Section 10(3) in The Bombay Motor Vehicles (Taxation of Passengers) Rules, 1958
(3)When the notice is served by post, the service shall be deemed to be effected by properly addressing, pre-paying and posting under a certificate of posting, the notice, and unless the contrary is proved; the service shall be deemed to have been effected at the time at which the notice would be delivered in the ordinary course of post.
