What's the first really obvious clue that you're being conned by someone about winning the lottery and that they have the winnings for you, you just need to send them some money first?
Answer: You haven't bought a ticket.
That should be blatantly obvious enough to end the con attempt right there. But, for one poor fellow, it took him thousands of dollars before he realized he was being badly conned. Sadly, some people just aren't suspicious enough and con artists can reel them in and hook them for thousands of dollars. Hope and greed can tend to extinguish rationality sometimes.
The Detroit News: Police: Man loses thousands in Mega Millions fraud
It's a sad tale of how con artists take advantage of the gullible person's hopes (and greed) to lead them down the path to ruin. To add insult to injury, after milking and bilking him out of thousands of dollars, they have someone pretend to be a lawyer to approach him and claim he can stop the scam and recover the money...in return for more money of course. I'm quite sure he's not the only one who is getting nailed by these con artists.
Know that if you haven't bought a ticket, then you really cannot have won. This really cannot be overemphasized and should be an obvious stopper to this type of con attempt.
Know at least that the Mega Millions Game is not hosted overseas, which should have been one heckuva big clue even if you bypassed the previous quite obvious clue. Never send money to a stranger, especially overseas, for the promise that you will get more money in return. It doesn't work like that, at all, ever.
Know that the actual lottery commission will never require you to pay money in order to get your winnings. It doesn't work like that, at all, ever.