When I convert my main machine from FC1 to FC2 I want to move from using cyrus imapd to dovecot. It's mainly for simplicity but I also want to use a more standard mail directory format. Unfortunately, I haven't found a way to convert my existing mail to maildir format. There seems to be lots of information on how to convert to the cyrus format but not from it. I really need to keep metainformation like whether or not the message has been read already. Has anyone done this?
First, you could check the dovecot mailing list to see if someone has done this:
http://dovecot.org/
One idea that comes to mind is to set up a temporary box running Dovecot and drag your messages in your client from one server's folder to the other's, letting the client do the work using the IMAP protocol. You can even do this using the mailutil utility that comes with the UW-IMAP package. It uses IMAP protocol to copy or move folders.
