Migration from foriegn IMAP mailboxes

[CYRUS LIST]

Has anyone done a script to migrate folder and mail data from a foreign IMAP
sever?

Basically, I need to automate the procedure of a client logging into both
old and new IMAP servers, and for each folder, create the folder, and for
each message, copy the message, recursively through the entire account.
Auth information would be known for both sides, but may not be the same.

Kind regards,  Stuart.