I would like to override this file in my module but cannot find the reference name for
base/default/template/email/order/shipment/track.phtml
<layout version="0.1.0">
<????>
<reference name="????">
<action method="setTemplate">
<template>namespace/email/order/shipment/track.phtml</template>
</action>
</reference>
</????>
</layout>
what should i be replacing the question marks with?