="Robert Munafo" <mrob27@gmail.com> I think that email clients should tell the (human) sender when the email has been opened by the (human) recipient.
Alas this isn't as simple as we'd hope. Such capability has been available in various guises for a long time; google [return receipt email] and see http://en.wikipedia.org/wiki/Return_receipt There's even an ad: "Receive court admissible certified delivery receipt." I've had several correspondents who've tried to use receipts regularly, but it seems to have generally fallen into disuse. There are many issues: For example if you don't get a receipt back for a while, should you resend, and risk spamming the recipient with multiple copies? Conversely, receipts are a way for spammers to confirm your address is "live" and thus to keep you on their junk mail list--which is then is of higher quality to re-sell to other spammers, etc. (Automatic download and rendering of embedded images in HTML messages has the same problem--the spammer gets the image download request back and thereby knows there's someone who opens messages at that eMail address.) I've also delayed allowing receipts to go back to avoid having the sender mistake "opened to glance at the summary" with "opened and actually read". Systems managed inside a single organization that can track message status as a bit of shared global state rather than by exchanging yet more messages are of course more tractable; the wilds of the web are a different story.