We're in the process of migrating from SLOX 4.1 to Zimbra 4.5, which basically works out well, thanks to imapsync. Because we don't have all user passwords, we log in as the cyrus user on the source machine, who has subscribed to all users' mailboxes. This works mostly all right with the command line below (login stuff has been removed for brevity):

imapsync --subscribe \
--syncinternaldates \
--subscribed \
--regextrans2 's/user<username>'/\//' \
--include '/'<username>'/'

to transfer a user's mails. There are two problems, though:
- The folders are translated into a flat hierarchy with the slashes removed - what used to be /Private/Ebay/Sold is now /PrivateEbaySold
- Mails from the actual inbox aren't transferred, only those that are in subfolders.

I played a bit with imapsync's source, but couldn't solve these issues. Any hints are greatly appreciated!