Such notice to the Clearing Member shall be deemed to have been duly served, if delivered personally, immediately upon delivery, or if transmitted by facsimile, upon the generation of a successful transmission report from the facsimile machine, or if sent by prepaid post, two (2) days (for local mail) and seven (7) days (for overseas airmail) after posting and in proving the same it shall be sufficient to show that such notice, demand or communication was (in the case of delivery) duly addressed, or (in the case of sending by prepaid post) contained in an envelope which was duly addressed, stamped and posted, or (in the case of facsimile transmission) was duly transmitted from the despatching facsimile machine, as evidenced by a successful transmission report generated by such machine.