how to deliver to subfolder? cyrus-imapd 1.5.19

[Florian Ehrenthal]

hi list,

i am somewhat new to cyrus-imapd, but now i am facing a problem that i cannot 
solve. my setup is the following:
debian woody. cyrus-imapd version 1.5.19

postfix main.cf:
mailbox_transport: procci

postfix master.cf:
procci	  unix		-	n	n	-	-	pipe
  user=cyrus argv=/usr/bin/procmail EXTENSION="${extension}" USER="${user}"

procmailrc:
:0 fw
| /usr/bin/spamc		# piping through spamd (spamassassin)

:0
| /usr/sbin/cyrdeliver -e -m "$EXTENSION" "$USER"

now what's the problem you ask? well, so far everything works fine. but i want 
to deliver the mails identified as spam into an user's special subfolder.
but i can't get it to work.
i have created one mailbox user.testuser and a subfolder Junk with all rights, 
but running
cat main_from_textfile | deliver -e -m Junk testuser  delivers the mail to 
INBOX and not to its subfolder Junk.

can someone please enlighten me, how to solve my problem?

thanks in advance!
Florian