One of the problems that I notice with email is that people often do not read them carefully, but they will go ahead and reply to them anyway, making either bland comments that do not move the ball forward at all (at the one extreme) or wildly inappropriate responses that complicate matters (at the other). It appears to me that such a responder's purpose is to assure the person who initiated the electronic conversation that the responder is right on top of things, that is, he is paying attention and really cares. Of course, that would be a lie.
If I am the initiator, I much prefer not to hear from a responder via email (or in any other context) until that person is ready to give my inquiry or comments thorough consideration before responding. If I don't hear from someone and I would like at least a confirmation that my message was received, then I may telephone or send an email seeking to set up a telephone call.
If one receives an email, but simply does not have the time to focus immediately, there is a risk that the initiator takes offense if one simply delays his response. The next thing we see is a repeat email from the initiator, barely masking annoyance. I think the answer to this is simply to respond to the initial email with an email that says something like "Thanks for your email. I expect to be able to focus on it in two [minutes, days, weeks, months, years]. I will telephone you about the matter, but will send you an email first to propose times for us to talk by telephone and see if we can settle on something convenient for us both. Adios."
This response, of course, does not refer to initiators whom I don't know or don't recognize and who give me no clue as to their identity. I will usually delete that kind. If I am not sure, then I will ask an assistant to respond to it and seek to determine whether the inquiry is a serious one.