Section 415.20 (b) of the California Civil Code Of Procedure States: If a copy of the summons and complaint cannot with reasonable diligence be personally delivered to the person to be served, as specified in Section 416.60, 416.70, 416.80, or 416.90, a summons may be served by leaving a copy of the summons and complaint at the person’s dwelling house, usual place of abode, usual place of
business, or usual mailing address other than a United States Postal Service post office box,