[Dovecot] dovecot and postfix virtual mailbox domains

[Dave]

Hello,
    I'm trying to get dovecot and postfix virtual domains working on an fc6 
system. My software versions are postfix 2.4.5 installed from rpm and 
dovecot 1.0.3 also installed from rpm.
    I'm only running secure protocols, pop3s at the moment, imaps later on. 
I've set up postfix for virtual mailbox domains as per it's howto on the 
subject and confirmed that email sent gets delivered to the virtual area, 
which in this case is /home/vmail/domain.com/username, there's a maildir 
under that. In this case the user is a shell user who has a login, in all 
other cases the users will be completely virtual, having no login account 
and being completely virtual. When i atempt to get mail from the server 
using this user, the one with the login, i am getting a can not map username 
coming from dovecot.
Here's my config:

# 1.0.3: /etc/dovecot.conf
base_dir: /var/run/dovecot/
log_path: /var/log/dovecot
info_log_path: /var/log/dovecot.info
protocols: pop3s
ssl_ca_file: /etc/dovecot/ca-cert.pem
ssl_cert_file: /etc/dovecot/pop.cert
ssl_key_file: /etc/dovecot/pop.key
ssl_cipher_list: ALL:!LOW
disable_plaintext_auth: yes
login_dir: /var/run/dovecot/login
login_executable: /usr/libexec/dovecot/pop3-login
valid_chroot_dirs: /var/spool/vmail
mail_extra_groups: mail
mail_location: maildir:/home/vmail/%d/%u
maildir_copy_with_hardlinks: yes
mail_executable: /usr/libexec/dovecot/pop3
mail_plugin_dir: /usr/lib64/dovecot/pop3
auth default:
  mechanisms: plain login
  verbose: yes
  passdb:
    driver: passwd
  userdb:
    driver: passwd

I'd appreciate any pointers. I think i am close, but am not seeing it.
Thanks.
Dave.