The subject of the email is Immigrant Visa Interview Appointment,
has the current date, the the case number & invoice number
and then the name of who is being interviewed.
They refer you to https://nvc.state.gov/prep
and ends with Immigrant Visa Interview Details, which includes
Interview Date/Time, the Interview location (city, country only), the NVC case number and Invoice ID, the Principal Applicant (name and address), preference category (currently CR1 though will be changing to IR1 before the interview) and the A#.
I don't think in general they do packet 3 and 4 anymore.