generateMessageId example

if (!$headers->has('Date')) {
            $headers->addDateHeader('Date', new \DateTimeImmutable());
        }

        // determine the "real" sender         if (!$headers->has('Sender') && \count($froms = $headers->get('From')->getAddresses()) > 1) {
            $headers->addMailboxHeader('Sender', $froms[0]);
        }

        if (!$headers->has('Message-ID')) {
            $headers->addIdHeader('Message-ID', $this->generateMessageId());
        }

        // remove the Bcc field which should NOT be part of the sent message         $headers->remove('Bcc');

        return $headers;
    }

    public function toString(): string
    {
        if (null === $body = $this->getBody()) {
            

$p = new MessagePart((new Email())->from('fabien@symfony.com')->text('content')->subject('Subject'));
        $this->assertEquals(new Headers(
            new ParameterizedHeader('Content-Type', 'message/rfc822', ['name' => 'Subject.eml']),
            new UnstructuredHeader('Content-Transfer-Encoding', 'base64'),
            new ParameterizedHeader('Content-Disposition', 'attachment', ['name' => 'Subject.eml', 'filename' => 'Subject.eml'])
        ), $p->getPreparedHeaders());
    }

    public function testSerialize()
    {
        $email = (new Email())->from('fabien@symfony.com')->to('you@example.com')->text('content');
        $email->getHeaders()->addIdHeader('Message-ID', $email->generateMessageId());

        $p = new MessagePart($email);
        $expected = clone $p;
        $this->assertEquals($expected->toString(), unserialize(serialize($p))->toString());
    }
}

if (!$headers->has('Date')) {
            $headers->addDateHeader('Date', new \DateTimeImmutable());
        }

        // determine the "real" sender         if (!$headers->has('Sender') && \count($froms = $headers->get('From')->getAddresses()) > 1) {
            $headers->addMailboxHeader('Sender', $froms[0]);
        }

        if (!$headers->has('Message-ID')) {
            $headers->addIdHeader('Message-ID', $this->generateMessageId());
        }

        // remove the Bcc field which should NOT be part of the sent message         $headers->remove('Bcc');

        return $headers;
    }

    public function toString(): string
    {
        if (null === $body = $this->getBody()) {
            

public function __construct(RawMessage $message, Envelope $envelope)
    {
        $message->ensureValidity();

        $this->original = $message;
        $this->envelope = $envelope;

        if ($message instanceof Message) {
            $message = clone $message;
            $headers = $message->getHeaders();
            if (!$headers->has('Message-ID')) {
                $headers->addIdHeader('Message-ID', $message->generateMessageId());
            }
            $this->messageId = $headers->get('Message-ID')->getId();
            $this->raw = new RawMessage($message->toIterable());
        } else {
            $this->raw = $message;
        }
    }

    public function getMessage(): RawMessage
    {
        return $this->raw;
    }