Tool to copy IMAP folders from one server to another

I need a Unix-based tool, such as a shell script or command-line program, to copy IMAP folders from one server to another. Ideally, the tool should copy all the folders for a single account (Inbox, Sent, Trash, and user-created folders) at once, rather than one folder at a time. It should preserve message dates. As an option, I'd like to be able to copy just a single IMAP folder.

Alternatively, is there a tool to copy an mbox file to an IMAP server? I have direct access to the mbox files in the filesystem, but not to the filesystem of the remote IMAP server.

Edit: Is there a way for a user to migrate their own questions to Server Fault?

check also imapsync, a great tool !!!

Take a look at offlineimap - it can sync multiple imap servers, do server-to-maildir, and probably the other way around as well.

I'm a "fan" of these perl utils: http://www.athensfbc.com/imap_tools/ and have used them a fair bit