The mail box rule survives.  Many leases, including the AIR leases, provide that notices are “deemed given” if they are “addressed as required herein and mailed with postage prepaid.” This case involved a certified mail letter, which does not require handing it to the post man, just “mailing it”.  The result is all a landlord or tenant needs to prove is that they mailed the letter, NOT actual receipt.  See Jenkins v. Tuneup Masters (1987) 190 Cal.App.3d 1