Section 5(d) of the CAN-SPAM Act of 2003 makes it a crime to send to a “protected computer” (which as defined in section 3 of the statute effectively means any computer) a commercial e-mail “that includes sexually oriented material,” unless (1) “the recipient has given prior affirmative consent to receipt of the message,” or (2) the e-mail includes in its subject heading “the marks or notices prescribed by the [Federal Trade] Commission,” or (3) “the matter in the message that is initially viewable to the recipient includes only” —