Administrative postal codes are exceptions to geographic postal codes. It can be Poste restante, Competition post, Reply post/Free reply, Boxes or Bulk customer postcode.
Poste restante, the recipient can pick up the mail at Postnord's delivery office, without the addressee having a post office box. In the postcode system, there are a number of postcodes set aside for Poste restante.
Competition post is used for competitions where the answers come by physical letter and is most common in big cities.
Reply post/Frisvar is a service where the recipient pays the postage in arrears.