law: Indian Post Office Act, 1898 
  4. Exclusive privilege of conveying letters reserved to
  
  the Government
  (1) Wherever within 5[India]
  
  posts or postal communications are established by Central Government, the
  
  Central Government shall have the exclusive privilege of conveying by post,
  
  from one place to another, all letters except in the following cases, and shall
  
  also have the exclusive privilege of performing all the incidental services of
  
  receiving, collecting, sending, dispatching and delivering all letters, except
  
  in the following cases that is to say:-
  (a) letters sent by a private friend in his
  
  way, journey or travel, to be delivered by him to the person to whom they are
  
  directed, without hire, reward or other profit or advantage for receiving,
  
  carrying or delivering them;
  (b) letters solely concerning the affairs of
  
  the sender or receiver thereof, sent by a messenger on purpose; and
  (c) letters solely concerning goods or
  
  property, sent either by sea or by land to be delivered with the goods or
  
  property which the letters concern, without hire, reward or other profit or
  
  advantage for receiving, carrying or delivering them :
  Provided that nothing in this
  
  section shall authorize any person to make a collection of letters excepted as
  
  aforesaid for the purpose of sending them otherwise than by post.
  (2) For the purposes
  
  of this section and section 5, the expression "letters" includes
  
  postcards.