send a polite message and and say that you send only to australia,

Not good advice, have absolutely no further contact with the scammer, they are after more than your money, that would just be a bonus. They are after getting your email address and any other details they can garner so they can target you later with phishing emails.

You can give ebay a call and tell them about this scammer, they are quite used to this type of con and should deregister the account pretty quickly.

They shouldn't have your email address as they would have made contact via eBay messages. The messages might appear in your regular email inbox, but that's because eBay sent them there, not the scammer.

As he hasn't actually bought anything from you, he shouldn't be able to contact you any more now you've added him to your blocked list. That is if you set up the blocks I mentioned in the buyer requirement section and ticked the very last box that says "don't allow blocked buyers to contact me".

Here's the link to the buyer requirements page in case I didn't explain it very well. http://offer.ebay.com.au/ws/eBayISAPI.dll?BuyerBlockPreferences

How did he get your email? If your only communication has been through ebay then they do not have your email address.

You have no need to be terrified, just extra cautious as far as emails are concerned. It is never a good idea to log into a site through a link in an email even if you think it is from someone you know or it looks like a genuine Paypal, bank or ebay email. Just make it a rule to never click on links and then sign in to a site, especially one that contains any financial details.

This gives you the full run down on how it works.

http://www.ebay.com.au/gds/Nigeria-is-a-scam-Fake-shipping-agent-Contact-Live-Help-/1000000001695207...