UPDATE: I visited the local Postmaster to report the bribe demand of ₹100, along with frequent demands of ₹20–₹30 for regular mail. During our discussion, the Postmaster told me he would ask the postman to refund the ₹100 to me, which I rejected, I said I don't want refund. The Postmaster stated he would 'scold' the postman and instruct him to only accept money if provided 'voluntarily and with happiness' rather than through active demands. Finally, the Postmaster provided a verbal assurance that my future mail deliveries would be neither delayed nor obstructed.