Linux Mail Server Setup and Howto Guide

I am running Dovecot and Postfix on Fedora 12 as a mail server. I need to come up with a way to backup all of the mailboxes to either a windows share/server or an external hard drive (the windows share would be my preferred place).

Everything needs to be done from a script via the command line (would like to be able schedule the backup to run automatically). The previous Admin that setup this server removed all forms of GUI except the command line.

Any help would be appreciated.

I looked at that article but it does not really fit (I think), it looks like it is a command to backup a single user's mailbox. I need to backup all of them. Is there not a way to backup postfix mailboxes globally? Or do you need to write a script for each users mailbox separately (that would be a nightmare for keeping updated when users come and go from the company)?