Method of operating a lock of a letter and/or parcel box, hereinafter "box" for receiving and/or sending letters and/or parcels, which box includes: - a so-called service cylinder, which can be operated by a so-called service key, - a so-called owner's cylinder, which can be operated by a so-called owner's key, separate from said service key, the actuation of said cylinders being intended to achieve locking or unlocking of said lock, - an electronic device for controlling the locking and unlocking of said lock, said method of operating such a lock involving two different operating modes, namely - a first operating mode a) referred to as the receiving letters and/or parcels mode, in which: - a carrier requests, from a computer system, an authorization to open the box, - the computer system transfers the authorization request to an owner of the box, - the owner gives his authorization to the computer system, - the computer system provides to the carrier a service code, - the carrier enters the code on the box, - the carrier places a package in the box, - the computer system is informed of said deposit, - the computer system transmits the package deposit information to the owner, - the owner collects the package. - a second operating mode b) referred to as the sending letters and/or parcels mode, in which: - an owner places a package in the box, - a computer system is informed of said deposit, - the computer system informs a carrier of said deposit and provides a service code, - the carrier enters the code on the box, - the carrier removes the package from the box, - the computer system is informed of said withdrawal, the computer system transmits the package collection information to the owner, this operating method being characterized in that the electronic control device comprises: - an electrical sensor (22; 32) placed on each cylinder, - a numeric entry keypad, - an electric lock. and in that the electronic control device is configured such that: - actuation of the service cylinder only locks or unlocks said lock after entering a predefined code (X; Z), referred to as the service code, on the keypad of the electronic control device. - actuating the owner's cylinder or entering a predefined code, referred to as the owner's code, on the keypad of the electronic control device always locks or unlocks said lock. - a so-called service cylinder, which can be operated by a so-called service key, - a so-called owner's cylinder, which can be operated by a so-called owner's key, separate from said service key, the actuation of said cylinders being intended to achieve locking or unlocking of said lock, - an electronic device for controlling the locking and unlocking of said lock, said method of operating such a lock involving two different operating modes, namely - a first operating mode a) referred to as the receiving letters and/or parcels mode, in which: - a carrier requests, from a computer system, an authorization to open the box, - the computer system transfers the authorization request to an owner of the box, - the owner gives his authorization to the computer system, - the computer system provides to the carrier a service code, - the carrier enters the code on the box, - the carrier places a package in the box, - the computer system is informed of said deposit, - the computer system transmits the package deposit information to the owner, - the owner collects the package. - a second operating mode b) referred to as the sending letters and/or parcels mode, in which: - an owner places a package in the box, - a computer system is informed of said deposit, - the computer system informs a carrier of said deposit and provides a service code, - the carrier enters the code on the box, - the carrier removes the package from the box, - the computer system is informed of said withdrawal, the computer system transmits the package collection information to the owner, - a first operating mode a) referred to as the receiving letters and/or parcels mode, in which: - a carrier requests, from a computer system, an authorization to open the box, - the computer system transfers the authorization request to an owner of the box, - the owner gives his authorization to the computer system, - the computer system provides to the carrier a service code, - the carrier enters the code on the box, - the carrier places a package in the box, - the computer system is informed of said deposit, - the computer system transmits the package deposit information to the owner, - the owner collects the package. - a second operating mode b) referred to as the sending letters and/or parcels mode, in which: - a second operating mode b) referred to as the sending letters and/or parcels mode, in which: - an owner places a package in the box, - a computer system is informed of said deposit, - the computer system informs a carrier of said deposit and provides a service code, - the carrier enters the code on the box, - the carrier removes the package from the box, - the computer system is informed of said withdrawal, - an electrical sensor (22; 32) placed on each cylinder, - a numeric entry keypad, - an electric lock. - actuation of the service cylinder only locks or unlocks said lock after entering a predefined code (X; Z), referred to as the service code, on the keypad of the electronic control device. - actuating the owner's cylinder or entering a predefined code, referred to as the owner's code, on the keypad of the electronic control device always locks or unlocks said lock.