Is it not just that you develop a feeling of 'being rejected', when he ignores you, which in fact makes you email him in the hope of getting a response (and thus feeling less rejected)? You email since you hope he will respond as it would confirm for you that he cares and/or thinks about you and you would feel less 'rejected', in other words?

Not saying his lack of response should be interpreted as rejection of course. But I do recognize myself somewhat in your tendencies.
I also tend to think it is a very normal response to feel rejected when someone doesn't respond to your correspondence. In fact, responding to communication is a normal part of healthy human interaction. Plenty of literature about psychology describes how ignoring someone results in feelings of rejection. I'm not sure why these therapists try to tell their clients any different, when they are upset they are ignored. And why they make it as if the client has a problem if they feel rejected when their correspondence is met with silence. (Probably since it is more convenient for them?)

Either way, Laura, perhaps you experience the pain of what feels like a relationship that is onesided? If he were to respond to you regularly, showing interest in what you had written: do you think you would feel less inclined to email him at all? Or do you think it may actually lead to an increase in emails?