ZF2在模块之间共享模型

Hi I'm trying to share models between my modules, but when I call my getServiceLocator()->get('Mail\Model\Mail') in my controller from another module the class cannot be found.

I'm searching for a solution for a few days now, but I can't find one thats working for me.

public function getServiceConfig()
{
    return array(
        'factories' => array(
            'Mail\Model\Mail' => function($sm) {
                $mail = new Mail();
                return $mail;
            },
            'Mail\Model\MailTable' => function($sm) {
                $tableGateway = $sm->get('MailTableGateway');
                $table        = new MailTable($tableGateway);
                return $table;
            },
            'MailTableGateway' => function($sm) {
                $dbAdapter          = $sm->get('Zend\Db\Adapter\Adapter');
                $resultSetPrototype = new ResultSet();
                $resultSetPrototype->setArrayObjectPrototype(new Mail());
                return new TableGateway('mail', $dbAdapter, null, $resultSetPrototype);
            }
        )
    );
}

When I return a string instead it's working fine so the I know I'm calling the right key, but when I try to return my class it can't be found.

In my mail module the class is working fine.. If you need more information please let me know.

Thanks in advance!