I recently signed up for a webpage. When I opened the customary "click this link to validate your email and pick a password" email my client notified me that the sender had requested a read receipt. I opted not to send one, and could complete the sign up anyway.
I was a bit surprised, since this has never happend to me before on a similar email. Being of the curious kind, I started to speculate why they request receipts, and how they could be used to enhance security. Maybe it is related to token invalidation, but how?
I fail to understand how they could be used. Perhaps you have any ideas?