Mail processing methods and techniques for sorting and commingling mail from various mail sources including the tracking of the mail pieces through processing. Such tracking entails uniquely identifying each mail piece, received in batches from the mail sources, and recording the unique identification of each mail piece. The received mail is sorted and commingled in a first pass, to form first collections, and each first collection is loaded into a uniquely identified mail container. For each respective mail piece, the tracking entails recording an association of the unique identification of one of the mail containers into which it is likely the respective mail piece is sorted on the first pass. After processing is complete, postal and client reports can be adjusted based on actual first pass counts.