   #mail_plugin_dir = /usr/local/lib/dovecot/imap
   sendmail_path = /usr/sbin/sendmail
   auth_socket_path = /var/run/dovecot/auth-master
   log_path = /var/log/dovecot-deliver.log
   info_log_path = /var/log/dovecot-deliver.log
   # syslog_facility = mail
}

auth_executable = /usr/local/libexec/dovecot/dovecot-auth
auth_process_size = 256

auth_debug = yes
auth_verbose = yes

auth default {
   mechanisms = plain
   passdb pam {
   }
   userdb passwd {
   }
   user = root
   socket listen {
     master {
       path = /var/run/dovecot/auth-master
       mode = 0666
       user = dovecot
       group = dovecot
     }
     client {
       path = /var/run/dovecot/auth-client
       mode = 0660
     }
   }
}

plugin {
}


Any help is appreciated as I dont know where to look for my mistake.

regards,
Sven