The scam goes a bit like this...
You receive an email from a buyer who is interested in purchasing an item off you from outside eBay. They then offer you an amount for the item and the postage and send this amount to you in a fake email that is supposed to look like it has come from PayPal to say that the money has been deposited in your account.
Then you get some demanding emails to say that you haven't posted the item and bla, bla bla.
This may be convincing for some buyers to please be aware.
Thanks for looking!