In a method of processing mailpieces, Customer Applied Identifier (CAI) codes are assigned to the mailpieces by a sender of the mailpieces, and are used by the postal operator while the mailpieces are passing through a postal sorting system. Said CAI codes are recorded in memory in the sorting system in correspondence with first digital fingerprints or image signatures prior to the first pass of the mailpieces through the postal sorting system. While a current mailpiece is passing through the sorting system in a first sorting pass, an image is formed of the surface of the mailpiece that bears a postal address block, and a current fingerprint and location information for locating said mailpiece in the sorting process is derived from the image of said mailpiece. A search is made for a match between said current fingerprint and a first fingerprint recorded in memory in order to retrieve a current CAI code with which said location information is.