As I posted in the smeplus thread, the update without apache (db4), securemail (ssl-imap) and double-bounce, the cyrus-imap could not authenticate.
Without this folder sharing, I don't think SME-Server is appropriate to support groupware. The trend toward such a imap server as cyrus is well known. It will be better to look at Kolab2 dispite the problem of managing a different distro.