Address Verification is the process of matching mailing list addresses against the address data file maintained by the US Postal Service. Verified lists save money by reducing the amount of mail returned as undeliverable. In some instances, the USPS may require proof of address verification as a condition for obtaining discounted mailing rates. In many cases, software used for verification is also used to correct, standardize, and enhance addresses. A list's National Deliverability Index (NDI) score indicates how well the list has been verified. See also Address Correction.
