Bad news.

It looks like the fraudulent letter was also posted in the Yahoo and Lycos job search websites, also bearing your company name. Do a google search on your company name and you'll see the page hits.

Here's 2 websites with job scam information. The first link at blogspot.com contains links to government and law enforcement agencies. Note that both sites have already documented this bogus offer.

http://jobscams.blogspot.com/search?q=San+Wu+Rubber
http://forum.scambaits.com/showthread.php?p=16797

You should seek legal advice and understand what is necessary to protect the company's reputation and liability. Getting a disclaimer up on your website seems to be a necessary step. Also contact excite.com and try to get this perp's email address revoked.