I get these all the time just report them as junk and phishing scams to your email provider. If you had won a large sum of money then you would receive a letter or a phone call, they wouldn't tell you in an email alone! They usually want your bank details or for you to pay a fee for them to "release" your winnings. Stay well clear!

Another good way of telling if an opportunity is real is to check the DSA (direct selling Association) website (not sure if I m allowed to post a link). This organisation monitor companies and if they are a member of the DSA you are protected. Members of the DSA must abide by certain rules which can be read on their site. There is a list of DSA members on their site too.

I allow members of the DSA on my website but if they are not a member I throughly check them out to make sure they are not scams before they can get listed.