I have a user who tried to import a PST file using the Outlook File/Import functionality. The PST in question had most of its messages located in the root folder. As such, Outlook dutifully uploaded those messages into the Zimbra USER_ROOT (/) folder. The only reason I even noticed this is because Outlook (Zimbra connector) appeared to be having troubles importing messages with X.500 style addresses.
Anyway, these messages are basically invisible to this user. I've tried mounting the user's folder via the DAV interface, but the messages themselves are not exposed this way. I've also tried mounting this user's folder into my hierarchy and looking at it with IMAP, but it appears that Zimbra is showing the user's root folder as unable to contain messages (I forget the exact IMAP semantic for this). With the user's full mailbox mounted inside my folder list, I *can* see the messages in the USER_ROOT folder in the Web UI. This is the only way I've been able to see them so far. zmmailbox doesn't even seem to have what I'm looking for. All I need to do is clear out *all* items from, but *only* from the USER_ROOT folder. There are about 5K messages in there from the import, so going through them via the Web UI would be rather slow.