A system and method of tracking a plurality of mail units during transfer from a source location to a destination. One embodiment is a method comprising associating information identifying the plurality of mail units with a radio frequency (RF) tag that identifies a carrier unit. The method further comprises storing said associated information in at least one of the RF tag and a computer memory. The method further comprises communicating with the RF tag to identify the location of the carrier unit. The method further comprises identifying the location of at least one of the plurality of mail units based at least in part on the location of the carrier unit. Another embodiment is a system configured to perform an embodiment of the method.