binc 1.2 / Maildir++ depot

Recently we have been getting some serious problems with binc on our 
imapservers.

This isnt flame but why is binc restricted to creating mailboxes under 
INBOX<delimiter> ?

The most current problem is that ALL our new thunderbird clients can't 
use Sent Drafts or Trash since they are common to be stored in the root 
and not in INBOX.Sent .

I've been trying to find some draft or rfc that explains the default 
setup of IMAP/Maildir folders but I can't find anything like that, 
everything i find says its up to the implementation do deside.

So my question is, what are the reasons for restricting mailboxes 
outside INBOX/ ?

-- 
Jerry Lundström, System Developer
Section for IT and Media, Stockholms University, Sweden
+46 (0)8 16 19 99 / http://www.it.su.se