Some facilities (such as amenities, airports, many companies) have their official **postal** address located not at the actuall address but in post office of the neighborhood (Post Office Box). They do not except to receive postal mail at physical address but in post office. This postal service is internationally known as Post Box (PO Box, BP - Boîte Postale, CP - Case Postale, Поштански преградак, Поштански фах, Поштански претинац).
The abbreviation for PO Boxes, customarily used on envelopes, should be present in the value of the tag (as there may be variants) : e.g.
addr:postbox=BP 57. This is needed because there are sometimes different types of postbox with different (but distinctive) abbreviations for special delivery servicing, each type with its own numbering.
See also contact:pobox=*