src/Viserio/Component/Mail/Transport/PostmarkTransport.php
public function send(Swift_Mime_SimpleMessage $message, &$failedRecipients = null): int
    {
        $this->beforeSendPerformed($message);

        $version = \PHP_VERSION ?? 'Unknown PHP version';
        $os      = \PHP_OS      ?? 'Unknown OS';

        $response = $this->client->post(
            $this->url,
            [
                'headers' => [
                    'X-Postmark-Server-Token' => $this->serverToken,
                    'Content-Type'            => 'application/json',
                    'User-Agent'              => "postmark (PHP Version: ${version}, OS: ${os})",
                ],
                'json' => $this->getMessagePayload($message),
            ]
        );

        $message->getHeaders()->addTextHeader(
            'X-PM-Message-Id',
            $this->getMessageId($response)
        );

        $this->sendPerformed($message);

        return $this->numberOfRecipients($message);
    }
public function send(Swift_Mime_SimpleMessage $message, &$failedRecipients = null): int
    {
        $this->beforeSendPerformed($message);

        $version = \PHP_VERSION ?? 'Unknown PHP version';
        $os      = \PHP_OS      ?? 'Unknown OS';

        $response = $this->client->post(
            $this->url,
            [
                'headers' => [
                    'X-Postmark-Server-Token' => $this->serverToken,
                    'Content-Type'            => 'application/json',
                    'User-Agent'              => "postmark (PHP Version: ${version}, OS: ${os})",
                ],
                'json' => $this->getMessagePayload($message),
            ]
        );

        $message->getHeaders()->addTextHeader(
            'X-PM-Message-Id',
            $this->getMessageId($response)
        );

        $this->sendPerformed($message);

        return $this->numberOfRecipients($message);
    }
{@inheritdoc}