Just like anything else that goes out of the bank, e.g. deposit statements, loan statements, etc., the bank logically has a reasonable time to forward checks, etc. to customers. Offering him a clear opportunity to credit a local account that he can draw on the day an interest payment is due is about the only offer you should make.
As far as the regulators are concerned, he has no case. They will get a kick out of the compliant, especially if he mentions that he is going to spend money and time bringing the bank down. That's a little mental!