Unless otherwise agreed by the parties, any written communication is deemed to have been received if it is delivered to the addressee personally or if it is delivered at his place of business, habitual residence, or mailing address, and the communication is deemed to have been received on the day it is so delivered.
Source:
Section 1297.31, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=CCP§ionNum=1297.31..