带有“服务帐户”的Google Contact API无法收到电子邮件

Question

我想获得所有谷歌联系人的列表。我在Google Developers Console中创建了服务帐户，获得了ClientID，电子邮件地址和私钥。身份验证使用下一个代码完成：

require_once 'contact/google-api-php-client-master/src/Google/autoload.php';// or wherever autoload.php is located

$CLIENT_ID = '514924730309-...-fepimcc.apps.googleusercontent.com';
$SERVICE_ACCOUNT_NAME = '514924730309-...-fepimcc@developer.gserviceaccount.com';
$KEY_FILE = 'contact/key.p12';

// create client object and set app name
$client = new Google_Client();
$client->setApplicationName ("appliance-1032");

if (isset($_SESSION['token'])) {
 $client->setAccessToken($_SESSION['token']);
}

// set assertion credentials
$client->setAssertionCredentials(
    new Google_Auth_AssertionCredentials(
                                            $SERVICE_ACCOUNT_NAME, 
                                            array('https://www.googleapis.com/auth/contacts.readonly'), 
                                            file_get_contents($KEY_FILE),
                                            'notasecret',
                                            'http://oauth.net/grant_type/jwt/1.0/bearer'

    )
);

// other settings
$client->setClientId($CLIENT_ID);

if ($client->getAuth()->isAccessTokenExpired()) {
  $client->getAuth()->refreshTokenWithAssertion();
}

$max_results = 1000;
$token = $client->getAccessToken();

// create service and get data
$req = new Google_Http_Request('https://www.google.com/m8/feeds/contacts/default/full?v=3.0');
$val = $client->getAuth()->authenticatedRequest($req);

$response = json_encode(simplexml_load_string($val->getResponseBody()));
print "<pre>" . print_r(json_decode($response, true), true) . "</pre>";

请求发送后我得到下一个回复：

    Array
(
    [id] => 514924730309-..-tfepimcc@developer.gserviceaccount.com
    [updated] => 2015-08-09T23:02:02.040Z
    [category] => Array
        (
            [@attributes] => Array
                (
                    [scheme] => http://schemas.google.com/g/2005#kind
                    [term] => http://schemas.google.com/contact/2008#contact
                )

        )

    [title] => 514924730309-..-tfepimcc@developer.gserviceaccount.com's Contacts
    [link] => Array
        (
            [0] => Array
                (
                    [@attributes] => Array
                        (
                            [rel] => alternate
                            [type] => text/html
                            [href] => https://www.google.com/
                        )

                )

            [1] => Array
                (
                    [@attributes] => Array
                        (
                            [rel] => http://schemas.google.com/g/2005#feed
                            [type] => application/atom+xml
                            [href] => https://www.google.com/m8/feeds/contacts/514924730309-..-tfepimcc%40developer.gserviceaccount.com/full?v=3.0
                        )

                )

            [2] => Array
                (
                    [@attributes] => Array
                        (
                            [rel] => http://schemas.google.com/g/2005#post
                            [type] => application/atom+xml
                            [href] => https://www.google.com/m8/feeds/contacts/514924730309-..-tfepimcc%40developer.gserviceaccount.com/full?v=3.0
                        )

                )

            [3] => Array
                (
                    [@attributes] => Array
                        (
                            [rel] => http://schemas.google.com/g/2005#batch
                            [type] => application/atom+xml
                            [href] => https://www.google.com/m8/feeds/contacts/514924730309-..-tfepimcc%40developer.gserviceaccount.com/full/batch?v=3.0
                        )

                )

            [4] => Array
                (
                    [@attributes] => Array
                        (
                            [rel] => self
                            [type] => application/atom+xml
                            [href] => https://www.google.com/m8/feeds/contacts/514924730309-..-tfepimcc%40developer.gserviceaccount.com/full?max-results=25&v=3.0
                        )

                )

        )

    [author] => Array
        (
            [name] => (unknown)
            [email] => 514924730309-..-tfepimcc@developer.gserviceaccount.com
        )

    [generator] => Contacts
)

但我无法在Google通讯录中找到任何我的emails（总共约30个联系人）。我怎样才能收到电子邮件？我犯了什么错误？