I came across this information a while back while working on a project. I think you might find it interesting. At least it gives you an idea of what you should look for when replying to legitimate spam.

To avoid Spamming, here are the rules. A commercial email:
MUST NOT disguise the mail header (the digital path which it took to get to the recipient).
MUST NOT use a false or misleading “From” line.
MUST NOT use a deceptive “Subject” line.
MUST include a “clear and conspicuous identification that the message is an Advertisement or Solicitation.”
MUST include a “valid physical postal address of the sender.”
MUST include a “clear and conspicuous notice” that lets the recipient Opt-Out.
MUST include a functioning return address or automated way to Opt-Out. The Opt-Out mechanism must work for 30 days after the email was sent, and the sender has 10 days to remove someone that asks to be removed.
If a Spammer “harvests” (collects) email addresses off the Internet, or uses a computer program to randomly generate them, these are considered “Aggravated Violations” which can triple the fines. In the case of State-enforced civil actions, the statutory fines can increase from $250 to $750 per Spammed email address, with a cap increasing from $2,000,000 to $6,000,000, plus attorney fees.
The CAN-SPAM Act supercedes all existing State Spam laws, EXCEPT for the State laws that pertain to falsifying email addresses. Furthermore, the Federal government wants to be notified by any State that initiates a Spam lawsuit, and they reserve the right to join in and move the case to a regional US District Court.