In the epilogue, Herbie states that Perry called Della to get a federal court order to open Herbie's mailbox. But that call was made at Millie's office during the special audit session. Herbie wasn't there (he was in jail) and the call was never mentioned in court. Herbie should not have known about the call.
Millie Cornwall (Susan Bay Nimoy) and Herbert Cornwall (Martin West) are at their house. Millie picks up a cigarette and the phone rings. The cigarette is unlit; she takes the phone into the bedroom and closes the door. She is on camera while talking on the phone in the bedroom. When she hangs up and leaves the bedroom, the camera shot from the livingroom shows the cigarette is lit.