Lots of warning messages after clicking the confirm button

Thanks Jason,
That worked, I assume that I need to check for this on all pages that will use email in future.

Just one question related to my original question.
There are a number of columns in the orders table that I do not need and a few new ones that I do.
For instance I do not need:
OrderShipAddress
OrderShipAddress2
OrderCity
OrderState
OrderZip
OrderCountry
OrderFax
OrderShipping
OrderTax

Is it safe to remove these columns or do some of the helper files need them?

I will need to add columns for Cell, TakeoutTime and Date and some others.

Am I correct in assuming that after adding these fields to the checkout page, on the confirm page I will need to delete the session values that I don't need i.e.
<?php
if (!session_id()) session_start();
if($_SERVER["REQUEST_METHOD"] == "POST") {
$_SESSION["eCartCheckoutForm_fax"] = "".((isset($_POST["fax"]))?$_POST["fax"]:"") ."";
}
?>

and the hidden fields i.e.
<input type="hidden" name="shipping_fax" id="shipping_fax" value="<?php echo ((isset($_SESSION["eCartCheckoutForm_shipping_fax"]))?$_SESSION["eCartCheckoutForm_shipping_fax"]:"") ?>" />

and replace them with new ones for the new columns?

Regards, Paul