public function addTo(
        $to,
        $name = null,
        $substitutions = null,
        $personalizationIndex = null,
        $personalization = null
    ) {
        if ($to instanceof To) {
            $name = $to->getName();
            $substitutions = $to->getSubstitutions();
            $to = $to->getEmailAddress();
        }
        $this->addRecipientEmail(
            "To",
            $to,
            $name,
            $substitutions,
            $personalizationIndex,
            $personalization
        );
    }