/**
 * Once the folder structure has been created it copies messages recursively from the root
 * folder.
 */
private void copySourceMessages(IMAPFolder sourceFolder) throws MessagingException {
    if (sourceFolder != null) {
        final String sourceFolderName = sourceFolder.getFullName();
        final String targetFolderName = sourceFolderNameToTarget(sourceFolderName, sourceIndex,
            targetIndex);
        if ((sourceFolder.getType() & Folder.HOLDS_MESSAGES) == Folder.HOLDS_MESSAGES) {
            //Manage Servers with public/read only folders.
            try {
                sourceFolder.open(Folder.READ_WRITE);
            } catch (ReadOnlyFolderException ex) {
                sourceFolder.open(Folder.READ_ONLY);
            }
            if (sourceFolder.getMode() != Folder.READ_ONLY) {
                sourceFolder.expunge();
            }
            ///////////////////////
            final int messageCount = sourceFolder.getMessageCount();
            sourceFolder.close(false);
            int pos = 1;
            while (pos + MNIMAPSync.BATCH_SIZE <= messageCount) {
                //Copy messages
                service.execute(new MessageCopier(this, sourceFolderName, targetFolderName, pos,
                        pos + MNIMAPSync.BATCH_SIZE, targetIndex.getFolderMessages(
                                targetFolderName)));
                pos = pos + MNIMAPSync.BATCH_SIZE;
            }
            service.execute(new MessageCopier(this, sourceFolderName, targetFolderName, pos,
                    messageCount,
                    targetIndex.getFolderMessages(targetFolderName)));
        }
        //Folder recursion. Get all children
        if ((sourceFolder.getType() & Folder.HOLDS_FOLDERS) == Folder.HOLDS_FOLDERS) {
            for (Folder child : sourceFolder.list()) {
                copySourceMessages((IMAPFolder) child);
            }
        }
    }
}