Generally, I ignore all such challenges that reach me. I want to make sure people realize that they are interfering with mail they may want to receive when they set up tools like this. Sane people using such systems periodically skim their not-yet-approved mail queue to see if anything's trapped that they want to see. Less sane users of such systems... well, I generally don't care whether they see my note.
Today, though, I need this person to get my e-mail in a timely manner. See, she has something of mine that I need back, soon, and I don't want her to be able to say, "Oh, sorry, you didn't click the link, so I never got your mail."