Proper service of said notice and resolution as provided in SMC 15.12.050 shall be by personal service upon the legal owner of record of such property if found within the City limits, or if he is not to be found within the City limits by depositing a copy of said notice and resolution in the United States mail postage prepaid. Said mail shall be registered or certified and addressed to said owner at the last known address of said owner as such person’s name and address appears in the last equalized assessment roll or as known to the City Clerk of the City of Sebastopol. The service is complete at the time of deposit. All other notices and resolutions required by this chapter shall be served as provided above, except that no personal service shall be required. The City Clerk or Building Official upon giving the notice as aforesaid shall file an affidavit thereof with the City Clerk, certifying as to the time and manner in which such notice was given. The failure of any owner or other person to receive such notice shall not affect in any manner the validity of any proceedings taken hereunder.