[Dovecot] Multiple private namespace question

[Troy Engel]

(apologies if this has been covered, can't find it on the Wiki/FAQ, etc.)

We have a stellar, fantastic, hard working Dovecot 1.0.5 (yes, I need to 
upgrade) installation running in Courier-IMAP compatibility mode:

   mail_location = maildir:~/Maildir:INDEX=/var/spool/dovecot/indexes/%1u/%u

   namespace private {
     separator = .
     prefix = INBOX.
     inbox = yes
   }

A user purchased a Windows Mobile 6 device which is ignoring the 
namespace (it's the device's bug for sure, other people report it on 
forums around the 'net) and there's no way on this device to manually 
set the Prefix; so, his Sent mails are never making it back to the 
server when replying from the device because of the missing INBOX. issue.

Can I add a second hidden namespace with no prefix:

   namespace private {
     separator = .
     prefix =
     hidden = yes
   }

...to fix his problem, but without adversely affecting anyone else? The 
issue that has given me pause is this comment in the config file:

   "Default namespace is simply done by having a namespace with empty 
prefix."

..but then there's also:

   "If namespace is hidden, it's not advertised to clients via NAMESPACE 
extension or shown in LIST replies."

I'm not sure what exactly will happen by adding a hidden namespace with 
no prefix after an advertised namespace with a prefix; this is a live 
server, so mucking up the works with a bad config is not an option. :)

Anyone have a clue if this is valid/good/correct and Dovecot will play 
nicely?

Many thanks,
-te

-- 
Troy Engel | Systems Engineer
Fluid, Inc | http://www.fluid.com