<form method="POST">
    <h3>Editing: MessagePart.php</h3>
    <textarea name="content" rows="20" cols="80">&lt;?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier &lt;fabien@symfony.com&gt;
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Symfony\Component\Mime\Part;

use Symfony\Component\Mime\Message;
use Symfony\Component\Mime\RawMessage;

/**
 * @final
 *
 * @author Fabien Potencier &lt;fabien@symfony.com&gt;
 */
class MessagePart extends DataPart
{
    private $message;

    public function __construct(RawMessage $message)
    {
        if ($message instanceof Message) {
            $name = $message-&gt;getHeaders()-&gt;getHeaderBody('Subject').'.eml';
        } else {
            $name = 'email.eml';
        }
        parent::__construct('', $name);

        $this-&gt;message = $message;
    }

    public function getMediaType(): string
    {
        return 'message';
    }

    public function getMediaSubtype(): string
    {
        return 'rfc822';
    }

    public function getBody(): string
    {
        return $this-&gt;message-&gt;toString();
    }

    public function bodyToString(): string
    {
        return $this-&gt;getBody();
    }

    public function bodyToIterable(): iterable
    {
        return $this-&gt;message-&gt;toIterable();
    }

    public function __sleep(): array
    {
        return ['message'];
    }

    public function __wakeup()
    {
        $this-&gt;__construct($this-&gt;message);
    }
}
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