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.