Please have a look here:
Also check the values of php_value "upload_max_filesize", "upload_max_filesize" within your php.ini file.
Within your RoundCube web, RoundCube has its own logfiles.
Do you see any errors there?
You can configure that within RoundCube's configuration file called main.inc.php
Do not worry about deleted "default" folders. They are created automaticly again, when mail arrives.
Within your main.inc.php have a look to these lines, in the last line you can set permissions for the default folders by using TRUE or FALSE:
The first line defines the default path, folders from there are displayed. You should check that as well.
// only list folders within this path
$rcmail_config['imap_root'] = '';
// store draft message is this mailbox
// leave blank if draft messages should not be stored
$rcmail_config['drafts_mbox'] = 'Drafts';
// store spam messages in this mailbox
$rcmail_config['junk_mbox'] = 'Junk';
// store sent message is this mailbox
// leave blank if sent messages should not be stored
$rcmail_config['sent_mbox'] = 'Sent';
// move messages to this folder when deleting them
// leave blank if they should be deleted directly
$rcmail_config['trash_mbox'] = 'Trash';
// display these folders separately in the mailbox list.
// these folders will automatically be created if they do not exist
$rcmail_config['default_imap_folders'] = array('INBOX', 'Drafts', 'Sent', 'Junk', 'Trash');
// protect the default folders from renames, deletes, and subscription changes
$rcmail_config['protect_default_folders'] = TRUE;