/usr/libexec/postfix/smtp does not send mail using Laravel on macOS - php

Question

I have a Laravel 8 project that I want to send emails with. I develop it on macOS and I want to test it, but it does not work, but won't give any errors. (I replaced sensitive data with ********)
.env
MAIL_MAILER=smtp
MAIL_HOST=smtp.gmail.com
MAIL_PORT=465
MAIL_USERNAME=********#gmail.com
MAIL_PASSWORD=********
MAIL_ENCRYPTION=ssl
MAIL_FROM_ADDRESS=********#gmail.com
MAIL_FROM_NAME="${APP_NAME}"
Note: I validated those settings, I also tested other working SMTP settings. So it's not a configuration issue in this file
mail.php
/// ...
'default' => env('MAIL_MAILER', 'mail'),
/// ...
'mailers' => [
'smtp' => [
'transport' => 'mail',
'host' => env('MAIL_HOST', 'smtp.mailgun.org'),
'port' => env('MAIL_PORT', 587),
'encryption' => env('MAIL_ENCRYPTION', 'tls'),
'username' => env('MAIL_USERNAME'),
'password' => env('MAIL_PASSWORD'),
'timeout' => null,
'auth_mode' => null,
],
/// ...
],
/// ...
'markdown' => [
'theme' => 'default',
'paths' => [
resource_path('views/vendor/mail'),
resource_path('views/emails'),
],
],
/// ...
MailController.php
namespace App\Http\Controllers\API;
use Illuminate\Http\Request;
use App\Http\Controllers\Controller as Controller;
use Illuminate\Support\Facades\Mail;
class MailController extends Controller
{
public function testMail(Request $request)
{
$email = '********#live.com';
$data = [
'title' => 'Test mail'
];
Mail::send(['html' => 'emails.testMail'], $data,
function ($message) use ($email, $data) {
$message->to($email)
->subject($data['title']);
});
$response = [
'error' => 0,
'to' => $email,
'data' => $data,
];
return response()->json($response, 200);
}
}
Note: There is a blade template containing only HTML for test purposes at resources/views/emails/testMail.blade.php. I also added the appropriate GET-route.
When I access the endpoint in Postman, I get
{
"error": 0,
"to": "********#live.com",
"data": {
"title": "Test mail"
}
}
Little Snitch popped up, asking if I want to allow /usr/libexec/postfix/smtp to access smtp.gmail.com, so I know the call goes through. I gave the process all rights to access any server and retried, but the mail will never reach my destination.
Yes, I checked the SPAM folder. Yes, I checked other credentials. Yes I tested manual delivery between both accounts. Yes, I tested with Little Snitch disabled, entirely. Yes, I checked the laravel.log and it reveals nothing.
I noticed, that I won't get any error from Laravel when I put in wrong information in the .env file (except when I change MAIL_MAILER).
How can I get the output from the SMTP process to find out what the issue is? How can I fix the issue?