// save a copy of sent messages?
$_prefs['save_sent_mail'] = array(
    'value' => 1,
    'locked' => false,
    'shared' => true,
    'type' => 'implicit'
);

// sent mail folder
$_prefs['sent_mail_folder'] = array(
    'value' => 'sent-mail',
    'locked' => false,
    'shared' => true,
    'type' => 'implicit'
);
