Отправка электронной почты, когда у нас есть API? Sendgrid

Я пытаюсь отправить письмо с php, используя sendgrid, и я не могу это сделать

Я использую этот код

<?php
require 'vendor/autoload.php'; // If you're using Composer (recommended)
// Comment out the above line if not using Composer
// require("<PATH TO>/sendgrid-php.php");
// If not using Composer, uncomment the above line and
// download sendgrid-php.zip from the latest release here,
// replacing <PATH TO> with the path to the sendgrid-php.php file,
// which is included in the download:
// https://github.com/sendgrid/sendgrid-php/releases

$email = new \SendGrid\Mail\Mail();
$email->setFrom("[email protected]", "test1");
$email->setSubject("Subject example");
$email->addTo("[email protected]", "Example");
$email->addContent("text/plain", "and easy to do anywhere, even with PHP");
$email->addContent(
"text/html", "<strong>and easy to do anywhere, even with PHP</strong>");
$sendgrid = new \SendGrid(getenv('SENDGRID_API_KEY'));
try {
$response = $sendgrid->send($email);
print $response->statusCode() . "\n";
print_r($response->headers());
print $response->body() . "\n";
} catch (Exception $e) {
echo 'Caught exception: '. $e->getMessage() ."\n";
}

и я получаю эту ошибку

401 Array ( [0] => HTTP/1.1 401 Unauthorized [1] => Server: nginx [2] => Date: Tue, 30 Oct 2018 08:11:54 GMT [3] => Content-Type: application/json [4] => Content-Length: 88 [5] => Connection: keep-alive [6] => Access-Control-Allow-Origin: https://sendgrid.api-docs.io [7] => Access-Control-Allow-Methods: POST [8] => Access-Control-Allow-Headers: Authorization, Content-Type, On-behalf-of, x-sg-elas-acl [9] => Access-Control-Max-Age: 600 [10] => X-No-CORS-Reason: https://sendgrid.com/docs/Classroom/Basics/API/cors.html [11] => [12] => ) {"errors":[{"message":"Permission denied, wrong credentials","field":null,"help":null}]}

Я использовал этот учебник, быстрый старт, idk, что делать, заранее спасибо.
https://github.com/sendgrid/sendgrid-php