The Federal Trade Commission has announced that as of May 19th, sexually explicit e-mails must contain the header "SEXUALLY-EXPLICIT:" and they can no longer contain graphic images. Users who want those images will have to click on hyper.
The FTC conducted a study this Spring and learned that 17% of all pornographic spam e-mails contain pornographic images. The FTC says from now on, such spammers have to include a postal address and a way to opt out of future mailings.
In some states, spammers have to have "ADV:ADULT" in the subject headers and this new FTC requirement would overrule such laws. Subject headers like these allow people to filter such e-mails out. Subject headers can no longer have graphic titles.