This is a scam simply because I am not an Australian. This message may not be from whom it claims to be. Beware of following any links in it or of providing the sender with any personal information.
And that includes the attachments.
2010/2/10 [email protected]
Internal Revenue Service (IRS)
Australian Department of the Treasury

Dear Taxpayer,

After the last annual calculations of your fiscal activity we have
determined that you are eligible to receive a tax refund of $650.90.

Please submit the tax refund request and allow us 6-9 days in order
to process it.

A refund can be delayed for a variety of reasons.
For example submitting invalid records or applying after the deadline.

To access your tax refund, use the form attached to this email.

Regards,
Internal Revenue Service