"Mystery Shopper" Scams
This scam can come in a variety of forms, but in this case, when the responder provides his/her address, the scammer sends a check for a large sum of money. The scammer is hoping you will deposit it, wire them a portion of the money (per whatever "agreement" was arranged), and leave you with a bounced check for which the bank expects you to pay the difference.
One way or another, the scammer is seeking to steal money from you. If you receive or have already received an email like this, DELETE it immediately. More information about this "Mystery Shopper" scam can also be found on the Federal Trade Commission's Web site.
Here's an example of this scam: