How would you know if a lottery winning notification is a scam or not?

of course is a scam

You know if it is a scam if you did not play the lottery to begin with. If you do not play, you can not win. Any notification that you receive in emails or regular mail are frauds as well and anything coming from other countries is fraud. Others do this in an attempt to get you to buy their products but you actually do not win anything. I am not sure where you can report this but you could probably do a search on the internet.