importing old mail into roundcube

[DumbWizard]

Anyone know how to import old mail into roundcube?  I have a user who wants to migrate his old emails over to a new roundcube webmail server I just finished setting up.  What file format do I need, and where do I save them on the server HDD?

Using a Mac Mini Server (OSX 10.8.5 and server 2.2.1)

Thanks in advance to anyone that helps!

[ABerglund]

Roundcube is a web-based IMAP client, not a mail server. It does not store any mail, that is done on the mail server that it connects to. To migrate mail you'll need to work with the IMAP server, not Roundcube.