Answer:
Old versions of some regulations required alternative delivery methods but those have been removed. Assuming you followed E-SIGN requirements when you enrolled these consumers, you will have required that they keep their email address up to date and you told them how to change it with you.
You can revert to snail mail or a telephone call as a customer service, but it isn't a requirement any more than getting a snail mailed statement back marked "undeliverable."
First published on BankersOnline.com 4/2/12