The method of sorting pre-sorted mailpieces in a postal sorting machine comprises the steps consisting in: detecting loading in the feed inlet of the machine of a batch of mailpieces pre-sorted by a mailer of the mailpieces on the basis of their delivery addresses; and, in response to said detection, loading, in the reference database of the address recognition system, a lexicon comprising the delivery addresses for only the pre-sorted mailpieces of the batch, and, by means of the monitoring and control unit and for each current mailpiece, comparing the result of the OCR reading with said delivery addresses of the lexicon so as to recognize the delivery address of said current mailpiece.