Sounds like he just sucks at replying to e-mails. Some people are just like that. I think if it had anything to do with you, or if there were anything you could do about it, he would have outlined some general guidelines ("rules"). The "put 'reply' in the subject line" guideline would be helpful, except some people don't follow their own guidelines. It can be very frustrating. In my experience, the only thing you can do when someone else just sucks at something and it's beyond your ability to control or influence is either accept that they suck or find someone else.

My T, for instance, is constitutionally incapable of being on time. He's late, we talk about it, he apologizes, he's late again. I get angry about it, he apologizes, he's late again. I get depressed about it, he apologizes, then he's late again. The man could not be on time to save his life. It's just something he sucks at. But I don't want to find a new T, so I deal with it and don't even mention it anymore.

So, if e-mail is something you need from a T, you'd probably be best off looking for a new one. Whatever you decide to do, I wish you the best of luck.