Dovecot, migrating mailboxes from old to new server and from old to new format?

Hello,

I've got a task to migrate a Dovecot mailstore, mailboxes, public folders, etc from an older server (it runs Dovecot 2.2.x) to a new server (running Dovecot 2.3.x). At the same time I'm needing to change mailbox storage formats, going from Mbox (on old server) to Maildir (on new server). I'm not sure if any of the mailboxes are compressed with zlib or encrypted, there's a lot of them, is there a way to find out compression or encryption and decompress/decrypt them prior to migration?

Suggestions welcome. Thanks. Dave.