Cal. Prob. Code § 17205

If a trustee or beneficiary has served and filed either a notice of appearance, in person or by counsel, directed to the petitioner or the petitioner’s counsel in connection with a particular petition and proceeding or a written request for a copy of the petition, and has given an address to which notice or a copy of the petition may be mailed or delivered, the petitioner shall cause a copy of the petition to be mailed to that person within five days after service of the notice of appearance or receipt of the request.