public function addRecipient(Recipient $recipient){
        $this->to[] = array(
            'email' => $recipient->email,
            'name' => $recipient->name,
            'type' => $recipient->type
        );
        $this->merge_vars[] = array(
            'rcpt' => $recipient->email,
            'vars' => $recipient->getMergeVars()
        );
        $this->recipient_metadata[] = array(
            'rcpt' => $recipient->email,
            'values' => $recipient->getMetadata()
        );
        return $this;
    }