In a postal system, a delivery point (sometimes DP) is a single mailbox or other place at which mail is delivered.
In the US Postal System, a delivery point is a specific set of digits between 00 and 99 assigned to every address.
When combined with the ZIP + 4 code, the delivery point provides a unique identifier for every deliverable address served by the USPS.
The full rules for identifying the delivery point for a given address are specified in the USPS CASS Technical Guide.
New Zealand Post maintains an index of delivery points known as the National Postal Address Database (NPAD).