law: Indian Post Office Act, 1898 
  41. Duty of master of ship arriving at any port in  India in respect of postal articles and mail
  
  bags on board 
  (1) The master of a
  
  ship arriving at any port in 5[India] shall, without delay, cause
  
  every postal article or mail bag on board which is directed to that port and is
  
  within the exclusive privilege conferred on the Central Government by section
  
  4, to be delivered either at the post office at that port or to some officer of
  
  the Post Office authorized in this behalf by the Post Master General.
  (2) If there is on
  
  board any postal article or mail bag which is directed to any other place
  
  within 5[India] and is within the exclusive privilege aforesaid, the
  
  master shall, without delay, report the fact to the officer in charge of the
  
  post office at the port of arrival and act according to the directions he may
  
  receive from such officer, and the receipt of such officer shall discharge him
  
  from all further responsibility in respect of the postal article or mail bag.