If people decide that this is a good idea, I will have to an add automatic reply with something like

" You use this crappy service either because:

- You didn't spend enough time thinking about that email because you either want to edit it later, or delete it from my mail box

- You expect me to answer by some specific date, which implies you want me to be on your schedule.

- You want to violate my privacy by tracking if and when I read your email.

You also require me to use a third-party service to read your email as a text. That's unacceptable.

Remember you're trying to contact me, no the other way around. Send it plain text or don't send it at all. "