onBeforeSendEmail event triggered from Commerce_EmailsService
You don't show what code you're trying to use to access the parameters, but something like this should work from your main plugin class:

public function init()
{
    parent::init();

    craft()-&gt;on('commerce_emails.beforeSendEmail', function($event) {
        $params = $event-&gt;params;

        $craftEmail = $params['craftEmail'];
        $commerceEmail = $params['commerceEmail'];
        $order = $params['order'];
        $orderHistory = $params['orderHistory'];

        ...
    });
}