What I am trying to say is that someone opening an e-mail should not be considered a failure. You can't expect people not to do this. All of this can be avoided

What I am trying to say is that someone opening an e-mail should not be considered a failure. You can't expect people not to do this. All of this can be avoided if you just use some service to proxy the images. So the IP would not be leaked because the proxy server is fetching the image and it could easily be doing this no matter what and even if it determines the message to be spam and user might not even see the e-mail.