To all the folks that suggest preventing opening of single-use links by robots.txt or user-agent detection etc: Just don't. There are dozens of tools at use thr

To all the folks that suggest preventing opening of single-use links by robots.txt or user-agent detection etc: Just don't. There are dozens of tools at use throughout the various stages of an email with URLs being delivered that will go out and fetch websites. You have to design any confirmation dialog so the user still has to click a button to confirm, otherwise any one of these tools might inadvertently trigger your confirmation.