[Dovecot] OE pop3 > imap subfolder migration?

[Sysadmin]

Hello.

This isn't actually a dovecot question, but I'm running in clienys
servers dovecot mostly as pop3 server and now started to migrate some
servers to imap.

But as clients uses Outlook Express how to transfer their pop3 settings
and mailboxes to imap?. Making a new mail account for imap is easy, and
drag & drop the default folders (inbox, outbox etc) messages to imap
accounts default folders is easy, but what about subfolders? Some users
have hundreds subfolders and creating them & transfering messages by
hand is a pain.

So have anyone a better and faster solution how to migrate Outlook
Express pop3 account to the imap account, preserving the same folders,
rules etc.

-- 
Sysadmin