Address Verification considers multiple factors when it calculates the mailability score. Address Verification bases the calculations principally on the Process Status Code value and the Element Result Status value for the address. Other factors that influence the mailability score include the granularity of the reference data for the country and the postal relevance of the address values.

For example, if Address Verification cannot verify input elements such as street and house number because the data is absent from the reference database, Address Verification reduces the mailability score value.

Additionally, country-specific factors influence the mailability score. For example, when you verify United States addresses, the mailability score calculations consider deliverability factors such as the R777 or R779 status of each address. An R777 or R779 (phantom route) address is an address in a location that is served by P.O. Box delivery although the mailing address contains valid street information. In such cases, Address Verification might assign an address a Process Status value of V4 or C4 and a Mailability Score value of 1, because the USPS does not deliver to the street address.