Since so many folks requested this feature, I thought it would be easier to simply write a forum post about it.
Now my eCommerce Express add-on supports an "email only" payment gateway. This is ideal if you don't need to take the payment straight away (or at all), or for offline payment methods such as: credit card via phone, invoice/account or bank transfer. TIP: If you want to accept payments via bank transfer, just provide the customer with your bank account details on your "thank you" page.
When an order is placed, an email is generated with the order details (and customer's IP address) and sent to your nominated email address. Easy!
When the "email only" gateway option is activated, you can also optionally choose to display extra fields in the checkout to capture the customer's name, address, phone and email. If you have basic HTML skills, you can also easily add as many custom fields to this form (eg. "customer account number").
Here's the marketplace link:
If you have any questions, just submit a support request.