Method allowing an authorized delivery person to drop off or pick up a parcel in a collective set of parcel boxes, preferably a mixed set of letterboxes and parcel boxes, equipped with a management unit, said set being located in an enclosed space accessible from the outside by way of a door or a similar closing means equipped with an electrically controlled locking means, in particular an entrance door to a building, said method consisting in temporarily authorizing access to a parcel box of this set in order to drop off or pick up a parcel by transmitting a unique code, the code being transmitted only after an automatic protocol for authenticating or accrediting said delivery person has been carried out, and the transmission of the code being used to unlock the door or the like, which method is characterized - in that said code is an access code with a limited validity duration and that is produced and transmitted by an external third party not related to the delivery person and chosen from the group consisting of the manufacturer, the manager and the owner of said set, - in that said access code is transmitted simultaneously to a portable communication means able to be consulted by the authorized delivery person and to the management unit of said set, immediately after said authorized delivery person has been identified and/or located close to said door or said set, - in that the unlocking of the door is either controlled automatically by the management unit upon reception of said code, and possibly checking that the authorized delivery person is present at or close to said door, or controlled by a control unit for controlling the locking means after said code has been provided to this unit by the delivery person or by their portable communication means, this unit also having received, beforehand, the same code transmitted by the external third party, and - in that the protocol for authenticating or accrediting a delivery person involved in dropping off or picking up a parcel in the set under consideration, and normally leading to the transmission of an access code at least to this set and to the portable communication means of said delivery person, and possibly also to the control unit for controlling the locking means of the door, is triggered i) either by the geolocation of the delivery person at or close to the geographical location of the set or of the door, possibly confirmed by detection that said delivery person is actually locally present in front of the door under consideration, or ii) by sending the image of encrypted visual information, such as a QR code, present on the door using the portable communication means of the delivery person, the sending of said code possibly, where applicable, furthermore being conditional upon a geolocation of the delivery person at or close to said door. - in that said code is an access code with a limited validity duration and that is produced and transmitted by an external third party not related to the delivery person and chosen from the group consisting of the manufacturer, the manager and the owner of said set, - in that said access code is transmitted simultaneously to a portable communication means able to be consulted by the authorized delivery person and to the management unit of said set, immediately after said authorized delivery person has been identified and/or located close to said door or said set, - in that the unlocking of the door is either controlled automatically by the management unit upon reception of said code, and possibly checking that the authorized delivery person is present at or close to said door, or controlled by a control unit for controlling the locking means after said code has been provided to this unit by the delivery person or by their portable communication means, this unit also having received, beforehand, the same code transmitted by the external third party, and - in that the protocol for authenticating or accrediting a delivery person involved in dropping off or picking up a parcel in the set under consideration, and normally leading to the transmission of an access code at least to this set and to the portable communication means of said delivery person, and possibly also to the control unit for controlling the locking means of the door, is triggered i) either by the geolocation of the delivery person at or close to the geographical location of the set or of the door, possibly confirmed by detection that said delivery person is actually locally present in front of the door under consideration, or ii) by sending the image of encrypted visual information, such as a QR code, present on the door using the portable communication means of the delivery person, the sending of said code possibly, where applicable, furthermore being conditional upon a geolocation of the delivery person at or close to said door.