Sendgrid emails array included in the header - php

Question

I run this script to send to each user an email. Mails are sent ok(one to each user), but in the email sent all the others adresses are shown in the headers.
$all_users = array(); // intialzie array
while ($usuario = mysqli_fetch_array($resultado, MYSQLI_ASSOC)) {
$usermail = $usuario['email'];
$hash = $usuario['hash'];
mysqli_query($dbc, "UPDATE newsletter SET enviado = '1' WHERE email='$usermail' ");
$all_users[] = $usermail; // push all emails first
}
// then send
try {
$email->setTos($all_users)
->setFrom("no_responder#test.com.ar")
->setFromName("test")
->setReplyTo("no_responder#test.com.ar")
->setSubject("Test")
->setHtml('test');
$result = $sendgrid->send($email);
echo "enviado";
} catch(\SendGrid\Exception $e) {
echo $e->getCode() . "\n";
foreach($e->getErrors() as $er) {
echo $er;
}
}
?>
How can i hide other emails while sending them individually using sendgrid (bcc - blind carbon copy)?

Answer 1

Have you updated your SendGrid PHP library? The newest version uses v3 of the WebAPI, which corrects the confusing To: array functionality.
The issue is that what you're doing right now is populating the native SMTP-level To, which is why you can see all the addresses. In the v2 API, you'd need to instead populate the x-smtpapi field's to array, to make sure SendGrid splits out all the addresses.
I'd strongly recommend updating your PHP Library & leveraging the v3 API, which removes this confusion, and lets you setup each recipient in a more logical manner.