Mail is defined as paper documents sent in a standard sized, legal sized, or special handling envelope (Priority mail, express mail, etc.) with a weight of 16 ounces or less, and thickness of 1/2 inches or less.
Cal. Code Regs. Tit. 9, § 4415
Note: Authority cited: Sections 4005.1, 4027 and 4101, Welfare and Institutions Code. Reference: Section 5326, Welfare and Institutions Code.