Processing and tracking of individual mail items processed through a document processing system such as a sorter or inserter utilize a mail item identifier that is unique with respect to each individual mail item. A mail item may have a postal authority approved code representing or containing its associated unique identifier. If not, an identifier is generated and a corresponding postal authority approved code is applied to the mail item. Processing entails associating the unique mail item identifier for each respective mail item with collected metadata for the respective mail item and storing the identifier and associated the metadata. In a sorter example, each mail item is sorted into a postal sort group, and the processing entails identifying the sort group to which each item is sorted and storing the identified sort in association with the unique mail item identifier.