You say you found it on the internet, then mention email. Do you mean you found a website that has a contact address, or this deal was emailed to you? If it was emailed, you can pretty much ignore it. 99.9% of marketing in email is crap/fraud. If it was on a website, however...
What's the domain of the email? (i.e. @companyx.com) If it's Yahoo, Hotmail, Gmail, Lycos, etc., it's webmail. Seems fairly obvious to me. Another thing you should do is run a
WHOIS on the site. That should (with any luck) give you the owner's name, address, phone number; the works. You may just get a name, or nothing at all, however. Also, bear in mind it's possible he/she gave a fake name. Still, better than nothing.
Finally, common sense. Best tool of all. If it's too good to be true, it probably is.