USPS Address Validation
To help prevent delivery errors ProductCart v5.2 (or greater) has integrated services from the United States Post Office to verify delivery addresses. While USPS Address Validation is turned on ProductCart checks addresses for errors. Errors such as missing information or mismatched city/state/zip code in an address can all be caught and corrected before as an order is placed.
Enabling USPS Address Validation
In your Control Panel under shipping select Add or View Shipping Services. Click United States Postal Service (USPS) to expand the section then click Edit next to USPS Shipping Settings. In the Address Validation section check the box next to Enable Address Validation and click submit.
This feature is only available while USPS is enabled and the address is within the United States.