California Code of Civil Procedure
Code of Civil Procedure section 415.40
ARTICLE 3. Manner of Service of Summons [415.10 - 415.95]
( Article 3 added by Stats. 1969, Ch. 1610. )
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.