415.20.
(a) In lieu of personal delivery of a copy of the summons and complaint to the person to be served as specified in Section 416.10, 416.20, 416.30, 416.40, or 416.50, a summons may be served by leaving a copy of the summons and complaint during usual office hours in his or her the person to be served’s office or, if no physical address is known, at his or her their usual mailing address, other than a United States Postal Service post office box, with the person who is apparently in charge thereof, and by thereafter mailing a copy of the summons and complaint by first-class mail, postage prepaid to the person to be served at the place where a copy of the summons and complaint were left. When service is effected by leaving a copy of the summons and complaint at a mailing address, it shall be left with a person at least 18 years of age, who shall be informed of the contents thereof. Service of a summons in this manner is deemed complete on the 10th day after the mailing.(b) 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, in the presence of a competent member of the household or a person apparently in charge of his or her their office, place of business, or usual mailing address other than a United States Postal Service post office box, at least 18 years of age, who shall be informed of the contents thereof, and by thereafter mailing a copy of the summons and of the complaint by first-class mail, postage prepaid to the person to be served at the place where a copy of the summons and complaint were left. Service of a summons in this manner is deemed complete on the 10th day after the mailing.
(c) Notwithstanding subdivision (b), if the only address reasonably known for the person to be served is a private mailbox obtained through a commercial mail receiving agency, service of process may be effected on the first delivery attempt by leaving a copy of the summons and complaint with the commercial mail receiving agency in the manner described in subdivision (d) of Section 17538.5 of the Business and Professions Code.
(d) (1) Notwithstanding subdivision (b), if the only address reasonably known for the person to be served is a state prison or county jail, personal service of process shall be first be attempted in conformity with Section 4013.5 of the Penal Code. If personal service cannot be made, then substitute service may be made by leaving a copy of the summons and complaint with the warden, sheriff, or jailer in the manner described in Sections 4013 and 4013.5 of the Penal Code.
(2) If the person to be served has been transferred or released, a warden, sheriff, or jailer who receives a copy of the summons and complaint on that person’s behalf shall notify the server of that fact within 24 hours of the attempted service, and service shall not be considered effective.