My round cube 0.31 server corrupted, luckily I had backup, I decided to install round cube 4.2, and populate the old database to it, everything went fine except that when a user who was created from a backup login , the Sent, Drafts, Junk and Trash are not created automatically, I have to manually create them after a user logs in, although I have set $rcmail_config['create_default_folders'] = TRUE; in main.inc.php,
The folder are successfully created automatically when I create a new user.