Well, I'm in the process of doing this, along with moving to a new mail server and consolidating all messages, including inboxes, into a single set of directories per user.
I'm moving e-mail from a remote server mounted /mnt/inboxes (the remote server's /var/mail directory) and /mnt/users (the remote server's /home/users directory) and converting them and -lacing them under /home/users/<username> with the mailfolders being within a directory "Maildir" below the virtual home directory.
The scripts I'm attaching are more complex due to historical reasons where we used the UW IMAP server and some users didn't set a "Mail/" prefix in their client settings so I'm having to search their whole home directory space for mail folders!
Steve
Computer Systems Administrator, E-Mail:-steve@earth.ox.ac.uk Department of Earth Sciences, Tel:- +44 (0)1865 282110 University of Oxford, Parks Road, Oxford, UK. Fax:- +44 (0)1865 272072