There are so many internet scams that it's almost impossible to track them. The basic idea to remember is this: if you do not have a previous business relationship with the person sending you the email then assume it's a scam. Even then it's too easy to spoof someone's email address that you should be wary of anything that looks too good to be true.
Here's a good test: if the email seems to come from
[email protected] and the site to sign up is
www.scammerssite.ru/rogers.com ten that is a sure scam as the domains (the bit after the @ symbol) do not match up).
Don't buy anything by email, only buy on the web if
you started the transaction i.e. you went to their website.