Cal. Fam. Code § 2335.5
In a proceeding for dissolution of marriage or legal separation of the parties, where the judgment is to be entered by default, the petitioner shall provide the court clerk with a stamped envelope bearing sufficient postage addressed to the spouse who has defaulted, with the address of the court clerk as the return address, and the court clerk shall mail a copy of the request to enter default to that spouse in the envelope provided. A judgment of dissolution or legal separation, including relief requested in the petition, shall not be denied solely on the basis that the request to enter default was returned unopened to the court. The court clerk shall maintain any such document returned by the post office as part of the court file in the case.
Ca. Fam. Code § 2335.5