[imp] IMP's conf.xml -missing "Mail" in selection list app

[IMP]

I can login as Administrator and go to the Configuration page.
However, I cannot find "Mail" select item under the configuration list.
What I only get is the "Address Book (turba)".

Do any one know why?

Here is my configuration under horde/conf/registry.php about turba and imp

$this->applications['imp'] = array(
    'fileroot' => dirname(__FILE__) . '/../webmail',
    'webroot' => $this->applications['horde']['webroot'] . '/../webmail',
    'icon' => $this->applications['horde']['webroot'] .
'/../webmail/graphics/imp.gif',
    'name' => _("IMP Mail"),
    'allow_guests' => false,
    'status' => 'active',
    'provides' => 'mail',
    'menu_parent' => 'mail'
);

$this->applications['turba'] = array(
    'fileroot' => dirname(__FILE__) . '/../../webmail/contacts',
    'webroot' => $this->applications['horde']['webroot'] .
'/../webmail/contacts',
    'icon' => $this->applications['horde']['webroot'] .
'/../webmail/contacts/graphics/turba.gif',
    'name' => _("Address Book"),
    'allow_guests' => false,
    'status' => 'active',
    'provides' => 'contacts',
    'menu_parent' => 'pim'
);