WP eStore is a very popular and great WordPress option for selling products via eCommerce. Out of the box they offer integration with MailChimp, AWeber, and GetResponse. Now you can more easily set it up with Interspire Email Marketer.
If you have been trolling around the Tips and Tricks discussion forums trying to figure out how to integrate Interspire Email Marketer as your autoresponder program we might be able to save you some time. Some amount of correct code tweaking would likely do the trick but here is a shortcut. You can force each eStore customer to be added as a user on your WordPress installation correct? Once the user is added as a user on WordPress our Interspire User Subscription Plugin for WordPress will do the rest. It will auto add the user as a contact on the Interspire Email Marketer contact list you designate and map over custom fields like billing address or phone number as well.