A method of detecting possible duplicate printing of postal indicia including receiving image data for printing a current postal indicium, determining a number of pixels that will be printed in a defined zone of the current postal indicium, obtaining stored pixel count data that includes one or more stored pixel counts that each represents a number of pixels that were printed in the defined zone of a previously printed postal indicium, determining whether the number of pixels equals any one of the stored pixel counts, initiating one or more fraud prevention actions if it is determined that the number of pixels equals any one of the stored pixel counts, and printing the current postal indicium if it is determined that the number of pixels does not equal any one of the stored pixel counts. Also, a mail processing system adapted to implement the method just described.