Well title asks it all, is it possible for me to migrate over 300+ users from Qmail toaster - vpopmail - Courier Imap to Postfix - Dovecot Imap?

Here's the dir format and as I see it they both use maildir format;
## Current Mail Server (qmail)

## Newly setuped Mail server (postfix)

If its all possible how? What I wanna do is access the existing Mail structure that would be migrated from qmail to postfix.

If you need to ask me more about this and that with the existing mail server (qmail) and the plan to be replacement mail server (postfix) specs just post away.

Thanks in advance,