Where is the requirement that an NSF/OD notice must be mailed to the customer if a check is returned?

Reg CC:

12 CFR § 229.33 Notice of nonpayment.

(d) Notification to customer. If the depositary bank receives a returned check or notice of nonpayment, it shall send or give notice to its customer of the facts by midnight of the banking day following the banking day on which it received the returned check or notice, or within a longer reasonable time.

This is for a chargeback, not an overdraft?

this is not part of an ODP program.

There is no requirement that you notify the customer that you've bounced a check.