A computer system for providing commercial advertisements, messages, coupons, or other types of information on letters, parcels, and other written communications to a receiver of the letter, parcel, or other written communications includes a processor coupled to the letter or parcel delivery network. The processor is configured to print or apply messages on letters or packages and to gather statistics regarding actions performed by the receivers of the communications; the processor is further configured to process the statistics to generate user data and to provide commercial advertisements to the receivers of letters and packages based on user data. The system also includes a processor coupled to the delivery network, and is configured to send advertisements to an apparatus to print or apply them on appropriate, targeted letters or packages during any of the phases of letter or parcel delivery, and to gather statistics regarding actions performed by the user. The processor will be configured to process statistics and to generate user data. The processor will further be configured to provide commercial advertisements to the user based on user data. The system is also used to calculate postage and apply postage indications to the letters or parcels.