The document discusses various topics related to mail handling and routing in the postal system, including: 1. PIN (Postal Index Number) codes, PINPlus codes, and what each digit represents in terms of region and sorting office. 2. Due Mail and Sorting Lists which show mail receipt and dispatch schedules for each post office. 3. Revision of mail arrangements and routing when cases involve multiple divisions. 4. Addressing revenue leakage in mails and monitoring mail movement. 5. Centers of payment for haulage charges from railways and a sample bill.