A very minor bug but in /includes/languages/english/email_extras.php, OFFICE_IP_TO_HOST_ADDRESS is defined twice. Once with..
PHP Code:
if (!defined('OFFICE_IP_TO_HOST_ADDRESS')) define('OFFICE_IP_TO_HOST_ADDRESS', 'OFF'); 
...and later with...
PHP Code:
// for when gethost is off
  define('OFFICE_IP_TO_HOST_ADDRESS', 'Disabled'); 
This is in ZC 1.3.9a (and ZC 1.3.8).

Regards,
Christian.