The CAN-SPAM Act of 2003 establishes the United States' first national standards for the sending of commercial email and requires the Federal Trade Commission (FTC) to enforce these standards. The Act applies to all commercial email messages, which are defined as "any electronic mail message the primary purpose of which is the commercial advertisement or promotion of a commercial product or service," including email that promotes content on commercial websites. The CAN-SPAM Act prohibits email senders from using false or misleading header information, subject lines, or return email addresses. Email senders must also provide recipients with a clear and conspicuous opt-out notice in every email they send, and honor opt-out requests promptly. In addition, email senders cannot harvest email addresses from websites or use email addresses that have been collected through spyware. Finally, the CAN-SPAM Act prohibits email senders from using deceptive email marketing practices, such as using "bait" subject lines to entice recipients to open email, or sending email with hidden content that can only be revealed by opening the email.