A targeted mass mailing system and method including use of a pre-engineered subassembly. The subassembly is a unit of printable substrate which is processed according to at least one client-specified rule and which includes a unique identifier having associated code that drives manufacturing of the subassembly into a final assembly that constitutes at least one component of a mailing package, wherein the printable substrate may include at least one of paper, cardboard, plastic and foil, wherein the at least one component includes at least one mailing package insert and/or a mailing package container, wherein processing includes, but is not limited to, at least one of printing, folding, cutting, perforating, trimming, gluing, slitting, die-cutting, personalizing, matching, tipping, affixing, inserting, flipping, inverting, on-serting, labeling, enclosing and enveloping of the unit, and wherein the unique identifier is preferably removable.