[Dovecot] Strange virtual users issues

[Ovi C]

Hi i'm using  dovecot with virtual users from a postgresql database backend on a Debian Lenny system.
I'm using qmail as MTA. Mostly everything seems to work ok , except the fact that the mail delivered never reaches virtual user's INBOX.
Here's the dovecot config: 

dovecot -n
# 1.0.15: /etc/dovecot/dovecot.conf
base_dir: /var/run/dovecot/
log_path: /var/log/dovecot.log
log_timestamp: %Y-%m-%d %H:%M:%S
protocols: imap
ssl_disable: yes
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
login_greeting: Server ready to process requests.
login_process_per_connection: no
max_mail_processes: 512
verbose_proctitle: yes
first_valid_gid: 61
last_valid_gid: 2003
mail_privileged_group: mail
mail_location: maildir:~/Maildir
mail_debug: yes
mail_plugins: quota autocreate
imap_client_workarounds: outlook-idle delay-newmail
auth default:
  mechanisms: plain login digest-md5
  passdb:
    driver: pam
  passdb:
    driver: passwd
  passdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  userdb:
    driver: passwd
  userdb:
    driver: sql
    args: /etc/dovecot/dovecot-sql.conf
  userdb:
    driver: prefetch
  socket:
    type: listen
    client:
      path: /var/run/dovecot/auth-client
      mode: 432
    master:
      path: /var/run/dovecot/auth-master
      mode: 384
      user: root
      group: mail
plugin:
  quota: maildir
  acl: vfile:/etc/dovecot-acls
  trash: /etc/dovecot-trash.conf
  lazy_expunge: .EXPUNGED/ .DELETED/ .DELETED/.EXPUNGED/
  autocreate: Trash
  autocreate2: Spam

The setup is as follows:
I've created a system user named vmail in /home with a group also called vmail.
The virtual users are created in /home/vmail/username when i configure an account from thunderbird.
If I send an message from a virtual user to an system user everythings is ok. The system user get's the mail in his Maildir.
But if I send a message from the system user to the virtual user the MTA's log says that the message has been delivered but it never reaches virtual user's INBOX.

Here's a snip from logs both qmail's and dovecot's:
cat /var/log/qmail.log
status: local 0/10 remote 0/20
new msg 155041
info msg 155041: bytes 263 from <caretaker at localhost.> qp 4560 uid 1000
starting delivery 1: msg 155041 to remote akkersson at localhost.
status: local 0/10 remote 1/20
new msg 155147
info msg 155147: bytes 438 from <caretaker at localhost.> qp 4563 uid 64011
starting delivery 2: msg 155147 to local akkersson at localhost
status: local 1/10 remote 1/20
delivery 1: success: 127.0.0.1_accepted_message./Remote_host_said:_250_ok_1241272738_qp_4563/
status: local 1/10 remote 0/20
end msg 155041
delivery 2: deferral:
status: local 0/10 remote 0/20

cat /var/log/dovecot.log

dovecot: 2009-05-02 16:30:46 Info: Dovecot v1.0.15 starting up
dovecot: 2009-05-02 16:30:46 Info: auth(default): pgsql: Connected to maildb
dovecot: 2009-05-02 16:32:00 Info: IMAP(akkersson): Loading modules from directory: /usr/lib/dovecot/modules/imap
dovecot: 2009-05-02 16:32:00 Info: IMAP(akkersson): Module loaded: /usr/lib/dovecot/modules/imap/lib10_quota_plugin.so
dovecot: 2009-05-02 16:32:00 Info: IMAP(akkersson): Module loaded: /usr/lib/dovecot/modules/imap/lib11_autocreate_plugin.so
dovecot: 2009-05-02 16:32:00 Info: IMAP(akkersson): Effective uid=2003, gid=61, home=/home/vmail/akkersson
dovecot: 2009-05-02 16:32:00 Info: IMAP(akkersson): maildir: data=/home/vmail/akkersson/Maildir
dovecot: 2009-05-02 16:32:00 Info: IMAP(akkersson): maildir: root=/home/vmail/akkersson/Maildir, index=/home/vmail/akkersson/Maildir, control=, inbox=
dovecot: 2009-05-02 16:32:00 Info: imap-login: Login: user=<akkersson>, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, secured
dovecot: 2009-05-02 16:58:11 Info: IMAP(akkersson): Disconnected: Logged out

but akkersson's INBOX is empty..

Any hints ??