A system and method is provided for printing an advertisement for insertion into a mailpiece. A customer computer system (150) communicates with a mailing service provider data processing system (80). The customer computer system (150) transmits to the mailing service provider data processing system (80) an electronic copy of at least one mailing address and at least one corresponding document to be mailed to the mailing address. The mailing address is cleansed as necessary by the mailing service provider data processing system (80), which then identifies a subset of third party advertisements available for insertion into a mailpiece to be assembled with the corresponding document. Enclosures to be printed from the subset of third party advertisements are selected by the customer or automatically by mailing service provider data processing system based on advertisement profiles. The corresponding document and the selected enclosures are printed and then inserted into an envelope to form the assembled mailpiece.