These spoofs are likely to be from a person whose real address is disguised, never respond to them just forward to spoof@ebay.com as Joey says.
If in doubt always check in your my messages if it is there it is probably valid, only answer them from there.
It is likely you are being targeted at random and unless the true identity can be determined such that thier ISP blocks them they will just keep coming.
A lot of spamming and spoof mails come from countries with turn a blind eye to this which includes Nigeria, China and some eastern European countries, so the likelihood of any action occurring to stop them is unlikely.
Even if blocked many others will take their place, that's life I'm afraid
