Section 215(1) in The Indian Post Office Rules, 1933
(1)Gratuities shall be payable to the masters of the ships, not being mail ships, in respect of postal articles and mail bags or other containers received by them for conveyance on behalf of the Post Office at the following rates, namely:(a)Letter mails and empty bags shall be payable at the gross general cargorates as prevailing from time to time, subject to a reduction of 25%. In case of shipments to U.S.A., the payment shall be made at the non-contract rates, as prevailing from time to time subject to a reduction of 25%. On the lines where only net general cargo rates are quoted, payments shall be made on such net rates as prevailing from time to time subject to a reduction of 15%.(b)Parcel mail shall be paid for at two thirds the rates applicable to the letter mail.