law: Indian Post Office Act, 1898 
  21. Power to make rules as to transmission by post of
  
  postal articles
   16  [(1) The Central
  
  Government may make rules as to the transmission of articles by post.
  (2) In particular and
  
  without prejudice to the generality of the foregoing power, such rules may-
  (a) specify articles
  
  which may not be transmitted by post;
  (b) prescribe
  
  conditions on which articles may be transmitted by post;
  (c) provide for the detention and disposal of
  
  articles in course of transmission by post in contravention of rules made under
  
  clause (a) or clause (b);
  (d) provide for the granting of receipts for,
  
  and the granting and obtaining of certificates of, posting and delivery of
  
  postal articles and the sums to be paid, in addition to any other postage, for
  
  such receipts and certificates; and
  (e) regulate covers, forms, dimensions, maximum
  
  weights, and enclosures, and the use of postal articles, other than letters,
  
  for making communications.]
  (3) Postal articles
  
  shall be posted and delivered at such times and in such manner as the Director
  
  General may, by order, from time to time appoint