The CAN-SPAN Act is a federal law designed to stem the growing population of unwanted, malicious email in your inbox. It essentially tells you not to be deceptive and to allow people to unsubscribe from your email list.
The seven key provisions of CAN-SPAM
The email message must not have misleading of falsified header information ("From", "Reply-To", etc).
Don't use misleading subject lines.
Clearly identify that the email is an advertising message, and the message must come from a functioning return email address.
Commercial email must display the physical postal address of the sender.
Display a prominent notice that provides the recipient the opportunity to decline further emails from you (unsubscribe/opt-out).
Honor all opt-out requests within 10 business days.