I don't know how it works but I know this just has to be Scam.
An Email saying I have a payment to Pay Pal and need to claim it, fair enough but I have no idea why.
Anyway I log into Pay Pal, the (genuine site) and sure enough there is a payment; 1 YEN !
That works out at 0.4 pence; I rejected it as somebody must be fishing for something and I would rather not confirm for them.
Whatever they are up to though it's certainly a clever idea !