I’m trying to use accessToken to send mail in Microsoft 365.

But when decode accessToken, I realize that it does not have any scopes inside.

So I guess that the reason why I can’t use this accessToken to send Mail.

This is my code to get accessToken before use it to send mail.

<?php
require 'vendor/autoload.php';

use GuzzleHttpClient;
use MicrosoftGraphGraph;

$guzzle = new Client();
$url = 'https://login.microsoftonline.com/' . $tenantId . '/oauth2/v2.0/token';
$token = json_decode($guzzle->post($url, [
    'form_params' => [
        'client_id' => $clientId,
        'client_secret' => $clientSecret,
        'scope' => 'https://graph.microsoft.com/.default',
        'grant_type' => 'client_credentials',
    ],
])->getBody()->getContents());

$accessToken = $token->access_token;

function base64UrlDecode($input) {
    $remainder = strlen($input) % 4;
    if ($remainder) {
        $addlen = 4 - $remainder;
        $input .= str_repeat('=', $addlen);
    }
    return base64_decode(strtr($input, '-_', '+/'));
}

function decodeJwt($jwt) {
    $parts = explode('.', $jwt);
    if (count($parts) === 3) {
        list($header, $payload, $signature) = $parts;
        $decodedPayload = base64UrlDecode($payload);
        return json_decode($decodedPayload, true);
    }
    return null;
}

$decodedToken = decodeJwt($accessToken);

if ($decodedToken) {
    echo "Decoded Token:n";
    print_r($decodedToken);
} else {
    echo "Failed to decode token.";
}

Decoded Token:
Array
(
    [aud] => https://graph.microsoft.com
    [iss] => https://sts.windows.net/tenant_id/
    [iat] => 1721285822
    [nbf] => 1721285822
    [exp] => 1721289722
    [aio] => E2dgYDh/MUzO53mMQvZEb9Xk23da1==
    [app_displayname] => WordPress send mail by PHP library
    [appid] => client_id
    [appidacr] => 1
    [idp] => https://sts.windows.net/150115f9-9fg2-468e-8256-31864c946d38/
    [idtyp] => app
    [oid] => information
    [rh] => information.
    [sub] => information
    [tenant_region_scope] => AS
    [tid] => tenant_id
    [ver] => 1.0
    [wids] => Array
            [0] => 0997a1d0-0d1d-4acb-b408-d5ca73121e90
        )
    [xms_idrel] => 7 4
    [xms_tcdt] => 1691395903
)

Could anyone help me to know what is the issue or what are the missing roles?