I found some code that seems to work. Link is:
http://forum.x-cart.com/showthread.php?t=33757&highlight=news
<form action="news.php" name="subscribeform" method="post"><input type="hidden" name="subscribe_lng" value="{$store_language}" /><input type="text" name="newsemail" size="19" /><a href="javascript: document.subscribeform.submit();" js_to_href="Y">Subscribe</a></form>