Effective May 19, 2004, spam that includes sexually-oriented material must include the warning "SEXUALLY-EXPLICIT:" in the subject line, according to a rule adopted this year by the Federal Trade Commission. The CAN-SPAM Act, approved by Congress in 2003, directed the Commission to adopt a rule requiring a mark or notice to be included in spam that includes sexually-oriented content. Anyone in violation of the rule faces fines.

According to the Federal Trade Commission, the rule requires the mark to be included in both the subject line of any email message that contains sexually-oriented material, and in the equivalent of a "brown paper wrapper" in the body of the message. The "brown paper wrapper" is what an email recipient initially will see when opening a message containing sexually-oriented material. It will include the prescribed mark or notice, certain other specified information, and no other information or images.

To learn more about the rule, please visit http://www.ftc.gov/os/2004/04/040413adultemailfinalrule.pdf.