California Code
ARTICLE 3 - Manner of Service of Summons
Section 415.40.

415.40. A summons may be served on a person outside this state in any manner provided by this article or by sending a copy of the summons and of the complaint to the person to be served by first-class mail, postage prepaid, requiring a return receipt. Service of a summons by this form of mail is deemed complete on the 10th day after such mailing.

(Amended by Stats. 1982, Ch. 249, Sec. 1.)