Commercial email with sexually oriented material carries "SEXUALLY-EXPLICIT: " as the first nineteen characters of its subject, in capitals, and nothing sexually oriented in the subject. What shows when it is opened is the electronic brown paper wrapper: the label, that it is an advertisement, how to opt out and a working opt-out address, your postal address, and any instructions to reach the material - after a clear line telling them to delete it instead. Mail only to people who gave prior affirmative consent is exempt. Paste the subject and the text that shows on opening; Brownpaper checks them.
Each campaign as it was approved: the subject, whether it went only to people who consented, who approved it and when it went.