Actually you don't because neither my gmail nor my Android mail clients will load images automatically and the emails sent are super suspicious looking, so I'd never enable it for them.
Also since you don't verify my SMS in any way, I might be using your service to send untraceable text spams to someone (perhaps someone I don't like who pays 10 cents per text) by sending gotcha mails to an inbox I control and then opening the mails.
Also, on the "Trap" page, I would highly recommend you remove the "Chase" and "PayPal" templates. Using those on your site and in the "trap" mails you send is possibly wire fraud and would certainly not be appreciated by either party, regardless of intent of this service.