If you didn't buy a ticket you did not win! Lottery scammers think they are smart sending out letters or emails saying that you have won a large amount of money in a lottery. All they need from you is your bank account and personal information in order to deposit your substantial winnings. They are really looking to take your money. Do not send money or give out your personal information. Just the act of responding puts your name on their active list to receive more such fraudulent announcements. The best thing to do is turn the letter over to your local postmaster. If the U.S. Mail was used in the scam a complaint should be filed with the U.S. Postal Inspector.
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