src/Viserio/Component/Mail/Transport/PostmarkTransport.php
protected function getMessagePayload(Swift_Mime_SimpleMessage $message): array
    {
        $payload = [];

        $payload = $this->processRecipients($payload, $message);
        $payload = $this->processMessageParts($payload, $message);

        return $this->processHeaders($payload, $message);
    }
protected function getMessagePayload(Swift_Mime_SimpleMessage $message): array
    {
        $payload = [];

        $payload = $this->processRecipients($payload, $message);
        $payload = $this->processMessageParts($payload, $message);

        return $this->processHeaders($payload, $message);
    }
Convert a Swift Mime Message to a Postmark Payload.

@param \Swift_Mime_SimpleMessage $message

@return array