All are okay (except the last one which means in the mail, you have asked for some suggestion, correction, improvement or opinion etc and a little to needed after respond in third option). And, there are many ways to ask that.
I'll write here what I'd prefer.
I sent you an email but there's no reply.
This is one of the ways to convince everything what you want viz., You mailed, he received it, and somehow, there's no response. He might have missed it, didn't have time or might have considered not to reply or whatever the reason. If you stop after that sentence, anyone opposite to you is likely to clarify the matter. I think this is what you want ;)
Why haven't you answered it as stated in a comment is also correct but to me it seems a bit straightforward and somewhat ordering an answer ;) Anyway, that's my opinion though.
The fourth one doesn't fit here. If you are expecting a feedback, you must have asked about his opinion, suggestion, advice or the like. As you haven't specified the subject/context of that mail, I may not comment on this.