Just one comment: Any serious ISP offering eCommerce hosting to their customers has this port open and knows how to protect their server without having to block all ports as a catch-all security measure.
If they won't open it, find a host who will. Otherwise you'll not be able to process shipping quotes and payments using 3rd-party services such as UPS, USPS, PayPal, Authorize.net, and more.
Oh, and for the record, Zen Cart has nothing to do with "zend.com"
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