$cm = new ClientManager('vendor/webklex/php-imap/src/config/imap.php');                      
$client = $cm->make([
    'host'          => 'outlook.office365.com',                
    'port'          => 993,
    'encryption'    => 'ssl',
    'validate_cert' => false,
    'username'      => $mailadresi,
    'password'      => $accesstoken,
    'protocol'      => 'imap',
    'authentication' => "oauth"
]);

try {
    $client->connect();
    $folder = $client->getFolder('Inbox');
    $messages = $folder->messages()->all()->get();

    foreach($messages as $message){
        $baslik =@ imap_utf8($message->getSubject());
        echo $baslik."<br /><br />";
    }

} catch (Exception $e) {
    echo 'Exception : ',  $e->getMessage(), "\n";
}