[CLUE-Tech] postfix delivery to courier-imap shared folder

[Jeff Cann]

Greetings,

I have postfix and courier-imap configured.  I am using postfix's virtual user 
feature to specify virtual users (ones that don't have shell account).  
Postfix is currently configured to deliver virtual user mail to 
/var/spool/vmail/{user} where user is a maildir and is specified in a dbm 
file.  For example:

billing at example.com billing/

tells postfix delivery agent to put mail for 'billing at example.com' into the 
/var/spool/mail/billing/ maildir.

I have created a shared maildir with shared folders for courier-imap.  So, 

shared/            # shared folder
    .billing		# billing 'shared' folder
    .webmaster # webmaster 'shared' folder

The shared folders have the typical maildir subdirectories (cur, new, tmp).

I want postfix to deliver email for billing at example.com to the shared/.billing 
shared folder and webmaster at example.com to the shared/.webmaster folder.  I 
figured postfix wouldn't care since the shared folder is essentially a 
maildir directory.  I was wrong.  Here's what mailq reports:

# mailq
-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
4361DEDABE      780 Fri Sep 12 17:33:33  j.cann at example.org
(mailbox /var/spool/vmail/common/shared/.billing: cannot open file: Is a 
directory)
                                         billing at example.com
-- 0 Kbytes in 1 Request.

So, I'm soliciting suggestions on how to configure postfix to deliver email to 
a courier-imap shared folder.  Do I need a different mail drop program?  I'm 
using the default postfix one.  The courier-imap shared folder docs don't 
talk about delivery (makes sense).  Also, let me add that I'm new to mail 
administration...

Thanks,
Jeff