3. For the purposes of this Act,-(a) a postal article shall be deemed to be in course of transmission by post from the time of its being delivered to a post office to the time of its being delivered to the addressee or of its being returned to the sender or otherwise disposed of under Chapter VII: (b) the delivery of a postal article of any description to a postman or other person authorised to receive postal articles of that description for the post shall be deemed to be a delivery to a post office: and(c) the delivery of a postal article at the house or office of the addressee, or to the addressee or his servant or agent or other person considered to be authorised to receive the article according to the usual manner of delivering postal articles to the addressee, shall be deemed to be delivery to the addressee.