This is a very common scam - usually from 3rd world countries - and commonly from Aftrican 3rd World countries. They want to con you into fronting a small amount of money so as to get the big reward. I get maybe 2 or 3 of these a week.
Guess what happens after you front up the small amount of money asked? They ask for a little more, then a little more. Finally you get sick of it and just go away. If you try to prosecute them, you will find these governments are complicit in the scam.
There is another form of this - (if you occasionally advertise collector cars for sale in trade mags as I do)...A foreign "buyer" will immediately offer you your full asked price without even trying to bargain. He will ask for your bank routing so he can send a draft. Guess what they do with the bank routing? If you ask for a paper cashiers check, he will send one for about $3000 more than the price, and then ask you to remit about $2500 or so to a special overseas shipping agent out of the surplus. You can keep the rest for your effort.
The cashiers check is of course bogus, but it may take up to 15 days before it is obvious. A lot of people actually used their own money to pay the $2500 to the agent, who of course is part of the scam. There are variations of this for antiques and aircraft as well.
In all cases, they are just hoping that maybe one out of ten thousand they spam this out to will be silly enough to bite on it. Amazing that it still goes on after all the expose journalism on this subject. "Skeptical" can help you in more things than just the religious!!!
YF, James