Why I Didn't Answer Your Email

I get a lot of email, often while I'm in the middle of something thought-intensive. Managing interruptions and my attention means I have to triage emails based on only two things: who sent them, and what they wrote in the subject line. If I didn't answer yours, it's probably not personal: I probably glanced at it when it arrived and mentally put it on the “later” pile instead of the “now” pile, and “later” can be a very long time indeed.
If it was actually important that I read and respond to your email, and I couldn't tell that from the subject, what the hell is wrong with your writing? If you can live without my reply, well, you're smart: work something out without me. I'll probably think it's cool.