Mbox and Maildir are the two supported formats for local mail storages, both in their most simple formats.
If you want to read from a Mbox file you only need to give the filename to the
constructor of Zend_Mail_Storage_Mbox:
<?php
$mail = new Zend_Mail_Storage_Mbox(array('filename' =>
'/home/test/mail/inbox'));
Maildir is very similar but needs a dirname:
<?php
$mail = new Zend_Mail_Storage_Maildir(array('dirname' =>
'/home/test/mail/'));
Both constructors throw a Zend_Mail_Exception if the storage
can't be read.