Legal Question in Civil Litigation in California

It would be a futile gesture, since service by mail is not a lawful method of service on an in-state defendant. Hire a professional process server and have the defendant personally served.

I would suggest you look up and read Code of Civil Procedure sections 116.330 and 116.340 carefully, noting that the court clerk can serve the claim and order on the defendant by mail. The note 116.340(c) regarding proof of service. There is no provision for mail service by the plaintiff; only by the court clerk. However, mailing a follow-up copy is part of the routine for substitutued service as permitted under 116.340(a)(3).