[Dovecot] Local + virtual users using Dovecot 0.99.10.6 (from debian testing)

[Alexander]

Hi,

I have configured the MTA (exim4) to put the messages for my local users
at /var/mail.
If the user does not exist as true unix user, it looks at a postgresql database and if the user exists there, it delivers the message at /var/mail/virtual

Example: User fred is a unix user, and peter is a virtual user.

If i send a mail to fred at mydomain.org, the message is stored at
/var/mail/fred (im using exim's append for transport).

If i send a mail to peter at mydomain.org, the message is stored at
/var/mail/virtual/peter


With the defaul configuration from debian, dovecot is capable serving
the local users mailbox (and its working at the moment). Im using only
IMAP (i see there is an option for pop3, but im not interested in that
atm).

I think i know how to change the config file to serve only
virtual users using the postgres module.

Can anyone tell me how to serve them both at the same time? 
As I understand it, what i need is to make dovecot try to validate a user
againt the local user database (its using pam for that at the moment),
and if it fail, try with postres. But i dont know how (or if its
possible at all).


Thanks.