PHPMailer autoload.php not able to open

   //Set the hostname of the mail server
    $mail->Host = 'smtp.gmail.com';

    //Set the SMTP port number - 587 for authenticated TLS, a.k.a. RFC4409 SMTP submission 465 ssl
    $mail->Port = 465;

    //Set the encryption system to use - ssl (deprecated) or tls
    $mail->SMTPSecure = 'ssl';

composer require phpmailer/phpmailer

<?php

namespace Random;

use Exception;

class Whatever
{
    public function whatever()
    {
        throw new Exception();
    }
}

<?php

namespace Random;

class Whatever
{
    public function whatever()
    {
        throw new \Exception();
    }
}

class Autoload
{
    public static function load($className) {
        $className = strtolower($className);
        require_once $className.".php";
    }
}
spl_autoload_register("Autoload::load");