A Laravel rule to ensure Gmail emails actually exist

ValidGmailAddress.php

<?php

namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class ValidGmailAddress implements Rule
{
    /**
     * Determine if the validation rule passes.
     *
     * @param  string  $attribute
     * @param  mixed  $value
     * @return bool
     */
    public function passes($attribute, $value)
    {
        $response = Http::post('https://accounts.google.com/InputValidator?resource=signup&service=mail', ['input01' => [
            'Input' => 'GmailAddress', 'GmailAddress' => Str::before($value, '@gmail.com'), 'FirstName' => '', 'LastName' => ''
	], 'Locale' => 'en'])->json();
      
        return data_get($response, 'input01.ErrorMessage') == 'That username is taken. Try another.';
    }

    /**
     * Get the validation error message.
     *
     * @return string
     */
    public function message()
    {
        return 'The provided :attribute is not a valid Gmail address.';
    }
}

Great! For those like me, who are looking for the HTTP equivalent:

POST /InputValidator?resource=signup&service=mail HTTP/1.1
Host: accounts.google.com
Content-Type: application/json
Content-Length: 176

{
    "input01": {
        "Input": "GmailAddress",
        "GmailAddress": "example@gmail.com",
        "FirstName": "",
        "LastName": "",
        "Locale": "en"
    }
}

Additional

$valid_google = $response['input01']['Valid'];
if ($valid_google == true || ($valid_google == false && $response['input01']['ErrorMessage'] == 'This username isn't allowed. Try again.')) {
        return true;
    } else {
        return false;
}