law: The Joint-stock Companies Act, 1857
  LIV. Rules as to notices by letter.-
  Notices by letter shall be posted in such time as to admit of the letter being delivered in the due course of delivery within the period (if any) prescribed for the giving of such notice; and in proving such service it shall be sufficient to prove that such notice was properly directed, and that it was put into the Post Office at such time as aforesaid.