//401mail_hdr
// Display custom headers (configured via the identity screen) when viewing
// messages?
$_prefs['mail_hdr'] = array(
    'value' => '',
//  'value' => "Message-ID\nX-Spam-Level",
    'locked' => false,
    'shared' => false,
    'type' => 'textarea',
    'desc' => _("Additional headers to display when viewing: <em>(optional, enter each header on a new line)</em>"));

