index.php

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

// Create the Transport
$transport = (new Swift_SmtpTransport('localhost', 1025));

// Create the Mailer using your created Transport
$mailer = new Swift_Mailer($transport);

// Create a message
$message = (new Swift_Message('Wonderful Subject'))
  ->setFrom(['john@doe.com' => 'John Doe'])
  ->setTo(['receiver@domain.org', 'other@domain.org' => 'A name'])
  ->setBody('Here is the message itself');

// Send the message
$result = $mailer->send($message);

if($result) {
  echo '<h1>MESSAGE SENT</h1>';
} else {
  echo 'Email failed'; 
}