[Dovecot] virtualfolders all mails minus duplicates

[Francesco]

Hello everyone,
i'm trying to mess up a bit with virtual folders and i'm trying to
perform something like this:

i'd like to create an IMAP virtual folder which shows me all the emails
in in INBOX and subfolders but by removing "duplicates"

what i mean as duplicates? simply i can recognize duplicate emails as
the ones with the same message-id in the header (this was just an idea).

in that way if i have a message which is present in more then one folder
then it's displayed only once.

i considered the idea of using message-id in the header as a criteria,
but i don't know if this can be done in this way or in any way at all.

any suggestion is really welcome.

i'm using dovecot 1.2.15.

this is a namespace example just for reference:

for INBOX:
namespace private {
     separator = .
     prefix = INBOX.
     #subscriptions = yes
     #list = no
     inbox = yes
}

for virtuals:
namespace private {
  prefix = v.
  separator = .
  location = virtual:/var/utenti/%Ld/%n/VirtualFolders
  list = yes
  inbox = no
  subscriptions = yes
  hidden = no
}

as of now i'm running a virtualfolder which shows messages flagged as
important which is done like this:

INBOX
INBOX.*
  all flagged

hope you can provide me with some hints.

Thanks very much
Francesco