Answer:
There were rules in Reg E and Reg DD that required an institution to provide the statement through another address (paper or electronic) if the bank received notice that the original e-delivery failed. These rules were part of an interim rule implemented in 2001, but was never made mandatory and were removed in November 2007.
As to best practices, I still recommend attempting delivery through another channel if you receive notice that the original e-delivery failed. You would not always get that notice in event of a failure, but when you do, I think you have a duty to act on that.
First published on BankersOnline.com 5/25/09