When using Google Checkout, you may receive some oddly formatted email addresses from your customers for the orders they place. These emails usually are along the lines of:
Seeing an email address in this format signifies that the customer has chosen to have their actual email address kept private. This is an option when the customer set up their Google Checkout account and is not controlled by any of the seller’s settings. This email address, however, is still valid. Any email sent to an address @checkout.google.com will be forwarded to the customer’s actual email address.