Wherever notice is required to be given under a provision of the Municipal Code such notice may be given either by personal delivery thereof to the person to be notified or by disposition in the United States mail in a sealed envelope, postage prepaid, addressed to such person to be notified at his last known business or residence address as the same appears in the public records pertaining to the matter to which such notice is directed. Service by mail shall be deemed to have been completed at the time of disposition in the post office. Whenever a different method of serving notice is prescribed in the Municipal Code for a specific purpose, all notices for such purpose shall be given as prescribed in such Code. Proof of giving any notice may be made by the certificate of any officer or employee of the City or by affidavit of any person over the age of 18 years which shows service in conformity with the provisions of the Municipal Code or of any other law applicable to the subject matter concerned.