[Dovecot] Filtering virtual mailbox using other virtual mailbox?

[Giovanni Giorgi]

Hi All,
  my name is Giovanni and I am new to dovecot.
I have installed version 2.0  the past week and I find it very powerful.
I have started to play with the virtual mailbox plugin.
I was unable to do a virtual mailbox filtering out the contents of  
other mailbox, for instance

I have a virtual/spam mailbox which filter out all the spam thanks to  
spamassassin. This mailbox is virtual, its description is
INBOX
-Trash
-Trash/*
-Junk
  subject SPAM


I'd like to do a simple virtual/ham mbox using this dovecot-virtual

INBOX
-virtual/spam
  to: jj at gioorgi.com

but it seems not working. it does not filter the spam.

It is possible to do such thing, or I am trying to do something not  
possible at all?
Thank you

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Giovanni Giorgi
jj at gioorgi.com