SERVICE OF ORDER, DECISION, ETC. Any order or decision passed or any summons or notice issued under this Act, shall be
a) by tendering the order, decision, summons or notice or sending it by registered post to the person for whom it is intended or to his agent; or (b) if the order, decision, summons or notice cannot be served in the manner provided in clause (a), by affixing it on the notice board of the customs house.