If you're wanting to access additional API services on http://postmarkapp.com/ and are using the Zend Framework for PHP then Service_Postmark might be of use to you. At the moment the only additional API services offered are for interacting with bounces but as more is added I'll update the code.
$service = new Service_Postmark(); $service->getDeliveryStats(); $servuce->getBounces(); $servuce->getBounce(); $servuce->getBounceTags(); $servuce->activateBounce();
The code is available on github http://github.com/phiali/service_postmark