Electronically Delivering NSF & OD Notices

We've debated offering NSF or overdraft notices (the postcard when an account overdraws and overdraft protection kicks in) in electronic form rather than in writing via postcard or letter. Is there a regulation that NSF or overdraft notices are required to be delivered in writing to the customer? The transaction is clearly noted on the periodic statement as required. We feel that delivering electronically (via email or secure message) provides a more timely notice to our customers, therefore enabling them to prevent further overdrafts. However, we want to ensure we aren't violating any regulations that requires the notices be in writing. Please advise.