Said Chief Administrative Officer shall mail to the last known post office address of such person, in a registered package, a true and attested transcript of such copy so left with him or her, which shall be certified by him or her under the Seal of said City. Said Chief Administrative Officer shall certify under the Seal of said City all the Chief Administrative Officer's doings touching said copy so left with the Chief Administrative Officer by said sheriff or constable and shall attach to said certificate all registry receipts pertaining to such copy received by the Chief Administrative Officer.