I don't mind too much if someone wants a confirmation that I've opened the mail - if it's mail from someone I intend to correspond with.
This Spam Arrest thing sends you an email with a "click here" in the body of the email. "Click here" is inherently an "unsafe action" if you're not confident that the person you're dealing with is running a clean machine. In the few cases where I've encountered it, it was on messages to "webmasters" to report problems with their websites. Without knowing who's the person running it, it does give pause whether one should be that concerned about whether their problems get solved...
In a couple of instances I've decide I was NOT that interested in being helpful, so at least it blocked my Spam.