Unfortunately, as you may well have suspected, such a notification is a scam. The perpetrators send out a huge volume of such letters or emails, hoping that a small percentage of recipients will actually send $20.00 to "claim" their prize. The notification may even include a phony "check" with an illegible signature to entice you. It will even state "Not a check--Do not cash" under the "signature." Also, the prize amount is usually a very specific figure (such as $202,987.00 in your letter), that causes some to consider the announcement as credible. Such letters usually insist that you have an impending deadline and need to "act quickly" or forfeit the prize. Since the requested fee is relatively small, even some doubtful recipients risk $20 in hopes of receiving hundreds of thousands! Of course, legitimate sweepstakes to do insist on a fee from winners. Continue to disregard the notices and they will soon stop.
Hope this helps!