Although I don't know what exactly went wrong between you and your husband, but I think the problem is now in you but not your husband.
Everyone makes mistake, its up to you to whether you want to be forgiving or not. If you have decided to forgive your husband, then keep bringing the subject up does NO good to recover your relationship.
Secondly, you might have thought that you were only asking him a simple question on that night, but I can tell you that it was a "leading question". No matter what the answer was, he would be in trouble anyway.
I am not trying to lecture you or taking side here but if you really want the relationship works, it takes two parties to do it. Your husband made a good step by communicating through e-mail, this can avoid a direct face to face conffrontation. By not replying the e-mail, you are sending him a non-forgiving message. So that's what I mean the problem is with you but not him anymore.
Once again, I am not trying to take side here and sorry to be so blunt.