Send mail on google compute engine instance

We’d like to know a little more about the email you’ll be sending through
1. The nature of your business, the services you provide, and your potential customer base
2. Your sending frequency and volume
3. How you collect your recipient addresses
4. How you will allow your recipients to opt out of your emails (whether you plan to use SendGrid’s one-click unsubscribe feature, or if you have your own method)
5. The types of messages you will be sending (transactional or marketing)
 
Could you help us with an answer to the following questions also:
1. Where did you acquire your recipient list?
2. What kind of opt-in process do your recipients go through?
3. How old is your recipient list?
4. When was the last time you communicated with these recipients?
5. How do you maintain your recipient list?

$url = 'https://api.sendgrid.com/';
$pass = 'AK.txxxxxxxxxxxxxxxix';
$params = array(
    'to'        => "[email protected]",
    'subject'   => "test title",
    'html'      => "test content",
    'from'      => "admin" . '<[email protected]>',
  );
 
$header = array(
    'Authorization: Bearer ' . $pass,
);
 
$request =  $url.'api/mail.send.json';
$session = curl_init($request);
curl_setopt ($session, CURLOPT_POST, true);
curl_setopt ($session, CURLOPT_POSTFIELDS, $params);
curl_setopt ($session, CURLOPT_HEADER, false);
curl_setopt ($session, CURLOPT_SSLVERSION, CURL_SSLVERSION_TLSv1_2);
curl_setopt ($session, CURLOPT_RETURNTRANSFER, true);
curl_setopt ($session, CURLOPT_HTTPHEADER, $header);
$response = curl_exec($session);
curl_close($session);