Abstract: An improved electronic mailing apparatus and method is disclosed which provides customized zip to zone data reflecting variations in postal cost for a particular class of postal service. The apparatus includes a first memory means for storing standard zip to zone conversion data for existing, standard zip to zone conversion tables. A second memory means is provided for storing custom zip to zone conversion data for only a limited number of conversion tables. The custom data reflects postal cost variations in a particular class. A manually actuated switching means is provided for selectively addressing a memory sector of the second memory means. This sector stores custom conversion data for zip to zone conversion table corresponding to the zip code area where the meter is located. Memory requirements for custom data storage are thereby substantially reduced.