If you want to notify customers by including the opt-in notice/disclosure as a statement stuffer, that's fine. It doesn't have to be in a separate mailing. For the customers who actually look at their statements, I'd suggest including a notice on the statement encouraging them to carefully read the disclosure.
If you include a letter of explanation, be careful. It is likely to qualify as an advertisement that "promotes the payment of overdrafts" under Regulation DD, § 230.11(b), and it will have to include the information required by that section. The notice/disclosure itself, because it is a required disclosure under §205.17 of Regulation E, does not trigger those advertising rules.
John S. Burnett
Fighting for Compliance since 1976
Bankers' Threads User #8